AsianScientist (Oct. 27, 2015) – Dengue is often associated with Southeast Asia, the Americas and other tropical climes. China is not necessarily the first place that springs to mind when one thinks of dengue. However, a new genomic study published in the American Journal of Tropical Medicine and Hygiene, has revealed that dengue could become endemic to Southern China.
Dr. Chen Rubing, main investigator on the study at the University of Texas Medical Branch, and her colleague Dr. Han Guan-Zhu, evaluated all dengue virus sequences (approximately 10,000 in total) from China from a public database. A striking number of individual variants of the virus were found: 50 individual variants of DENV-1 in China, 20 variants of DENV-2, and lower numbers of DENV-3 and DENV-3. Multiple variants of DENV-1 and DENV-2 were found also during the 2014 Guangdong outbreak, where 40,000 people were affected.
The results of this paper show that there is a complex and diverse mix of viral subtypes in China, highlighting two key points: that it is quite likely that dengue has already become endemic to southern China, and that there is a higher risk of epidemic dengue in future. It has been unclear so far as to whether dengue persists in between disease outbreaks in China. This study shows that dengue can, indeed, persist year round.
In China, dengue is often thought to be an ‘imported’ disease. One such incident occurred in 2014 when eight out of a group of 28 men who had traveled to Singapore and Indonesia contracted dengue fever. While global transmission has made disease control more complex, this study suggests that dengue disease dynamics in southern China may not always be as straightforward as an isolated, imported incident.
Several key factors have catalyzed the spread of the disease throughout the globe via the main mosquito vector, Aedes aegypti. These include rural-urban migration, inadequate basic urban infrastructure such as an unreliable water supply and improper water storage, and increase in volume of solid waste such as plastic containers that allow easy breeding of mosquitoes.
Prevention is imperative in combating dengue. As it stands, according to the World Health Organization (WHO), dengue fever affects 50 million annually, causing 22,000 deaths. With the impending El-Niño phenomenon, dengue cases are slated to rise in dengue endemic countries.
To curb transmission, the Chinese Center for Disease Control and Prevention in Guangdong has adopted novel techniques. By introducing genetically modified mosquitoes that have reproductive advantage but are not able to carry the virus, the number of mosquitoes with the virus will decrease.
As for vaccines, Chen is hopeful for a dengue vaccine, but acknowledges that this is a complex process. Dengue can still affect a person who is vaccinated against one subtype of the dengue virus, and the symptoms will be even more severe. This is where Chen’s study factors into dengue prevention, as genomic analysis can be used to track different strains of dengue across regions, and will be vital to establish potential vaccine candidates. With the world getting smaller, the dengue virus respects no borders.
The article can be found at: Chen et al. (2015) Dengue in China: Comprehensive Phylogenetic Evaluation Reveals Evidence of Endemicity and Complex Genetic Diversity.
———
Source: Asian Scientist Magazine; Photo: Agência Brasília/Flickr/CC.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
