Aspirin versus metformin in pregnancies at high risk of preterm pre-eclampsia in China (AVERT): protocol for a multicentre, double-blind, 3-arm randomised controlled trial

INTRODUCTION

Pre-eclampsia (PE) affects about 5% of Chinese pregnant women and is a major cause of maternal and perinatal morbidity and mortality. The first trimester screening model developed by the Fetal Medicine Foundation, which uses the Bayes theorem to combine maternal characteristics and medical history together with measurements of biomarkers, has been proven to be effective and has superior screening performance to that of the traditional risk factor-based approach for the prediction of PE. Prophylactic use of low-dose aspirin in women at risk for PE has resulted in a lower incidence of preterm-PE. However, there is no consensus on the preferred aspirin dosage for the prevention of preterm-PE. Evidence has also suggested that metformin has the potential benefit in preventing PE in pregnant women who are at high risk of the disorder.

METHOD AND ANALYSIS

We present a protocol (V.2.0, date 17 March 2022) for the AVERT trial, which is a multicentre, double-blinded, 3-arm randomised controlled trial (RCT) that uses an effective PE screening programme to explore the optimal dosage of aspirin and the role of metformin for the prevention of PE among high-risk pregnant women in China. We intend to recruit 66 000 singleton pregnancies without treatment of low-dose aspirin and metformin at 11-13 weeks' gestation and all eligible women attending for their first trimester routine scan will be invited to undergo screening for preterm-PE by the combination of maternal factors, mean arterial pressure and placental growth factor. Women found to be at high risk of developing preterm-PE will be invited to take part in the RCT. This study will compare the incidence of preterm-PE with delivery at <37 weeks' gestation, as the primary outcome, of three different interventional groups: (1) aspirin 75 mg daily, (2) aspirin 150 mg daily and (3) aspirin 75 mg with metformin 1.5 g daily. 957 participants per treatment group are required to detect a significant difference of 59% in the reduction of the incidence of preterm-PE with 80% power and type I error of 5%. Pregnancy and neonatal outcomes will be collected and analysed.

ETHICS AND DISSEMINATION

Ethical approval for the study was obtained from the Joint Chinese University of Hong Kong-New Territories East Cluster Clinical Research Ethics Committee (CREC Ref. No. 2021.406) in Hong Kong and the Ethics Committee of each participating hospital in Mainland China. The study is registered at ClinicalTrials.gov. The results of the AVERT trial will be disseminated at international academic conferences and published in high-impact factor journals.

TRIAL REGISTRATION NUMBER

NCT05580523.

Metabolic dysfunction-associated profiles and subsequent site-specific risk of obesity-related cancers among Chinese patients with diabetes: a retrospective cohort study

OBJECTIVES

To compare metabolic dysfunction-associated profiles between patients with diabetes who developed different obesity-related site-specific cancers and those who remained free of cancer during follow-up.

DESIGN

Retrospective cohort study.

SETTING

Public general outpatient clinics in Hong Kong.

PARTICIPANTS

Patients with diabetes without a history of malignancy (n=391 921).

PRIMARY OUTCOME MEASURES

The outcomes of interest were diagnosis of site-specific cancers (colon and rectum, liver, pancreas, bladder, kidney and stomach) during follow-up. Cox proportional hazards regression was applied to assess the associations between metabolic dysfunction and other clinical factors with each site-specific cancer.

RESULTS

Each 0.1 increase in waist-to-hip ratio was associated with an 11%-35% elevated risk of colorectal, bladder and liver cancers. Each 1% increase in glycated haemoglobin was linked to a 4%-9% higher risk of liver and pancreatic cancers. While low-density lipoprotein cholesterol and triglycerides were inversely associated with the risk of liver and pancreatic cancers, high-density lipoprotein cholesterol was negatively associated with pancreatic, gastric and kidney cancers, but positively associated with liver cancer. Furthermore, liver cirrhosis was linked to a 56% increased risk of pancreatic cancer. No significant association between hypertension and cancer risk was found.

CONCLUSIONS

Metabolic dysfunction-associated profiles contribute to different obesity-related cancer outcomes differentially among patients with diabetes. This study may provide evidence to help identify cancer prevention targets during routine diabetes care.

Exposure to Neighborhood Greenness and Hypertension Incidence in Adults: A Longitudinal Cohort Study in Taiwan

BACKGROUND

There are few studies on the health effects of long-term exposure to neighborhood greenness in a longitudinal setting, especially in Asian countries with high population densities.

OBJECTIVES

This study investigates the association between long-term exposure to neighborhood greenness and hypertension among adults in Taiwan.

METHODS

We selected 125,537 participants (≥ 18  years of age) without hypertension from Taiwan who had joined the standard medical examination program between 2001 and 2016. Neighborhood greenness was estimated using the normalized difference vegetation index (NDVI), derived from satellite images at a resolution of 250   m 2 . The 2-y average NDVI value within a 500 -m circular buffer around participants' residences was calculated. A time-varying Cox regression model was used to investigate the association between neighborhood greenness and incident hypertension. Mediation analyses were performed to examine whether the association was explained by air pollution, leisure-time physical exercise, or body mass index (BMI).

RESULTS

Compared with living in areas within the first quartile of neighborhood greenness, living in areas within the second, third, and fourth quartiles of neighborhood greenness was found to be associated with a lower risk of hypertension, with hazard ratios (HRs) and 95% confidence intervals (CIs) of 0.95 (95% CI: 0.91, 1.00), 0.95 (95% CI: 0.90, 0.99), and 0.93 (95% CI: 0.88, 0.97), respectively. Each 0.1-unit increase in the NDVI was associated with a 24% lower risk of developing hypertension (HR = 0.76; 95% CI: 0.66, 0.87), with this associations being stronger among males and those with higher education levels. This association was slightly mediated by BMI but not by air pollution or leisure-time physical exercise.

DISCUSSION

Our findings suggest the protective effects of neighborhood greenness on hypertension development, especially in males and well-educated individuals. Our results reinforced the importance of neighborhood greenness for supporting health. https://doi.org/10.1289/EHP13071.

CAGI, the Critical Assessment of Genome Interpretation, establishes progress and prospects for computational genetic variant interpretation methods

BACKGROUND

The Critical Assessment of Genome Interpretation (CAGI) aims to advance the state-of-the-art for computational prediction of genetic variant impact, particularly where relevant to disease. The five complete editions of the CAGI community experiment comprised 50 challenges, in which participants made blind predictions of phenotypes from genetic data, and these were evaluated by independent assessors.

RESULTS

Performance was particularly strong for clinical pathogenic variants, including some difficult-to-diagnose cases, and extends to interpretation of cancer-related variants. Missense variant interpretation methods were able to estimate biochemical effects with increasing accuracy. Assessment of methods for regulatory variants and complex trait disease risk was less definitive and indicates performance potentially suitable for auxiliary use in the clinic.

CONCLUSIONS

Results show that while current methods are imperfect, they have major utility for research and clinical applications. Emerging methods and increasingly large, robust datasets for training and assessment promise further progress ahead.

Inferring Incidence of Unreported SARS-CoV-2 Infections Using Seroprevalence of Open Reading Frame 8 Antigen, Hong Kong

We tested seroprevalence of open reading frame 8 antigens to infer the number of unrecognized SARS-CoV-2 Omicron infections in Hong Kong during 2022. We estimate 33.6% of the population was infected, 72.1% asymptomatically. Surveillance and control activities during large-scale outbreaks should account for potentially substantial undercounts.

The role of older adult-focused social vulnerability on the relationship between temperature and emergency department attendance in a subtropical Asian city

PURPOSE

Older adults exhibit a wide range of capabilities and vulnerabilities that affect their capacity to respond to heat. This study analysed the associations between hot temperatures and Accident & Emergency (A&E) attendance taking into account older adult-focused social vulnerability.

METHODS

Daily A&E attendance data of Young-old (65-74) and Old-old (75+) was obtained for Hong Kong 2010-2019 hot seasons and stratified into three Social Vulnerability Index (SVI) groups (Low, Moderate, High). Mean temperature (lag 0-2) was analysed on A&E attendance at each SVI using Generalized Additive Models and Distributed Lag Non-linear Models.

RESULTS

High temperatures were associated with increased same-day (lag 0) relative risk (RR) of A&E attendance for Young-old and Old-old in High SVI districts, with RR being 1.024 (95 % CI: 1.011, 1.037) and 1.036 (95 % CI: 1.018, 1.053), respectively. The Old-old living in Moderate and Low SVI districts also demonstrated increased RR of 1.037 (95 % CI: 1.028, 1.047) and 1.022 (95 % CI: 1.009, 1.036), respectively. Fewer emergency visits were found on the subsequent day (lag 1) of hot temperatures.

CONCLUSIONS

Older adults, both young-old and old-old, living in districts with higher social vulnerability tended to have increased risk of A&E attendance associated with same-day high temperature. With climate change and rapidly aging population, cities should prepare to meet needs of more vulnerable older adults in extreme heat.

