Imported dengue serotype 1 outbreak in a non-endemic region, China, 2017: A molecular and seroepidemiological study

Dengue epidemic in China before 1978

Dengue, an acute febrile disease transmitted by Aedes mosquitoes, is caused by the dengue virus (DENV), presenting a formidable challenge to global public health. By examining clues from ancient Chinese books and conducting a comprehensive review, this study elucidates the characteristics of potential dengue epidemics in China prior to 1978. This evidence indicates that China may not have experience dengue epidemics before 1840. During 1840-1949, however, it experienced a noticeable dengue occurrence and prevalence in the 1870s, 1920s, and 1940s. Then from 1949 to 1978, only sporadic reports were accounted. The disparity in the frequency of dengue occurrences across three time periods suggests that the persistent characteristic of dengue epidemics in China primarily arises from imported cases resulting from international exchanges, subsequently leading to local outbreaks influenced by global epidemic trend. This research offers a novel perspective on retrospectively examining the historical trajectory of dengue epidemics and provides valuable insights into exploration of DENV epidemic patterns.

Phylodynamics unveils invading and diffusing patterns of dengue virus serotype-1 in Guangdong, China from 1990 to 2019 under a global genotyping framework

BACKGROUND

The strong invasiveness and rapid expansion of dengue virus (DENV) pose a great challenge to global public health. However, dengue epidemic patterns and mechanisms at a genetic scale, particularly in term of cross-border transmissions, remain poorly understood. Importation is considered as the primary driver of dengue outbreaks in China, and since 1990 a frequent occurrence of large outbreaks has been triggered by the imported cases and subsequently spread to the western and northern parts of China. Therefore, this study aims to systematically reveal the invasion and diffusion patterns of DENV-1 in Guangdong, China from 1990 to 2019.

METHODS

These analyses were performed on 179 newly assembled genomes from indigenous dengue cases in Guangdong, China and 5152 E gene complete sequences recorded in Chinese mainland. The genetic population structure and epidemic patterns of DENV-1 circulating in Chinese mainland were characterized by phylogenetics, phylogeography, phylodynamics based on DENV-1 E-gene-based globally unified genotyping framework.

RESULTS

Multiple serotypes of DENV were co-circulating in Chinese mainland, particularly in Guangdong and Yunnan provinces. A total of 189 transmission clusters in 38 clades belonging to 22 subgenotypes of genotype I, IV and V of DENV-1 were identified, with 7 Clades of Concern (COCs) responsible for the large outbreaks since 1990. The epidemic periodicity was inferred from the data to be approximately 3 years. Dengue transmission events mainly occurred from Great Mekong Subregion-China (GMS-China), Southeast Asia (SEA), South Asia Subcontinent (SASC), and Oceania (OCE) to coastal and land border cities respectively in southeastern and southwestern China. Specially, Guangzhou was found to be the most dominant receipting hub, where DENV-1 diffused to other cities within the province and even other parts of the country. Genome phylogeny combined with epidemiological investigation demonstrated a clear local consecutive transmission process of a 5C1 transmission cluster (5C1-CN4) of DENV-1 in Guangzhou from 2013 to 2015, while the two provinces of Guangdong and Yunnan played key roles in ongoing transition of dengue epidemic patterns. In contextualizing within Invasion Biology theories, we have proposed a derived three-stage model encompassing the stages of invasion, colonization, and dissemination, which is supposed to enhance our understanding of dengue spreading patterns.

CONCLUSIONS

This study demonstrates the invasion and diffusion process of DENV-1 in Chinese mainland within a global genotyping framework, characterizing the genetic diversities of viral populations, multiple sources of importation, and periodic dynamics of the epidemic. These findings highlight the potential ongoing transition trends from epidemic to endemic status offering a valuable insight into early warning, prevention and control of rapid spreading of dengue both in China and worldwide.

