Causes and countermeasures for repeated outbreaks of hepatitis A among adults in Korea

Gender differences in hepatitis A seropositivity rates according to the Republic of Korea's vaccination policy

BACKGROUND

This study aimed to investigate differences in the anti-hepatitis A virus (HAV) antibody seropositivity rate by age and gender.

METHODS

We collected information on anti-HAV immunoglobulin G and immunoglobulin M status from samples submitted for HAV antibody testing in 2012-2022. A total of 1,333,615 cases were included in the analysis.

RESULTS

By age, the seropositivity rate was represented by a U-shaped curve, such that the rate was low for the group aged 20 to 39 years and higher in those who were younger or older. Over time, the curve shifted rightward, and the seropositivity rate declined gradually in the group aged 35 to 39 years and older. A gender-based difference in antibody seropositivity rate was especially noticeable in the group aged 20 to 29 years. This difference between genders widened in the participants' early 20s-when men in the Republic of Korea enlist in the military-and the divergence continued subsequently for older individuals.

CONCLUSION

These results indicate a higher risk of severe infection among older individuals and a gender-based difference in seroprevalence. Therefore, it is necessary to implement policies to promote vaccination in adults.

Investigating the spatio-temporal variation of hepatitis A in Korea using a Bayesian model

Hepatitis A is a water-borne infectious disease that frequently occurs in unsanitary environments. However, paradoxically, those who have spent their infancy in a sanitary environment are more susceptible to hepatitis A because they do not have the opportunity to acquire natural immunity. In Korea, hepatitis A is prevalent because of the distribution of uncooked seafood, especially during hot and humid summers. In general, the transmission of hepatitis A is known to be dynamically affected by socioeconomic, environmental, and weather-related factors and is heterogeneous in time and space. In this study, we aimed to investigate the spatio-temporal variation of hepatitis A and the effects of socioeconomic and weather-related factors in Korea using a flexible spatio-temporal model. We propose a Bayesian Poisson regression model coupled with spatio-temporal variability to estimate the effects of risk factors. We used weekly hepatitis A incidence data across 250 districts in Korea from 2016 to 2019. We found spatial and temporal autocorrelations of hepatitis A indicating that the spatial distribution of hepatitis A varied dynamically over time. From the estimation results, we noticed that the districts with large proportions of males and foreigners correspond to higher incidences. The average temperature was positively correlated with the incidence, which is in agreement with other studies showing that the incidences in Korea are noticeable in spring and summer due to the increased outdoor activity and intake of stale seafood. To the best of our knowledge, this study is the first to suggest a spatio-temporal model for hepatitis A across the entirety of Korean. The proposed model could be useful for predicting, preventing, and controlling the spread of hepatitis A.

Influence of temperature and precipitation on the incidence of hepatitis A in Seoul, Republic of Korea: a time series analysis using distributed lag linear and non-linear model

This study aimed to analyze the association between temperature and precipitation and the incidence of hepatitis A in Seoul, Korea, as meteorological factors may have different effects on specific diseases depending on the lifestyle in each region. Weekly cases of hepatitis A, weekly mean daily precipitation, and temperature data from 2016 to 2020 were analyzed. Quasi-Poisson-generalized linear models with time variable adjusted by spline function were used considering 0-6-week lags. The association of each variable and hepatitis A incidence was assessed by the single lag and the constrained distributed lag model. Multivariable distributed lag linear and non-linear models were used to develop models with significant independent variables. Weekly mean of daily mean temperature (Tmean) and maximum temperature (Tmax) were negatively associated with hepatitis A in the 6-week lag. Precipitation was negatively associated with hepatitis A in the 5- and 6-week lags. The multivariable model showed the negative association of Tmax, precipitation and hepatitis A in the 5- and 6-week lags. In the non-linear models, the incidence rate ratio (IRR) was the highest at a Tmax of 11 °C and decreased thereafter. IRR was the highest at 12 mm of precipitation and showed decrease pattern to 25 mm and then gradually increased in the 5- and 6-week lags. Identifying the impact of climate factors on hepatitis A incidence would help in the development of strategies to prevent diseases and indirectly estimate the impact of climate change on hepatitis A epidemiology.

An outbreak of hepatitis A associated with salted clams in Busan, Korea

OBJECTIVES

In July 2019, there were multiple reports on patients with hepatitis A among the visitors of a restaurant in Busan. The current study presents the results of an epidemiological investigation and outlines the supplementary measures that would help with hepatitis A control.

METHODS

A cohort study was conducted for all 2,865 customers who visited restaurant A from June to July. Using a standardized questionnaire, participants reported the presence of hepatitis A symptoms and whether they had consumed any of 19 food items. As for participants who had visited public health centers, their specimens were collected.