Prevalence of oral human papillomavirus infection among the general adult population in Hong Kong

A cross-sectional study in 2021-23 collected oral rinse gargle samples from an human papillomaviruses (HPV) vaccine-naïve general adult population in Hong Kong. HPV was detected by a PCR using SPF10 primers, and genotyped by a linear array covering 25 genotypes. Epidemiologic information including sociodemographics, medical history, oral health, and sexual behavior were collected by a self-administered questionnaire. Altogether, 2323 subjects aged 18-75 (median 47) years with 50.1% male were recruited. The prevalence for oral HPV infection with all genotypes combined, high-risk, and low-risk genotypes was 1.5%, 0.7%, and 0.7%, respectively; and with no statistically significant difference between participant gender. The prevalence increased with age and was highest in women at 45-54 years (2.7% for all genotypes combined), and highest in men aged >64 years (4.1% for all genotypes combined). HPV52 was the most common genotype among all participants. Univariate analysis suggested more lifetime sexual or oral sexual partners as risk factors, but they did not reach statistical significance upon multivariate analysis; whereas higher educational level had an independent protective effect. To conclude, oral HPV prevalence increased with age in Hong Kong. Strategies to prevent oral HPV infection and the associated cancers are urgently needed.

Impact of the surge of COVID-19 Omicron outbreak on the intention of seasonal influenza vaccination in Hong Kong: A cross-sectional study

OBJECTIVE

To assess the intention of influenza vaccination during the Omicron pandemic of COVID-19 via a structured cross-sectional survey.

METHODS

A cross-sectional study was conducted in 1,813 Hong Kong quota-sampled adults between March and September 2022, when Hong Kong was experiencing an outbreak of Omicron infections. Questions included self-reported medical and vaccination history, and perceptions and intention of influenza vaccine. A multiple logistic regression analysis was conducted to identify significant factors associated with the vaccination intention.

RESULTS

Of the 1,813 participants, 25.8% (95% CI: 23.8%-27.8%) perceived positive impact of COVID-19 pandemic on their influenza vaccine willingness, which was more than two times the proportion of those who feel less likely to take influenza vaccine (11.5%, 95% CI: 10.1%-13.1%). Compared with males, females were less likely to receive influenza vaccine for 2022-23 influenza seasons (OR = 0.71, 95% CI: 0.52-0.95, p = 0.023) and had less impact on their influenza vaccine willingness (OR = 0.76, 95% CI: 0.59-0.99, p = 0.043). Participants older than 60 years old were related to a less positive impact compared with the youngers (OR = 0.53, 95% CI: 0.30-0.93, p = 0.028). Participants with experience of influenza vaccine uptake also showed a higher intention of seasonal influenza vaccination.

CONCLUSION

The public intention of influenza vaccine has been raised in Hong Kong. With the identified subgroups (e.g., female and elderly) and reasons for being reluctant to the influenza vaccination, policy makers should rectify common misperceptions in order to increase influenza vaccination coverage at the post COVID-19 phase.

A Machine Learning-Based Preclinical Osteoporosis Screening Tool (POST): Model Development and Validation Study

Background

Identifying persons with a high risk of developing osteoporosis and preventing the occurrence of the first fracture is a health care priority. Most existing osteoporosis screening tools have high sensitivity but relatively low specificity.

Objective

We aimed to develop an easily accessible and high-performance preclinical risk screening tool for osteoporosis using a machine learning-based method among the Hong Kong Chinese population.

Methods

Participants aged 45 years or older were enrolled from 6 clinics in the 3 major districts of Hong Kong. The potential risk factors for osteoporosis were collected through a validated, self-administered questionnaire and then filtered using a machine learning-based method. Bone mineral density was measured with dual-energy x-ray absorptiometry at the clinics; osteoporosis was defined as a t score of -2.5 or lower. We constructed machine learning models, including gradient boosting machines, support vector machines, and naive Bayes, as well as the commonly used logistic regression models, for the prediction of osteoporosis. The best-performing model was chosen as the final tool, named the Preclinical Osteoporosis Screening Tool (POST). Model performance was evaluated by the area under the receiver operating characteristic curve (AUC) and other metrics.

Results

Among the 800 participants enrolled in this study, the prevalence of osteoporosis was 10.6% (n=85). The machine learning-based Boruta algorithm identified 15 significantly important predictors from the 113 potential risk factors. Seven variables were further selected based on their accessibility and convenience for daily self-assessment and health care practice, including age, gender, education level, decreased body height, BMI, number of teeth lost, and the intake of vitamin D supplements, to construct the POST. The AUC of the POST was 0.86 and the sensitivity, specificity, and accuracy were all 0.83. The positive predictive value, negative predictive value, and F1-score were 0.41, 0.98, and 0.56, respectively.

Conclusions

The machine learning-based POST was conveniently accessible and exhibited accurate discriminative capabilities for the prediction of osteoporosis; it might be useful to guide population-based preclinical screening of osteoporosis and clinical decision-making.

Relationship between temperature variability and daily hospitalisations in Hong Kong over two decades

Background

Studies have highlighted the impacts of temperature variability (TV) on mortality from respiratory diseases and cardiovascular diseases, with inconsistent results specifically in subtropical urban areas than temperate ones. We aimed to fully determine TV-associated health risks over a spectrum of diseases and various subgroups in a subtropical setting.

Methods

Using inpatient data from all public hospitals in Hong Kong from 1999 to 2019, we examined the TV-hospitalisation associations by causes, ages, and seasons by fitting a quasi-Poisson regression. We presented the results as estimated percentage changes of hospitalisations per interquartile range (IQR) of TV.

Results

TVs in exposure days from 0-5 days (TV0-5) to 0-7 days (TV0-7) had detrimental effects on hospitalisation risks in Hong Kong. The overall population was significantly affected over TV0-5 to TV0-7 in endocrine, nutritional and metabolic (from 0.53% to 0.58%), respiratory system (from 0.38% to 0.53%), and circulatory systems diseases (from 0.47% to 0.56%). While we found no association with seasonal disparities, we did observe notable disparities by age, highlighting older adults' vulnerability to TVs. For example, people aged ≥65 years experienced the highest change of 0.88% (95% CI = 0.34%, 1.41%) in hospitalizations for injury and poisoning per IQR increase in TV0-4.

Conclusions

Our population-based study highlighted that TV-related health burden, usually regarded as minimal compared to other environmental factors, should receive more attention and be addressed in future relevant health policies, especially for vulnerable populations during the cold seasons.

Effectiveness of BNT162b2 and Sinovac vaccines against the transmission of SARS-CoV-2 during Omicron-predominance in Hong Kong: A retrospective cohort study of COVID-19 cases

BACKGROUND

In 2022, SARS-CoV-2 Omicron variants circulated globally, generating concerns about increased transmissibility and immune escape. Hong Kong, having an infection-naive population with a moderate 2-dose vaccine coverage (63% by the end of 2021), experienced a COVID-19 epidemic largely seeded by Omicron BA.2 variants that led to the greatest outbreak in the region to date. Little remains known about the protection of commonly-administered vaccines against transmission of Omicron BA.2 variants.

METHODS

In this retrospective cohort study, we identified 17 535 laboratory-confirmed COVID-19 cases using contact tracing information during the Omicron-predominant period between January and June 2022 in Hong Kong. Demographic characteristics, time from positive test result to case reporting, isolation, or hospital admission, as well as contact tracing history and contact setting were extracted. Transmission pairs were reconstructed through suspected epidemiological links according to contact tracing history, and the number of secondary cases was determined for each index case as a measurement for risk of transmission. The effectiveness of mRNA vaccine (BNT162b2) and inactivated vaccine (Sinovac) against transmission of BA.2 variants was estimated using zero-inflated negative binomial regression models.

RESULTS

Vaccine effectiveness against transmission for patients who received the 2-dose BNT162b2 vaccine was estimated at 56.2% (95% CI: 14.5, 77.6), 30.6% (95% CI: 13.0, 44.6), and 21.3% (95% CI: 2.9, 36.2) on 15 - 90, 91 - 180, and 181 - 270 days after vaccination, respectively, showing a significant decrease over time. For 3-dose vaccines, vaccine effectiveness estimates were 41.0% (95% CI: 11.3, 60.7) and 41.9% (95% CI: 6.1, 64.0) on 15 - 180 days after booster doses of Sinovac and BNT162b2, respectively. Although significant vaccine effectiveness was detected in household settings, no evidence of such protective association was detected in non-household settings for either Sinovac or BNT162b2.

CONCLUSION

Moderate and significant protection against Omicron BA.2 variants' transmission was found for 2 and 3 doses of Sinovac or BNT162b2 vaccines. Although protection by 2-dose BNT162b2 may evidently wane with time, protection could be restored by the booster dose. Here, we highlight the importance of continuously evaluating vaccine effectiveness against transmission for emerging SARS-CoV-2 variants.