Oral Complications related to tropical infectious Diseases: an introduction and analysis of survey data

BACKGROUNDS

The non-indigenous tropical infectious diseases that occur in the non-tropics arise from personnel communication between locals and visitors. Many of these infectious diseases involve oral complications. It is very important for practitioners to manage such cases based on a clear understanding of the association between tropical infectious diseases and oral health. In this study, we summarize the oral complications related to tropical infectious diseases and investigate the understanding of infectious disease practitioners in relation to the association between these conditions. In addition, we provide supportive advice to facilitate the oral management of tropical infectious diseases.

METHODS

First, we investigate the oral complications related to tropical infectious diseases by performing an appropriate literature search. Then, we analyzed the understanding of 207 Chinese practitioners specializing in infectious diseases in relation to the association between these two conditions by applying a bespoke online questionnaire.

RESULTS

Analysis revealed that the Chinese practitioners had very poor attitudes and knowledge relating to the association between tropical infectious diseases and oral health. Different backgrounds had no significant impact on the understanding of Chinese practitioners with regards to the association between tropical infectious diseases and oral health.

CONCLUSION

Many oral complications are related to tropical infectious diseases. The understanding of Chinese practitioners with regards to the association between infectious disease and oral health was very inadequate. It is essential to promote publicity and education relating to infectious tropical diseases and oral health.

Impact of climate change on SARS-CoV-2 epidemic in China

The outbreak and prevalence of SARS-CoV-2 have severely affected social security. Physical isolation is an effective control that affects the short-term human-to-human transmission of the epidemic, although weather presents a long-term effect. Understanding the effect of weather on the outbreak allow it to be contained at the earliest possible. China is selected as the study area, and six weather factors that receive the most attention from January 20, 2020 to April 30, 2020 are selected to investigate the correlation between weather and SARS-CoV-2 to provide a theoretical basis for long-term epidemic prevention and control. The results show that (1) the average growth rate (GR) of SARS-CoV-2 in each province is logarithmically distributed with a mean value of 5.15%. The GR of the southeastern region is higher than that of the northwestern region, which is consistent with the Hu Line. (2) The specific humidity, 2-m temperature (T), ultraviolet (UV) radiation, and wind speed (WS) adversely affect the GR. By contrast, the total precipitation (TP) and surface pressure (SP) promote the GR. (3) For every 1 unit increase in UV radiation, the GR decreases by 0.30% in 11 days, and the UV radiation in China is higher than that worldwide (0.92% higher per day). Higher population aggregation and urbanization directly affect the epidemic, and weather is an indirect factor.

The epidemiology and evolutionary dynamics of massive dengue outbreak in China, 2019

Introduction

In 2019, China experienced massive dengue outbreaks with high incidence and expanded outbreak areas. The study aims to depict dengue's epidemiology and evolutionary dynamics in China and explore the possible origin of these outbreaks.

Methods

Records of confirmed dengue cases in 2019 were obtained from the China Notifiable Disease Surveillance System. The sequences of complete envelope gene detected from the outbreak provinces in China in 2019 were retrieved from GenBank. Maximum Likelihood trees were constructed to genotype the viruses. The median-joining network was used to visualize fine-scale genetic relationships. Four methods were used to estimate the selective pressure.

Results

A total of 22,688 dengue cases were reported, 71.4% of which were indigenous cases and 28.6% were imported cases (including from abroad and from other domestic provinces). The abroad cases were predominantly imported from Southeast Asia countries (94.6%), with Cambodia (3,234 cases, 58.9%), and Myanmar (1,097 cases, 20.0%) ranked as the top two. A total of 11 provinces with dengue outbreaks were identified in the central-south of China, of which Yunnan and Guangdong provinces had the highest number of imported and indigenous cases. The primary source of imported cases in Yunnan was from Myanmar, while in the other ten provinces, the majority of imported cases were from Cambodia. Guangdong, Yunnan and Guangxi provinces were China's primary sources of domestically imported cases. Phylogenetic analysis of the viruses in outbreak provinces revealed three genotypes: (I, IV, and V) in DENV 1, Cosmopolitan and Asian I genotypes in DENV 2, and two genotypes (I and III) in DENV 3. Some genotypes concurrently circulated in different outbreak provinces. Most of the viruses were clustered with those from Southeast Asia. Haplotype network analysis showed that Southeast Asia, possibly Cambodia and Thailand, was the respective origin of the viruses in clade 1 and 4 for DENV 1. Positive selection was detected at codon 386 in clade 1.