RESULTS

From the study cohort, 155 participants (5.4%) had confirmed hepatitis A. The epidemic curve was unimodal, and the median number of days from the restaurant visit to symptom onset was 31 days. A genotype analysis indicated that 89 of 90 tested patients had hepatitis A virus (HAV) genotype 1A. The results of a multivariate logistic regression analysis indicated that the ingestion of salted clams increased the risk of hepatitis A by 68.12 times (95% confidence interval [CI], 9.22 to 510.87). In an unopened package of salted clams found and secured through traceback investigation, HAV genotype 1A was detected.

CONCLUSIONS

To prevent people from ingesting uncooked clams, there needs to be more efforts to publicize the dangers of uncooked clams; the food sampling test standards for salted clams should also be expanded. Furthermore, a laboratory surveillance system based on molecular genetics should be established to detect outbreaks earlier.

Hepatitis A Outbreak in a Facility for the Disabled, Gyeonggi Province, Korea: An Epidemiological Investigation

Objectives:

The number of cases of hepatitis A virus (HAV) infections has sharply increased in Korea, especially among young adults. In this study, an HAV outbreak in a facility for disabled people was investigated, and we found epidemiological differences both between 2 different generations and between generally abled and disabled groups.

Methods:

We analyzed the incubation period and attack rate of an HAV outbreak and investigated the prevalence of HAV antibodies among the staff and residents of a facility for the disabled. We performed a retrospective cohort study during the HAV outbreak, which lasted from February 8 to 25, 2019, including examinations of HAV antibody tests and post-exposure HAV vaccination for the staff or residents of the facility.

Results:

There were 9 confirmed cases in 2 staff members and 7 residents. Among 53 people (30 staff and 23 residents), except for the 9 confirmed cases and 1 staff member with a known history of HAV infection, HAV seroprevalence was seen in 16.7% of the staff under 40 years of age and 95.2% of those over 40 years of age, while the corresponding rates in the residents were 0.0% and 58.8%, respectively.

Conclusions:

This result implies that it is necessary to prioritize HAV vaccination for vulnerable groups and workers of residential care facilities.

Epidemiology of viral disease outbreaks in Odisha, India (2010-2019)

Despite consistent public health efforts, the burden of viral disease in India remains high. The present study was undertaken to understand the aetiology, frequency and distribution of viral disease outbreaks in the state of Odisha between 2010 and 2019. This was a prospective study conducted at the Virology Research and Diagnostic Laboratory located at ICMR-Regional Medical Research Centre, Bhubaneswar, Odisha, wherein all the outbreaks of viral aetiologies were investigated and analysed to provide a comprehensive picture of the state of viral disease outbreaks in the region. A total of 191 suspected viral outbreaks were investigated by the team from VRDL during September 2010 and September 2019 reported from all the 30 districts of Odisha. Annual number of suspected cases ranged from 185 to 1002. The most commonly suspected outbreaks were of viral hepatitis (55 outbreaks; 1223 cases) followed by dengue (45 outbreaks; 1185 cases), chickenpox (30 outbreaks; 421 cases), viral encephalitis (27 outbreaks; 930 cases), measles (23 outbreaks; 464 cases), chikungunya (10 outbreaks; 593 cases) and rubella (1 outbreak; 60). The outbreaks peaked in frequency and intensity during the months of July and September. The epidemiology of viral disease outbreaks in the region is presented in the study. Health system preparedness based on evidence is essential for early detection and adequate response to such viral outbreaks.

Hepatitis A vaccination

Hepatitis A is an important public health issue worldwide. Hepatitis A vaccine (HepA) was first licensed in 1992. Both inactivated HepA (HepA-I) and live attenuated HepA (HepA-L) are highly immunogenic and well tolerated, and immune protection postvaccination can persist for at least 20 y. HepA is effective for both preexposure and postexposure prophylaxis, especially among children and young adults. The strategy of HepA vaccination varies in different countries and mainly includes vaccination among high-risk populations, regional childhood vaccination and universal childhood vaccination. The incidence of hepatitis A has decreased greatly in many countries in the last 30 y, but hepatitis A outbreaks frequently occur among high-risk populations and those who have not been covered by universal child vaccination programs in recent years. Disease surveillance and serosurveys are suggested to clarify the shift in the epidemiology of hepatitis A. The long-term persistence of immune protection after one dose of HepA should be further studied, as well as the cost-effective evaluation of different strategies of HepA vaccination. Based on this evidence, the recommendation on HepA vaccination should be put forward scientifically and updated in a timely and well-implemented manner.