Impact of climate change on dengue fever epidemics in South and Southeast Asian settings: A modelling study

The potential for dengue fever epidemic due to climate change remains uncertain in tropical areas. This study aims to assess the impact of climate change on dengue fever transmission in four South and Southeast Asian settings. We collected weekly data of dengue fever incidence, daily mean temperature and rainfall from 2012 to 2020 in Singapore, Colombo, Selangor, and Chiang Mai. Projections for temperature and rainfall were drawn for three Shared Socioeconomic Pathways (SSP126, SSP245, and SSP585) scenarios. Using a disease transmission model, we projected the dengue fever epidemics until 2090s and determined the changes in annual peak incidence, peak time, epidemic size, and outbreak duration. A total of 684,639 dengue fever cases were reported in the four locations between 2012 and 2020. The projected change in dengue fever transmission would be most significant under the SSP585 scenario. In comparison to the 2030s, the peak incidence would rise by 1.29 times in Singapore, 2.25 times in Colombo, 1.36 times in Selangor, and >10 times in Chiang Mai in the 2090s under SSP585. Additionally, the peak time was projected to be earlier in Singapore, Colombo, and Selangor, but be later in Chiang Mai under the SSP585 scenario. Even in a milder emission scenario of SSP126, the epidemic size was projected to increase by 5.94%, 10.81%, 12.95%, and 69.60% from the 2030s-2090s in Singapore, Colombo, Selangor, and Chiang Mai, respectively. The outbreak durations in the four settings were projected to be prolonged over this century under SSP126 and SSP245, while a slight decrease is expected in 2090s under SSP585. The results indicate that climate change is expected to increase the risk of dengue fever transmission in tropical areas of South and Southeast Asia. Limiting greenhouse gas emissions could be crucial in reducing the transmission of dengue fever in the future.

Effectiveness of mRNA and inactivated COVID-19 vaccines: A test-negative study in an infection-naïve Hong Kong population

OBJECTIVE

Assess real-world effectiveness of vaccines against COVID-19.

METHODS

A test-negative study was conducted in January-May 2022 during an Omicron BA.2 wave in Hong Kong. COVID-19 was identified by RT-PCR. 1-1 case-control matching was based on propensity score with vaccine effectiveness adjusted for confounders.

RESULTS

Altogether, 1781 cases and 1737 controls aged 3-105 years were analysed. The mean lag time from the last dose of vaccination to testing for SARS-CoV-2 was 133.9 (SD: 84.4) days. Two doses of either vaccine within 180 days offered a low effectiveness against COVID-19 of all severity combined (VEadj [95% CI] for BNT162b2: 27.0% [4.2-44.5], CoronaVac: 22.9% [1.3-39.7]), and further decreased after 180 days. Two doses of CoronaVac were poorly protective 39.5% [4.9-62.5] against severe diseases for age ≥ 60 years, but the effectiveness increased substantially after the third dose (79.1% [25.7-96.7]). Two doses of BNT162b2 protected age ≥ 60 years against severe diseases (79.3% [47.2, 93.9]); however, the uptake was not high enough to assess three doses.

CONCLUSIONS

The current real-world analysis indicates a high vaccine effectiveness of three doses of inactivated virus (CoronaVac) vaccines against Omicron variant, whereas the effectiveness of two doses is suboptimal.

Changes in all-cause and cause-specific excess mortality before and after the Omicron outbreak of COVID-19 in Hong Kong

Background

While coronavirus 2019 (COVID-19) deaths were generally underestimated in many countries, Hong Kong may show a different trend of excess mortality due to stringent measures, especially for deaths related to respiratory diseases. Nevertheless, the Omicron outbreak in Hong Kong evolved into a territory-wide transmission, similar to other settings such as Singapore, South Korea, and recently, mainland China. We hypothesized that the excess mortality would differ substantially before and after the Omicron outbreak.

Methods

We conducted a time-series analysis of daily deaths stratified by age, reported causes, and epidemic wave. We determined the excess mortality from the difference between observed and expected mortality from 23 January 2020 to 1 June 2022 by fitting mortality data from 2013 to 2019.

Results

During the early phase of the pandemic, the estimated excess mortality was -19.92 (95% confidence interval (CI) = -29.09, -10.75) and -115.57 (95% CI = -161.34, -69.79) per 100 000 population overall and for the elderly, respectively. However, the overall excess mortality rate was 234.08 (95% CI = 224.66, 243.50) per 100 000 population overall and as high as 928.09 (95% CI = 885.14, 971.04) per 100 000 population for the elderly during the Omicron epidemic. We generally observed negative excess mortality rates of non-COVID-19 respiratory diseases before and after the Omicron outbreak. In contrast, increases in excess mortality were generally reported in non-respiratory diseases after the Omicron outbreak.

Conclusions

Our results highlighted the averted mortality before 2022 among the elderly and patients with non-COVID-19 respiratory diseases, due to indirect benefits from stringent non-pharmaceutical interventions. The high excess mortality during the Omicron epidemic demonstrated a significant impact from the surge of COVID-19 infections in a SARS-CoV-2 infection-naive population, particularly evident in the elderly group.

Determining meteorologically-favorable zones for seasonal influenza activity in Hong Kong

Investigations of simple and accurate meteorology classification systems for influenza epidemics, particularly in subtropical regions, are limited. To assist in preparing for potential upsurges in the demand on healthcare facilities during influenza seasons, our study aims to develop a set of meteorologically-favorable zones for epidemics of influenza A and B, defined as the intervals of meteorological variables with prediction performance optimized. We collected weekly detection rates of laboratory-confirmed influenza cases from four local major hospitals in Hong Kong between 2004 and 2019. Meteorological and air quality records for hospitals were collected from their closest monitoring stations. We employed classification and regression trees to identify zones that optimize the prediction performance of meteorological data in influenza epidemics, defined as a weekly rate > 50^th percentile over a year. According to the results, a combination of temperature > 25.1℃ and relative humidity > 79% was favorable to epidemics in hot seasons, whereas either temperature < 16.4℃ or a combination of < 20.4℃ and relative humidity > 76% was favorable to epidemics in cold seasons. The area under the receiver operating characteristic curve (AUC) in model training achieved 0.80 (95% confidence interval [CI], 0.76-0.83) and was kept at 0.71 (95%CI, 0.65-0.77) in validation. The meteorologically-favorable zones for predicting influenza A or A and B epidemics together were similar, but the AUC for predicting influenza B epidemics was comparatively lower. In conclusion, we established meteorologically-favorable zones for influenza A and B epidemics with a satisfactory prediction performance, even though the influenza seasonality in this subtropical setting was weak and type-specific.

Comparing the incubation period, serial interval, and infectiousness profile between SARS-CoV-2 Omicron and Delta variants

BACKGROUND

In January 2022, the SARS-CoV-2 Omicron variant initiated major outbreaks and dominated the transmissions in Hong Kong, displacing an earlier outbreak seeded by the Delta variants. To provide insight into the transmission potential of the emerging variants, we aimed to compare the epidemiological characteristics of the Omicron and Delta variants.

METHODS

We analysed the line-list clinical and contact tracing data of the SARS-CoV-2 confirmed cases in Hong Kong. Transmission pairs were constructed based on the individual contact history. We fitted bias-controlled models to the data to estimate the serial interval, incubation period and infectiousness profile of the two variants. Viral load data were extracted and fitted to the random effect models to investigate the potential risk modifiers for the clinical viral shedding course.

RESULTS

Totally 14401 confirmed cases were reported between January 1 and February 15, 2022. The estimated mean serial interval (4.4 days vs 5.8 days) and incubation period (3.4 days vs 3.8 days) were shorter for the Omicron than the Delta variants. A larger proportion of pre-symptomatic transmission was observed for the Omicron (62%) compared to the Delta variants (48%). The Omicron cases had higher mean viral load over an infection course than the Delta cases, with the elder cases appearing more infectious than the younger cases for both variants.

CONCLUSION

The epidemiological features of Omicron variant were likely an obstacle to contact tracing measures, imposed as a major intervention in settings like Hong Kong. Continuously monitoring the epidemiological feature for any emerging SARS-CoV-2 variants in the future is needed to assist officials in planning measures for COVID-19 control. This article is protected by copyright. All rights reserved.

Dining-Out Behavior as a Proxy for the Superspreading Potential of SARS-CoV-2 Infections: Modeling Analysis

BACKGROUND

While many studies evaluated the reliability of digital mobility metrics as a proxy of SARS-CoV-2 transmission potential, none examined the relationship between dining-out behavior and the superspreading potential of COVID-19.

OBJECTIVE

We employed the mobility proxy of dining out in eateries to examine this association in Hong Kong with COVID-19 outbreaks highly characterized by superspreading events.

METHODS

We retrieved the illness onset date and contact-tracing history of all laboratory-confirmed cases of COVID-19 from February 16, 2020, to April 30, 2021. We estimated the time-varying reproduction number (Rt) and dispersion parameter (k), a measure of superspreading potential, and related them to the mobility proxy of dining out in eateries. We compared the relative contribution to the superspreading potential with other common proxies derived by Google LLC and Apple Inc.

RESULTS

A total of 6391 clusters involving 8375 cases were used in the estimation. A high correlation between dining-out mobility and superspreading potential was observed. Compared to other mobility proxies derived by Google and Apple, the mobility of dining-out behavior explained the highest variability of k (ΔR-sq=9.7%, 95% credible interval: 5.7% to 13.2%) and Rt (ΔR-sq=15.7%, 95% credible interval: 13.6% to 17.7%).