Conclusion

Dengue importation from abroad, especially from Southeast Asia, resulted in the dengue epidemic in China in 2019. Domestic transmission between provinces and positive selection on virus evolution may contribute to the massive dengue outbreaks.

A unified global genotyping framework of dengue virus serotype-1 for a stratified coordinated surveillance strategy of dengue epidemics

BACKGROUND

Dengue is the fastest spreading arboviral disease, posing great challenges on global public health. A reproduceable and comparable global genotyping framework for contextualizing spatiotemporal epidemiological data of dengue virus (DENV) is essential for research studies and collaborative surveillance.

METHODS

Targeting DENV-1 spreading prominently in recent decades, by reconciling all qualified complete E gene sequences of 5003 DENV-1 strains with epidemiological information from 78 epidemic countries/areas ranging from 1944 to 2018, we established and characterized a unified global high-resolution genotyping framework using phylogenetics, population genetics, phylogeography, and phylodynamics.

RESULTS

The defined framework was discriminated with three hierarchical layers of genotype, subgenotype and clade with respective mean pairwise distances 2-6%, 0.8-2%, and ≤ 0.8%. The global epidemic patterns of DENV-1 showed strong geographic constraints representing stratified spatial-genetic epidemic pairs of Continent-Genotype, Region-Subgenotype and Nation-Clade, thereby identifying 12 epidemic regions which prospectively facilitates the region-based coordination. The increasing cross-transmission trends were also demonstrated. The traditional endemic countries such as Thailand, Vietnam and Indonesia displayed as persisting dominant source centers, while the emerging epidemic countries such as China, Australia, and the USA, where dengue outbreaks were frequently triggered by importation, showed a growing trend of DENV-1 diffusion. The probably hidden epidemics were found especially in Africa and India. Then, our framework can be utilized in an accurate stratified coordinated surveillance based on the defined viral population compositions. Thereby it is prospectively valuable for further hampering the ongoing transition process of epidemic to endemic, addressing the issue of inadequate monitoring, and warning us to be concerned about the cross-national, cross-regional, and cross-continental diffusions of dengue, which can potentially trigger large epidemics.

CONCLUSIONS

The framework and its utilization in quantitatively assessing DENV-1 epidemics has laid a foundation and re-unveiled the urgency for establishing a stratified coordinated surveillance platform for blocking global spreading of dengue. This framework is also expected to bridge classical DENV-1 genotyping with genomic epidemiology and risk modeling. We will promote it to the public and update it periodically.

Investigation of the understanding on tropical infectious diseases and oral health among dental professionals in China

Background

With the increasing exchange of domestic and international personnel, local infections of tropical infectious diseases are continuing in tropics and imported infections are emerging in non-tropics, some of which are accompanied by oral manifestations. Therefore, it is essential for dental professionals to identify the related oral manifestations, who are working for domestic medical service, international medical assistance, peace-keeping medical service or medical support of international joint military exercises. This study aims to investigate the attitude and knowledge of Chinese dental professionals on tropical infectious diseases and oral health, and to explore the difference between different genders, education backgrounds, professional identities, professional titles and tropics working experience.

Methods

Network questionnaire was used to evaluate the knowledge and attitude of 236 Chinese dental professionals towards tropical infectious diseases and oral health.

Results

The scores of the participants on tropical infectious diseases and oral health were quite low. Although working experience in the tropics partially affected the understanding, there was no difference between different genders, education backgrounds, professional identities and professional titles.