CONCLUSIONS

We demonstrated that there was a strong link between dining-out behaviors and the superspreading potential of COVID-19. The methodological innovation suggests a further development using digital mobility proxies of dining-out patterns to generate early warnings of superspreading events.

Relationship between meteorological variations, seasonal influenza, and hip fractures in the elderly: A modelling investigation using 22-year data

With the heavy negative health effect and economic burden of hip fractures in the elderly, the relationship of hip fractures with climate and seasonal influenza has not been quantified explicitly. In this study, we aim to make use of population-based data to evaluate the impact of meteorological factors and influenza activity on the hip fracture admissions for the elderly in Hong Kong from 1998 to 2019. Weekly numbers of admissions for the elderly due to hip fractures were used as the study outcome, and were matched with the meteorological factors included air temperature, relative humidity, solar radiation, and total rainfall. Strain-specific influenza-like illness-positive (ILI+) rates were employed as proxies for seasonal influenza activity. Quasi-Poisson generalized additive model in conjunction with distributed-lag non-linear model was used to elucidate the association of interest. According to the results, a total of 191,680 hip fracture admissions for the elderly aged ≥65 years were recorded over a 22-year span. The cumulative adjusted relative risks of hip fracture were 1.35 (95 % CI, 1.26-1.44) at the 5th percentile (15.05 °C) of air temperature, and 1.06 (95 % CI, 1.02-1.10) at the 95th percentile (20.91 MJ/m²) of solar radiation, with the reference value set to their respective medians. ILI+ rates were not associated with the risk of hip fracture. In the stratified analyses, a stronger association between cold condition and hip fracture was observed in males. Based on the results, strategies for preventing hip fractures with a focus on behaviors under unfavorable weather conditions should be targeted at individuals at risk.

A statistical framework for tracking the time-varying superspreading potential of COVID-19 epidemic

Timely detection of an evolving event of an infectious disease with superspreading potential is imperative for territory-wide disease control as well as preventing future outbreaks. While the reproduction number (R) is a commonly-adopted metric for disease transmissibility, the transmission heterogeneity quantified by dispersion parameter k, a metric for superspreading potential is seldom tracked. In this study, we developed an estimation framework to track the time-varying risk of superspreading events (SSEs) and demonstrated the method using the three epidemic waves of COVID-19 in Hong Kong. Epidemiological contact tracing data of the confirmed COVID-19 cases from 23 January 2020 to 30 September 2021 were obtained. By applying branching process models, we jointly estimated the time-varying R and k. Individual-based outbreak simulations were conducted to compare the time-varying assessment of the superspreading potential with the typical non-time-varying estimate of k over a period of time. We found that the COVID-19 transmission in Hong Kong exhibited substantial superspreading during the initial phase of the epidemics, with only 1 % (95 % Credible interval [CrI]: 0.6-2 %), 5 % (95 % CrI: 3-7 %) and 10 % (95 % CrI: 8-14 %) of the most infectious cases generated 80 % of all transmission for the first, second and third epidemic waves, respectively. After implementing local public health interventions, R estimates dropped gradually and k estimates increased thereby reducing the risk of SSEs to approaching zero. Outbreak simulations indicated that the non-time-varying estimate of k may overlook the possibility of large outbreaks. Hence, an estimation of the time-varying k as a compliment of R as a monitoring of both disease transmissibility and superspreading potential, particularly when public health interventions were relaxed is crucial for minimizing the risk of future outbreaks.

Relationship between antidepressants and severity of SARS-CoV-2 Omicron infection: a retrospective cohort study using real-world data

Background

Few studies have used real-world data to evaluate the impact of antidepressant use on the risk of developing severe outcomes after SARS-CoV-2 Omicron infection.

Methods

This is a retrospective cohort study using propensity-score matching to examine the relationship between antidepressant use and COVID-19 severity. Inpatient and medication records of all adult COVID-19 patients in Hong Kong during the Omicron-predominated period were obtained. Severe clinical outcomes including intensive care unit admission and inpatient death after the first positive results of reverse transcription polymerase chain reaction as well as a composite outcome of both were studied. Cox proportional hazard models were applied to estimate the crude and adjusted hazard ratios (HR).

Findings

Of 60,903 hospitalised COVID-19 patients admitted, 40,459 were included for matching, among which 3821 (9.4%) were prescribed antidepressants. The rates of intensive care unit admission, inpatient death, and the composite event were 3.9%, 25.5%, and 28.3% respectively in the unexposed group, 1.3%, 20.0%, and 21.1% respectively in the exposed group, with adjusted HR equal to 0.332 (95% CI, 0.245–0.449), 0.868 (95% CI, 0.800–0.942), and 0.786 (95% CI, 0.727–0.850) respectively. The result was generally consistent when stratified by selective serotonin reuptake inhibitors (SSRIs) and non-SSRIs. Antidepressants with functional inhibition of acid sphingomyelinase activity, specifically fluoxetine, were also negatively associated with the outcomes. The effect of antidepressants was more apparent in female and fully vaccinated COVID-19 patients.

Interpretation

Antidepressant use was associated with a lower risk of severe COVID-19. The findings support the continuation of antidepressants in patients with COVID-19, and provide evidence for the treatment potential of antidepressants for severe COVID-19.

Funding

This research was supported by Health and Medical Research Fund [grant numbers COVID190105, COVID19F03, INF-CUHK-1], Collaborative Research Fund of University Grants Committee [grant numbers C4139-20G], 10.13039/501100001809National Natural Science Foundation of China (NSFC) [71974165], and Group Research Scheme from The 10.13039/501100004853Chinese University of Hong Kong.

Estimating the serial intervals of SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 variants in Hong Kong

Empirical evidence on the epidemiological characteristics of the emerged SARS-CoV-2 variants could shed light on the transmission potential of the virus and strategic outbreak control planning. In this study, by using contact tracing data collected during an Omicron-predominant epidemic phase in Hong Kong, we estimated the mean serial interval of SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 variants at 2.8 days (95% credible interval [CrI]: 1.5, 6.7), 2.7 days (95% CrI: 2.1, 3.6), and 4.4 days (95% CrI: 2.6, 7.5), respectively, with adjustment for right truncation and sampling bias. The short serial interval for the current circulating variant indicated that outbreak mitigations through contact tracing and case isolation would be quite challenging.

Estimation of Vaccine Effectiveness of CoronaVac and BNT162b2 Against Severe Outcomes Over Time Among Patients With SARS-CoV-2 Omicron

IMPORTANCE

Few studies have evaluated the waning of vaccine effectiveness against severe outcomes caused by SARS-CoV-2 Omicron infection. Hong Kong is providing inactivated and mRNA vaccines, but the population had limited protection from natural infections before the Omicron variant emerged.

OBJECTIVE

To examine the change in vaccine effectiveness against hospitalization and mortality due to the Omicron variant over time.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study included adults with SARS-CoV-2 Omicron variant infection who died or were hospitalized in Hong Kong from January 1 to June 5, 2022 (ie, case participants), and adults with SARS-CoV-2 Omicron, sampled from the public health registry during the study period (ie, control participants), who were matched to case participants by propensity score.

EXPOSURES

Vaccination status of the individuals.

MAIN OUTCOMES AND MEASURES

Estimated vaccine effectiveness against death, death or hospitalization, and death among hospitalized patients. Vaccine effectiveness was calculated as 1 - adjusted odds ratio obtained by conditional logistic regression adjusted with covariates for each period following vaccination.

RESULTS

There were 32 823 case participants (25 546 [77.8%] ≥65 years; 16 930 [47.4%] female) and 131 328 control participants (100 041 [76.2%] ≥65 years; 66 625 [46.6%] female) in the sample analyzed for the death or hospitalization outcome. Vaccine effectiveness against death or hospitalization was maintained for at least 6 months after the second dose of both CoronaVac (74.0%; 95% CI, 71.8%-75.8%) and BNT162b2 (77.4%; 95% CI, 75.5%-79.0%) vaccines. Vaccine effectiveness against death in those aged 18 to 49 years was 86.4% (95% CI, 85.8%-87.0%) and 92.9% (95% CI, 92.6%-93.2%) for those receiving 2 doses of CoronaVac and BNT162b2, respectively, while for patients aged 80 years or older, it dropped to 61.4% (95% CI, 59.8%-63.2%) and 52.7% (95% CI, 50.2%-55.6%) for CoronaVac and BNT162b2, respectively. Nevertheless, overall vaccine effectiveness against death at 4 to 6 months after the third dose was greater than 90% for CoronaVac, BNT162b2, and the mixed vaccine schedule (eg, mixed vaccines: vaccine effectiveness, 92.2%; 95% CI, 89.2%-95.1%).

CONCLUSIONS AND RELEVANCE

While vaccines were generally estimated to be effective against severe outcomes caused by SARS-CoV-2 Omicron infection, this analysis found that protection in older patients was more likely to wane 6 months after the second dose. Hence, a booster dose is recommended for older patients to restore immunity. This is especially critical in a setting like Hong Kong, where third-dose coverage is still insufficient among older residents.

Association between cold weather, influenza infection, and asthma exacerbation in adults in Hong Kong

Despite a conspicuous exacerbation of asthma among patients hospitalized due to influenza infection, no study has attempted previously to elucidate the relationship between environmental factors, influenza activity, and asthma simultaneously in adults. In this study, we examined this relationship using population-based hospitalization records over 22 years. Daily numbers of hospitalizations due to asthma in adults of 41 public hospitals in Hong Kong during 1998-2019 were obtained. The data were matched with meteorological records and air pollutant concentrations. We used type-specific and all-type influenza-like illness plus (ILI+) rates as proxies for seasonal influenza activity. Quasi-Poisson generalized additive models together with distributed-lag non-linear models were used to examine the association. A total of 212,075 hospitalization episodes due to asthma were reported over 22 years. The cumulative adjusted relative risk (ARR) of asthma hospitalizations reached 1.15 (95 % confidence interval [CI], 1.12-1.18) when the ILI+ total rate increased from zero to 20.01 per 1000 consultations. Compared with the median temperature, a significantly increased risk of asthma hospitalization (cumulative ARR = 1.10, 95 % CI, 1.05-1.15) was observed at the 5^th percentile of temperature (i.e., 14.6 °C). Of the air pollutants, oxidant gas was significantly associated with asthma, but only at its extreme level of concentrations. In conclusion, cold conditions and influenza activities are risk factors to asthma exacerbation in adult population. Influenza-related asthma exacerbation that appeared to be more common in the warm and hot season, is likely to be attributable to influenza A/H3N2. The heavy influence of both determinants on asthma activity implies that climate change may complicate the asthma burden.

Estimation of the serial interval of monkeypox during the early outbreak in 2022

With increased transmissibility and novel transmission mode, monkeypox poses new threats to public health globally in the background of the ongoing COVID-19 pandemic. Estimates of the serial interval, a key epidemiological parameter of infectious disease transmission, could provide insights into the virus transmission risks. As of October 2022, little was known about the serial interval of monkeypox due to the lack of contact tracing data. In this study, public-available contact tracing data of global monkeypox cases were collected and 21 infector-infectee transmission pairs were identified. We proposed a statistical method applied to real-world observations to estimate the serial interval of the monkeypox. We estimated a mean serial interval of 5.6 days with the right truncation and sampling bias adjusted and calculated the reproduction number of 1.33 for the early monkeypox outbreaks at a global scale. Our findings provided a preliminary understanding of the transmission potentials of the current situation of monkeypox outbreaks. We highlighted the need for continuous surveillance of monkeypox for transmission risk assessment.

Impact of extreme weather on dengue fever infection in four Asian countries: A modelling analysis

The rapid spread of dengue fever (DF) infection has posed severe threats to global health. Environmental factors, such as weather conditions, are believed to regulate DF spread. While previous research reported inconsistent change of DF risk with varying weather conditions, few of them evaluated the impact of extreme weather conditions on DF infection risk. This study aims to examine the short-term associations between extreme temperatures, extreme rainfall, and DF infection risk in South and Southeast Asia. A total of 35 locations in Singapore, Malaysia, Sri Lanka, and Thailand were included, and weekly DF data, as well as the daily meteorological data from 2012 to 2020 were collected. A two-stage meta-analysis was used to estimate the overall effect of extreme weather conditions on the DF infection risk. Location-specific associations were obtained by the distributed lag nonlinear models. The DF infection risk appeared to increase within 1-3 weeks after extremely high temperature (e.g. lag week 2: RR = 1.074, 95 % CI: 1.022-1.129, p = 0.005). Compared with no rainfall, extreme rainfall was associated with a declined DF risk (RR = 0.748, 95 % CI: 0.620-0.903, p = 0.003), and most of the impact was across 0-3 weeks lag. In addition, the DF risk was found to be associated with more intensive extreme weathers (e.g. seven extreme rainfall days per week: RR = 0.338, 95 % CI: 0.120-0.947, p = 0.039). This study provides more evidence in support of the impact of extreme weather conditions on DF infection and suggests better preparation of DF control measures according to climate change.

Superspreading potential of COVID-19 outbreak seeded by Omicron variants of SARS-CoV-2 in Hong Kong

Using two early transmission chains in Hong Kong, the estimated R and k were 1.34 (95%CrI: 0.94-2.19) and 0.33 (95%CrI: 0.17-0.62) respectively, inferring 20.3% (95%CrI: 12.7%-29.6%) cases were responsible for 80% of the transmissions of the Omicron epidemic. Compared with Omicron BA.1, Omicron BA.2 had a greater superspreading potential.

Independent effect of weather, air pollutants, and seasonal influenza on risk of tuberculosis hospitalization: An analysis of 22-year hospital admission data

BACKGROUND

While influenza infections and environmental factors have been documented as potential drivers of tuberculosis, no investigations have simultaneously examined their impact on tuberculosis at a population level. This study thereby made use of Hong Kong's surveillance data over 22 years to elucidate the temporal association between environmental influences, influenza infections, and tuberculosis activity.

METHODS

Weekly total numbers of hospital admissions due to tuberculosis, meteorological data, and outdoor air pollutant concentrations in Hong Kong during 1998-2019 were obtained. All-type influenza-like illness positive (ILI+) rate and type-specific ILI+ rates were used as proxies for influenza activity. Quasi-Poisson generalized additive models together with distributed lag non-linear models were used to assess the association of interest.

RESULTS

A total of 164,116 hospital admissions due to tuberculosis were notified in public settings over a period of 22 years. The cumulative adjusted relative risk (ARR) of hospital admission due to tuberculosis was 1.07 (95% CI, 1.00-1.14) when the mean ambient temperature increased from 15.1 °C (the 5th percentile) to 24.5 °C (median). Short-term exposure to air pollutants was not found to be statistically significantly related to tuberculosis hospitalization. Accounting for the environmental covariates in the analysis, the cumulative ARR of tuberculosis admission was elevated to 1.05 (95% CI, 1.01-1.08) when the rate of ILI+ total increased from zero to 19.9 per 1000 consultations, the 95th percentile.

CONCLUSION

Our findings demonstrated that increased influenza activity and higher temperature were related to a higher risk of tuberculosis admissions. Stepping up the promotion of influenza vaccination, especially before the summer season, may lower the risk of tuberculosis infection/reactivation for vulnerable groups (e.g. elderly born before the launch of Bacillus Calmette-Guérin vaccination programme).

Association of weather, air pollutants, and seasonal influenza with chronic obstructive pulmonary disease hospitalization risks

The influences of weather and air pollutants on chronic obstructive pulmonary disease (COPD) have been well-studied. However, the heterogeneous effects of different influenza viral infections, air pollution and weather on COPD admissions and re-admissions have not been thoroughly examined. In this study, we aimed to elucidate the relationships between meteorological variables, air pollutants, seasonal influenza, and hospital admissions and re-admissions due to COPD in Hong Kong, a non-industrial influenza epicenter. A total number of 507703 hospital admissions (i.e., index admissions) and 301728 re-admission episodes (i.e., episodes within 30 days after the previous discharge) for COPD over 14 years (1998-2011) were obtained from all public hospitals. The aggregated weekly numbers were matched with meteorological records and outdoor air pollutant concentrations. Type-specific and all-type influenza-like illness positive (ILI+) rates were used as proxies for influenza activity. Generalized additive models were used in conjunction with distributed-lag non-linear models to estimate the associations of interest. According to the results, high concentrations of fine particulate matter, oxidant gases, and cold weather were strong independent risk factors of COPD outcomes. The cumulative adjusted relative risks exhibited a monotone increasing trend except for ILI+ B, and the numbers were statistically significant over the entire observed range of ILI+ total and ILI+ A/H3N2 when the reference rate was zero. COPD hospitalization risk from influenza infection was higher in the elderly than that in the general population. In conclusion, our results suggest that health administrators should impose clean air policies, such as strengthening emissions control on petrol vehicles, to reduce pollution from oxidant gases and particulates. An extension of the influenza vaccination program for patients with COPD may need to be encouraged: for example, vaccination may be included in hospital discharge planning, particularly before the winter epidemic.

Ratio of asymptomatic COVID-19 cases among ascertained SARS-CoV-2 infections in different regions and population groups in 2020: a systematic review and meta-analysis including 130 123 infections from 241 studies

INTRODUCTION

Asymptomatic infection of SARS-CoV-2 may lead to silent community transmission and compromise the COVID-19 pandemic control measures. We aimed to estimate the rate of asymptomatic COVID-19 from published studies and compare this rate among different regions and patient groups.