Conclusion

The understanding of dental professionals on tropical infectious diseases and oral health was insufficient. It is necessary to improve the clinical education and management specified with tropical infectious diseases and oral health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02250-x.

The Global Trends and Regional Differences in Incidence of Dengue Infection from 1990 to 2019: An Analysis from the Global Burden of Disease Study 2019

INTRODUCTION

Dengue, as a neglected tropical disease, brings a heavy socioeconomic burden. To provide tailored global prevention strategies, we analyzed the global trends and regional differences in incidence of dengue infection from 1990 to 2019.

METHODS

We obtained data on annual dengue episodes and incidence rates, which reflected the epidemic status of dengue infection from the 2019 Global Burden of Disease (GBD) Study. The changes in dengue episodes and estimated annual percentage changes (EAPCs) of the age-standardized incidence rate (ASR) were calculated to quantify the temporal trends of dengue infection.

RESULTS

Globally, dengue ASR increased by 1.70% (95% CI 1.62%-1.78%) per year from 1990 to 2011; subsequently, it decreased by 0.41% (95% CI 0.20%-0.62%) per year from 2011 to 2019. However, the global number of dengue episodes increased steadily by 85.47% from 30.67 million in 1990 to 56.88 million in 2019. Against the global trend of decreasing ASR from 2011 to 2019, an increasing trend was reported in Oceania (EAPC 11.01, 95% CI 8.79-13.27), East Asia (EAPC 4.84, 95% CI 2.70-7.03) and Southeast Asia (EAPC 0.38, 95% CI 0.13-0.62). For socio-demographic index (SDI) regions, ASR continued to have an increasing trend in the middle (EAPC 0.26, 95% CI 0.07-0.45) and high-middle (EAPC 1.70, 95% CI 0.98-2.42) SDI regions from 2011 to 2019. In contrast to the global peak age of dengue incidence rate (10 to 25 years), the dengue incidence rate of older people (> 65 years) was higher than in other age groups in low and low-middle SDI regions. Additionally, the proportions of dengue episodes in the > 70-year-old age group increased in 2019 (using the baseline in 1990 or 2011) in most GBD regions.

CONCLUSIONS

Global dengue episodes have increased tremendously in 3 decades. Although global dengue ASR decreased in the last decade, it is still increasing in hyperendemic regions including Oceania, East Asia and Southeast Asia, and also in the middle and high-middle SDI regions. More attention should be paid to the elderly because of the higher dengue incidence rate among them in low and low-middle SDI regions and the increased proportions of dengue episodes among the elderly in most GBD regions. Therefore, more efforts should be undertaken to develop targeted prevention strategies for crucial regions and older populations.

Emerging Mosquito-Borne Viruses Linked to Aedes aegypti and Aedes albopictus: Global Status and Preventive Strategies

Emerging mosquito-borne viruses continue to cause serious health problems and economic burden among billions of people living in and near the tropical belt of the world. The highly invasive mosquito species Aedes aegypti and Aedes albopictus have successively invaded and expanded their presence as key vectors of Chikungunya virus, dengue virus, yellow fever virus, and Zika virus, and that has consecutively led to frequent outbreaks of the corresponding viral diseases. Of note, these two mosquito species have gradually adapted to the changing weather and environmental conditions leading to a shift in the epidemiology of the viral diseases, and facilitated their establishment in new ecozones inhabited by immunologically naive human populations. Many abilities of Ae. aegypti and Ae. albopictus, as vectors of significant arbovirus pathogens, may affect the infection and transmission rates after a bloodmeal, and may influence the vector competence for either virus. We highlight that many collaborating risk factors, for example, the global transportation systems may result in sporadic and more local outbreaks caused by mosquito-borne viruses related to Ae. aegypti and/or Ae. albopictus. Those local outbreaks could in synergy grow and produce larger epidemics with pandemic characters. There is an urgent need for improved surveillance of vector populations, human cases, and reliable prediction models. In summary, we recommend new and innovative strategies for the prevention of these types of infections.