METHODS

In this systematic review and meta-analysis, electronic databases including Medline, Embase, PubMed and three Chinese electronic databases (Chinese National Knowledge Infrastructure [CNKI], WanFang Data and China Science, and Technology Journal Database [VIP]) were searched for literature published from 1 November 2019 to 31 December 2020. Original investigations with sample size (or number of subjects) not less than five were included for further analyses. Subgroup analyses were conducted according to different study types, study periods, geographical regions and patient demographics. The STATA (V.14.0) command 'metaprop' was implemented to conduct a meta-analysis of the pooled rate estimates of asymptomatic infections with exact binomial and score test-based 95% confidence interval (CI).

RESULTS

A total of 130 123 ascertained COVID-19 infections from 241 studies were included in this meta-analysis, including 31 411 asymptomatic infections. The overall rate of asymptomatic infections was 23.6% (18.5%-29.1%) and 21.7% (16.8%-27.0%) before and after excluding presymptomatic cases, respectively. Subgroup analysis showed that significantly higher in pregnant women (48.8%, 28.9%-68.9%), children (32.1%, 24.2%-40.5%), and studies reporting screening programmes (36.0%, 24.6%-48.1%) conducted on or after 1 March 2020 (42.5%, 33.4%-51.9%). In terms of geographical region, the rate was the highest in Africa (64.3%, 56.7%-71.6%), followed by America (40.0%, 27.4%-53.3%), Europe (28.1%, 19.0%-38.1%) and Asia (18.1%, 13.2%-23.5%).

CONCLUSION

We approximated that one-fifth of COVID-19 infections are asymptomatic throughout the course of infection. Public health policies targeting these high-risk groups may be recommended to achieve early identification and more stringent containment of the pandemic.

Characterization of Unlinked Cases of COVID-19 and Implications for Contact Tracing Measures: Retrospective Analysis of Surveillance Data

BACKGROUND

Contact tracing and intensive testing programs are essential for controlling the spread of COVID-19. However, conventional contact tracing is resource intensive and may not result in the tracing of all cases due to recall bias and cases not knowing the identity of some close contacts. Few studies have reported the epidemiological features of cases not identified by contact tracing ("unlinked cases") or described their potential roles in seeding community outbreaks.

OBJECTIVE

For this study, we characterized the role of unlinked cases in the epidemic by comparing their epidemiological profile with the linked cases; we also estimated their transmission potential across different settings.

METHODS

We obtained rapid surveillance data from the government, which contained the line listing of COVID-19 confirmed cases during the first three waves in Hong Kong. We compared the demographics, history of chronic illnesses, epidemiological characteristics, clinical characteristics, and outcomes of linked and unlinked cases. Transmission potentials in different settings were assessed by fitting a negative binomial distribution to the observed offspring distribution.

RESULTS

Time interval from illness onset to hospital admission was longer among unlinked cases than linked cases (median 5.00 days versus 3.78 days; P<.001), with a higher proportion of cases whose condition was critical or serious (13.0% versus 8.2%; P<.001). The proportion of unlinked cases was associated with an increase in the weekly number of local cases (P=.049). Cluster transmissions from the unlinked cases were most frequently identified in household settings, followed by eateries and workplaces, with the estimated probability of cluster transmissions being around 0.4 for households and 0.1-0.3 for the latter two settings.

CONCLUSIONS

The unlinked cases were positively associated with time to hospital admission, severity of infection, and epidemic size-implying a need to design and implement digital tracing methods to complement current conventional testing and tracing. To minimize the risk of cluster transmissions from unlinked cases, digital tracing approaches should be effectively applied in high-risk socioeconomic settings, and risk assessments should be conducted to review and adjust the policies.

Host inflammatory response is the major marker of severe respiratory syncytial virus infection in older adults

OBJECTIVES

We aim to study the viral kinetics and host inflammatory response of RSV infection in older adults, and their correlation with disease severity.

METHODS

We performed a prospective observational study in adults with RSV infection. We serially collected nasal-throat swabs for quantification of RSV-A and RSV-B viral load, and peripheral blood samples for measurement of cytokine/chemokine concentrations. The study endpoints were (i) requiring supplemental oxygen therapy, and (ii) non-invasive ventilation, intensive care, or died within 30 days of admission. We performed multivariable logistic regression models to identify independent variables for severe disease.

RESULTS

We enrolled 71 hospitalized patients and 10 outpatients treated for RSV infection (median age 75 years, 51% male, and 74% with comorbidities). Among hospitalized patients, 61% required supplemental oxygen therapy, and 18% had severe disease requiring non-invasive ventilation or intensive care, or died within 30 days. Inflammatory cytokine/chemokines IL-6, CXCL8/IL-8, CXCL9/MIG and CXCL10/IP-10 increased significantly during the acute phase of illness. IL-6 concentration was independently associated with severe disease after adjusting for confounding factors. RSV viral load was not associated with disease severity throughout the course of illness.

CONCLUSION

Host inflammatory response is a major marker of severe disease in older adults with RSV infection.

91Is rainfall associated with paediatric acute gastroenteritis in an affluent setting? A 21-Year Retrospective Investigation

Background

Although many literatures demonstrated heavy rainfall was associated with an increased risk of acute gastroenteritis via contaminated food and water, we hypothesized there is no association between rainfall and paediatric acute gastroenteritis in a setting with high-standard food and water hygiene.

Methods

Intestinal infection-related hospital admissions data during 1998-2018 for children under 5 years of age in Hong Kong were collected. Meteorological data were collected from the Hong Kong Observatory. A distributed lag nonlinear model was employed to examine the associations between meteorological factors and the risk of hospital admissions due to acute gastroenteritis.

Results

Rainfall did not exhibit a statistically significant association with the risk of paediatric admission due to acute gastroenteritis but low temperature, low and high relative humidity did. The risk was 6.3% higher (95% confidence interval: 0.3% to 12.6%) when temperature was at 15.1oC (i.e. the 5th percentile). The adjusted relative risk was statistically significantly higher when relative humidity was ≤73.0% or ≥ 84.0%.

Conclusions

Text: We suggest rainfall playing a minor role in disease transmission via contaminated food and water in affluent societies like Hong Kong. Instead, we speculate low temperature and humidity extremes have greater impact on transmission through increased stability and infectivity of enteric viruses.

Key messages

Weather plays a minor role in food and water contamination in affluent societies.

Low temperature and humidity extremes might improve survival of enteric viruses.

1474Meteorologically favourable zones for the activities of seasonal influenza A and B in Hong Kong

Background

Compared with temperate regions, the seasonality of influenza A and B in tropics and subtropics differs, for example, there are two peaks of influenza A virus activities in the summer and winter months, while influenza B peaked only in the winter months in Hong Kong. Given a potential effect from meteorological factors, we aim to develop a set of meteorologically favorable zones to predict the upsurge of activities of both influenza types.

Methods

Weekly numbers of laboratory-confirmed influenza A and B cases from January 1, 2004 to December 31, 2019 from cases admitted to three local hospitals were obtained. Meteorology data such as ambient temperature and relative humidity were collected from the Hong Kong Observatory. We employed a supervised discretization approach, classification and regression tree to identify the meteorologically favourable zones that optimize the prediction of influenza epidemics.

Results

The trained and validated areas-under-receiver-operating-characteristic-curve (AUROC) for the meteorologically favorable zones at 2-week ahead were 0.764 and 0.754 with a prediction sensitivity of 0.784 and 0.769, specificity of 0.616 and 0.635 respectively, showing a good performance. The prediction performances were generally similar among hospital-based prediction and the AUROCs kept &gt;0.7 across all study sites.

Conclusions

The preliminary findings provide a support for developing a local-based risk alert for the upsurge of influenza activities in order to promote a public awareness of the influenza risk.

Key messages

While influenza seasonality in subtropics and tropics is not as strong as that in temperate regions, meteorological factors still crucial in predicting influenza epidemics.

Relationship between acute kidney injury, seasonal influenza, and environmental factors: A 14-year retrospective analysis

Despite high incidence of acute kidney injury (AKI) among patients hospitalised for influenza, no previous work has attempted to analyse and quantify the association between the two. Herein, we made use of Hong Kong's surveillance data to evaluate the time-varying relationship between seasonal influenza and risk of AKI with adjustment for potential environmental covariates. Generalized additive model was used in conjunction with distributed-lag non-linear model to estimate the association of interest with daily AKI admissions as outcome and daily influenza admissions as predictor, while controlling for environmental variables (i.e. temperature, relative humidity, total rainfall, nitrogen dioxide, and ozone). Results suggested a positive association between risk of AKI admission and number of influenza hospitalisation cases, with relative risk reaching 1.12 (95% confidence interval, 1.10-1.15) at the 95th percentile. Using median as reference, an almost U-shaped association between risk of AKI admission and temperature was observed; the risk increased significantly when the temperature was low. While ozone was not shown to be a risk factor for AKI, moderate-to-high levels of nitrogen dioxide (50-95th percentile) were significantly associated with increased risk of AKI admission. This study mentioned the possibility that AKI hospitalisations are subject to environmental influences and offered support for a positive association between seasonal influenza and AKI occurrence in Hong Kong. Authorities are urged to extend the influenza vaccination program to individuals with pre-existing renal conditions to safeguard the health of the vulnerable. Given that adverse health effects are evident at current ambient levels of nitrogen dioxide, the government is recommended to adopt clean-air policies at the earliest opportunity to protect the health of the community.

Independent association between meteorological factors, PM2.5, and seasonal influenza activity in Hangzhou, Zhejiang province, China

BACKGROUND

Due to variations in climatic conditions, the effects of meteorological factors and PM2.5 on influenza activity, particularly in subtropical regions, vary in existing literature. In this study, we examined the relationship between influenza activity, meteorological parameters, and PM2.5 .

METHODS

A total of 20 165 laboratory-confirmed influenza cases in Hangzhou, Zhejiang province, were documented in our dataset and aggregated into weekly counts for downstream analysis. We employed a combination of the quasi-Poisson-generalized additive model and the distributed lag non-linear model to examine the relationship of interest, controlling for long-term trends, seasonal trends, and holidays.

RESULTS

A hockey-stick association was found between absolute humidity and the risk of influenza infections. The overall cumulative adjusted relative risk (ARR) was statistically significant when weekly mean absolute humidity was low (<10 µg/m3 ) and high (>17.5 µg/m3 ). A slightly higher ARR was observed when weekly mean temperature reached over 30.5°C. A statistically significantly higher ARR was observed when weekly mean relative humidity dropped below 67%. ARR increased statistically significantly with increasing rainfall. For PM2.5 , the ARR was marginally statistically insignificant. In brief, high temperature, wet and dry conditions, and heavy rainfall were the major risk factors associated with a higher risk of influenza infections.

CONCLUSIONS

The present study contributes additional knowledge to the understanding of the effects of various environmental factors on influenza activities. Our findings shall be useful and important for the development of influenza surveillance and early warning systems.

Long-term effectiveness of elderly health care voucher scheme strategies: a system dynamics simulation analysis

Background

The elderly healthcare voucher (EHCV) scheme is expected to lead to an increase in the number of elderly people selecting private primary healthcare services and reduce reliance on the public sector in Hong Kong. However, studies thus far have reported that this scheme has not received satisfactory responses. In this study, we examined changes in the ratio of visits between public and private doctors in primary care (to measure reliance on the public sector) for different strategic scenarios in the EHCV scheme.

Methods

Based on comments from an expert panel, a system dynamics model was formulated to simulate the impact of various enhanced strategies in the scheme: increasing voucher amounts, lowering the age eligibility, and designating vouchers for chronic conditions follow-up. Data and statistics for the model calibration were collected from various sources.

Results

The simulation results show that the current EHCV scheme is unable to reduce the utilization of public healthcare services, as well as the ratio of visits between public and private primary care among the local aging population. When comparing three different tested scenarios, even if the increase in the annual voucher amount could be maintained at the current pace or the age eligibility can be lowered to include those aged 60 years, the impact on shifts from public-to-private utilization were insignificant. The public-to-private ratio could only be marginally reduced from 0.74 to 0.64 in the first several years. Nevertheless, introducing a chronic disease-oriented voucher could result in a significant drop of 0.50 in the public-to-private ratio during the early implementation phase. However, the effect could not be maintained for an extended period.

Conclusions

Our findings will assist officials in improving the design of the EHCV scheme, within the wider context of promoting primary care among the elderly. We suggest that an additional chronic disease-oriented voucher can serve as an alternative strategy. The scheme must be redesigned to address more specific objectives or provide a separate voucher that promotes under-utilized healthcare services (e.g., preventive care), instead of services designed for unspecified reasons, which may lead to concerns regarding exploitation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11280-z.

Change in eating habits and physical activities before and during the COVID-19 pandemic in Hong Kong: a cross-sectional study via random telephone survey

BACKGROUND

Hong Kong is a densely populated city with a low incidence and mortality of coronavirus disease 2019 (COVID-19). The city imposed different levels of social distancing including, the closure of sports venues and restrictions on eateries. This inevitably affects the eating behaviour and physical activities of the population. We examined the changes in eating behavior and physical activities before and during the COVID-19 pandemic, and identified sociodemographic factors associated with the behavioral changes.

METHODS

This was a cross-sectional study via a random telephone survey of Chinese adults conducted in Hong Kong from May to June, 2020 - a period in which social distancing measures were being imposed. We measured the physical activity habits from four aspects and dietary consumption patterns from seven aspects before and during the pandemic based on the World Health Organization's guidelines and previous publications.

RESULTS

In total, 724 participants were recruited. Individuals were found to cook more frequently at home (p < 0.001) and order take-out (p < 0.001) during the COVID-19 pandemic. While no significant change in the frequency of fast food consumption was observed, we found significant increases in the frequency of eating fruits (p < 0.001) and vegetables (p = 0.004). The frequencies of walking, moderate-intensive sports, and high-intensity sports were significantly reduced (p < 0.001). We found that healthy lifestyle behaviors during the pandemic were negatively associated with participants' economic status.

CONCLUSIONS

Social distancing measures likely provided an opportunity for individuals to stay home and thus eat healthier. However, in a prolonged period of social restrictions, a lower physical activity level poses a risk to public health. Public health officials are thus advised to monitor physical health on a population-wide basis. The findings highlighted the importance of interventions tailored to individuals who have prolonged home stays - particularly for individuals in the low economic group.

A 21-year retrospective analysis of environmental impacts on paediatric acute gastroenteritis in an affluent setting

BACKGROUND

Extreme weather events happen more frequently along with global warming and they constitute a challenge for public health preparedness. For example, many investigations showed heavy rainfall was associated with an increased risk of acute gastroenteritis. In this study, we examined the associations between different meteorological factors and paediatric acute gastroenteritis in an affluent setting in China controlling for pollutant effects.

METHODS

Aggregated total weekly number of intestinal infection-related hospital admissions, and meteorological and air pollution data during 1998-2018 in Hong Kong were collected and analysed by a combination of quasi-Poisson generalized additive model and distributed lag nonlinear model. Study population was restricted to children under 5 years of age at the time of admission.

RESULTS

While heavy rainfall did not exhibit a statistically significant association with the risk of paediatric admission due to intestinal infections, low temperature and humidity extremes (both relative humidity and vapour pressure) did. Compared with the temperature at which the lowest risk was detected (i.e. 22.5 °C), the risk was 6.4% higher (95% confidence interval: 0.0% to 13.0% at 15.1 °C (i.e. the 5th percentile)). We also found the risk of paediatric admission was statistically significantly associated with an increase in the number of extreme cold days in a week over the study period.

CONCLUSION

Cold condition may have greater impact on disease transmission through increased stability and infectivity of enteric viruses in affluent settings like Hong Kong and thus resulted in an increased risk for paediatric acute gastroenteritis. On the contrary, an insignificant impact from heavy rainfall and high temperature may indicate a minor effect on disease transmission through bacterial growth in contaminated food and water. With the identified impacts of weather factors, extreme weather events are likely to distort the prevalence and seasonal pattern of diarrhoeal diseases in the future.

A global analysis of replacement of genetic variants of SARS-CoV-2 in association with containment capacity and changes in disease severity

OBJECTIVES

To examine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant replacement in association with containment capacity and changes in case fatality at country level.

METHODS

Altogether, 69 571 full SARS-CoV-2 genomes collected globally within the first 6 months of the pandemic were examined. The correlation between variant replacement and containment capacity was examined by logistic regression models using the WHO International Health Regulation (IHR) score, the Oxford COVID-19 Government Response Tracker (OxCGRT) and the vulnerability index INFORM as proxies, while correlation with changes in monthly crude case fatality ratios was examined by a mixed effect model.

RESULTS

At the global level, variant lineage G∗, characterized by the S-D614G mutation, replaced the older lineages L and S in March 2020. European countries-including Finland, France and Italy-were the first to reach a 50% increment of G∗, whereas only Singapore and South Korea had non-G∗ persisting throughout the first 6 months. Countries with higher IHR scores (β-coefficient -0.001, 95%CI -0.016, -0.001; p 0.034) and higher stringency indexes (OxCGRT) (β-coefficient -0.011, 95%CI -0.020, -0.001; p 0.035) were associated with lower levels of G∗ replacement, whereas higher vulnerability indexes (INFORM) (β-coefficient 0.049, 95%CI 0.001, 0.097; p 0.044) were associated with higher replacement levels. Crude case fatality ratio showed a positive correlation with G∗ replacement (β-coefficient: 0.034, 95%CI 0.011, 0.058; p 0.004), even after adjusting for testing capacity and other country-specific characteristics.

CONCLUSIONS

SARS-CoV-2 variant lineage G∗ (S-D614G) replaced older lineages more efficiently in countries with lower containment capacity, and its possible association with increased disease severity deserves further investigation.

Short-term association among meteorological variation, outdoor air pollution and acute bronchiolitis in children in a subtropical setting

OBJECTIVES

To examine the association among acute bronchiolitis-related hospitalisation in children, meteorological variation and outdoor air pollution.

METHODS

We obtained the daily counts of acute bronchiolitis-related admission of children≤2 years old from all public hospitals, meteorological data and outdoor air pollutants' concentrations between 1 January 2008 and 31 December 2017 in Hong Kong. We used quasi-Poisson generalised additive models together with distributed lag non-linear models to estimate the associations of interest adjusted for confounders.

RESULTS

A total of 29 688 admissions were included in the analysis. Increased adjusted relative risk (ARR) of acute bronchiolitis-related hospitalisation was associated with high temperature (ambient temperature and apparent temperature) and was marginally associated with high vapour pressure, a proxy for absolute humidity. High concentration of NO₂ was associated with elevated risk of acute bronchiolitis admission; the risk of bronchiolitis hospitalisation increased statistically significantly with cumulative NO₂ exposure over the range 66.2-119.6 µg/m³. For PM₁₀, the significant effect observed at high concentrations appears to be immediate but not long lasting. For SO₂, ARR increased as the concentration approached the 75th percentile and then decreased though the association was insignificant.

CONCLUSIONS

Acute bronchiolitis-related hospitalisation among children was associated with temperature and exposure to NO₂ and PM₁₀ at different lag times, suggesting a need to adopt sustainable clean air policies, especially to target pollutants produced by motor vehicles, to protect young children's health.

Assessing the impact of non-pharmaceutical interventions on the transmissibility and severity of COVID-19 during the first five months in the Western Pacific Region

While most countries in the Western Pacific Region (WPR) had similar trajectories of COVID-19 from January to May, their implementations of non-pharmaceutical interventions (NPIs) differed by transmission stages. To offer a better understanding for an implementation of multidisciplinary policies in COVID-19 control, we compared the impact of NPIs by assessing the transmissibility and severity of COVID-19 in different phases of the epidemic during the first five months in WPR. In this study, we estimated the piecewise instantaneous reproduction number (R_t) and the reporting delay-adjusted case-fatality ratio (dCFR) of COVID-19 in seven WPR jurisdictions: Hong Kong Special Administrative Region, Japan, Malaysia, Shanghai, Singapore, South Korea, and Taiwan. According to the results, implementing NPIs was associated with an apparent reduction of the piecewise R_t in two epidemic waves in general. However, large cluster outbreaks raised the piecewise R_t to a high level. We also observed relaxing the NPIs could result in an increase of R_t. The estimated dCFR ranged from 0.09% to 1.59% among the jurisdictions, except in Japan where an estimate of 5.31% might be due to low testing efforts. To conclude, in conjunction with border control measures to reduce influx of imported cases which might cause local outbreaks, other NPIs including social distancing measures along with case finding by rapid tests are also necessary to prevent potential large cluster outbreaks and transmissions from undetected cases. A comparatively lower CFR may reflect the health system capacity of these jurisdictions. In order to keep track of sustained disease transmission due to resumption of economic activities, a close monitoring of disease transmissibility is recommended in the relaxation phase. The report of transmission of SARS CoV-2 to pets in Hong Kong and to mink in farm outbreaks highlight for the control of COVID-19 and emerging infectious disease, the One Health approach is critical in understanding and accounting for how human, animals and environment health are intricately connected.

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Multidisciplinary One Health policies to combat COVID-19 are required in WPR.

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NPIs were associated with an apparent reduction in transmissibility of COVID-19.

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However, some large cluster outbreaks raised the transmissibility to a high level.

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We observed an increase in transmissibility when NPIs were partially lifted.

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A lower case-fatality ratio in WPR may reflect the health system capacity.

Transmissibility of coronavirus disease 2019 in Chinese cities with different dynamics of imported cases

BACKGROUND

Monitoring the reproduction number (Rt ) of the disease could help determine whether there is sustained transmission in a population, but areas with similar epidemic trends could have different transmission dynamics given the risk from imported cases varied across regions. In this study, we examined the Rt of coronavirus disease 2019 (COVID-19) by taking different dynamics of imported cases into account and compared the transmissibility of COVID-19 at different intervention periods in Hangzhou and Shenzhen.

METHODS

We obtained the daily aggregated counts of laboratory-confirmed imported and local cases of COVID-19 infections in Hangzhou and Shenzhen from January 1 to March 13, 2020. Daily Rt and piecewise Rt before and after Wuhan lockdown were estimated, accounting for imported cases.

RESULTS

Since the epidemic of COVID-19 in Shenzhen was dominated by imported cases, Rt was around 0.1 to 0.7 before the Wuhan lockdown. After the lockdown of Wuhan and the initialization of measures in response to the outbreak, local transmission was well-controlled as indicated by a low estimated value of piecewise Rt , 0.15 (95% CI [0.09-0.21]). On the contrary, Rt obtained for Hangzhou ranged from 1.2 to 4.9 with a piecewise Rt of 2.55 (95% CI [2.13-2.97]) before the lockdown of Wuhan due to the surge in local cases. Because of the Wuhan lockdown and other outbreak response measures, Rt dropped below unity in mid-February.

CONCLUSIONS

Even though Shenzhen had more cases than Hangzhou, local transmission did not sustain probably due to limited transmission from imported cases owing to the reduction in local susceptibles as residents left the city during Chunyun. The lockdown measures and local outbreak responses helped reduce the local transmissibility.

Association between obesity, common chronic diseases and health promoting lifestyle profiles in Hong Kong adults: a cross-sectional study

Background

Recent surveys revealed that the health status of many people from Hong Kong is far from ideal. Although non-communicable diseases are largely preventable, few relevant health promotion and disease prevention programs are available. Thus, we assessed the health indicators of Chinese adults in Hong Kong to investigate the relationship between obesity, common chronic diseases, and health-promoting lifestyle profiles to provide inspirations for decision makers in formulating targeted disease prevention and health management programs.

Methods

This is a secondary analysis of a data set of 270 community-dwelling Hong Kong adults who were within the eligible age range between 18 and 80 years without eye diseases that affect retinal photographs. The study exposure variable, health-promoting lifestyle profiles, was measured using the Health-Promoting Lifestyle Profile II (HPLP-II) questionnaire. The primary outcome variable, obesity, was defined using body mass index and waist-hip ratio. The secondary study outcome, estimated chronic diseases, including of anemia, chronic kidney disease, and cardiovascular disease, were estimated using automatic retinal image analysis from the retinal images. Data were analyzed using tests of proportion, the independent sample t-tests, Welch’s t-test, and binary logistic regression models.

Results

All HPLP-II subscales had positive responses (≥ 2.5). Significant differences were noted between men and women in the health responsibility and nutrition subscales (Health Responsibility: p = 0.059; Nutrition: p = 0.067). Regression models revealed that nutrition (adjusted odds ratio [AOR] = 0.41; p = 0.017), physical activity (AOR = 0.50; p = 0.015), interpersonal relations (AOR = 2.14; p = 0.016), and stress management (AOR = 2.07; p 0.038) were associated with obesity; while spiritual growth (AOR = 0.24; p = 0.077) and interpersonal relations (AOR = 5.06; p 0.069) were associated with estimated chronic kidney disease.

Conclusions

Improving health behaviors may control or alleviate the prevalence of obesity and chronic kidney disease. These findings could arouse concern about lifestyle behaviors and promote self-assessment of health-promoting lifestyles to the general public. The study also provided new insights into the relationship between the HPLP-II and other common chronic diseases that warrant further study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-09726-x.

Stringent containment measures without complete city lockdown to achieve low incidence and mortality across two waves of COVID-19 in Hong Kong

INTRODUCTION

An international city, Hong Kong, in proximity to the first epicentre of COVID- 19, experienced two epidemic waves with different importation pressure. We compared the epidemiological features of patients with COVID-19 in the context of containment policies between the first and second waves.

METHODS

We retrieved information on the first 1038 cases detected in Hong Kong (23 January to 25 April 2020) to analyse the epidemiological characteristics including age/gender-specific incidence, clustering, reproduction number (R_t ) and containment delay; in relation to the containment measures implemented. Factors associated with containment delay were evaluated by multiple linear regression analysis with age, gender, epidemic wave and infection source as covariates. A time series of 5-day moving average was plotted to examine the changes across the two epidemic waves.

RESULTS

The incidence and mortality (135.5 and 0.5 per 1 000 000 population) was among the lowest in the world. Aggressive escalation of border control correlated with reductions in R_t from 1.35 to 0.57 and 0.92 to 0.18, and aversions of 450 and 1650 local infections during the first and second waves, respectively. Implementing COVID-19 tests for overseas returners correlated with an upsurge of asymptomatic case detection, and shortened containment delay in the second wave. Medium-sized cluster events in the first wave were family gatherings, whereas those in the second wave were leisure activities among youngsters. Containment delay was associated with older age (adjusted OR (AOR)=1.01, 95% CI 1.00 to 1.02, p=0.040), male gender (AOR=1.41, 95% CI 1.02 to 1.96, p=0.039) and local cases (AOR=11.18, 95% CI 7.43 to 16.83, p<0.001), and with significant improvement in the second wave compared with the first wave (average: 6.8 vs 3.7 days). A higher incidence rate was observed for males, raising possibility of gender predilection in susceptibility of developing symptoms.

CONCLUSION

Prompt and stringent all-round containment strategies represent successful measures in pandemic control. These findings could inform formulation and implementation of pandemic mitigation strategies.