In the study, published on 12 October in The American Journal of Tropical Medicine and Hygiene, two researchers analysed more than 2,000 genetic sequences of dengue viruses collected in the southeastern Chinese province of Guangdong, using data from GenBank, a US collection of publicly available DNA. Their results, the study says, indicate that the dengue 1 strain is native to the province.
“Based on data we have, it shows dengue is very likely endemic in China.”
Rubing Chen, University of Texas
The sample’s “surprisingly large” genetic diversity, combined with Guangdong’s role as an Asian commercial hub, makes the province a potential source of future dengue epidemics, the study adds.
“Based on data we have, it shows dengue is very likely endemic in China,” Rubing Chen, the study’s lead author and a pathologist at the University of Texas Medical Branch in the United States, tells SciDev.Net.
Maia Rabaa, a molecular epidemiologist at the Oxford University Clinical Research Unit in Ho Chi Minh City, Vietnam, says the study highlights dengue’s potential to invade and spread in previously non-endemic areas if conditions such as the size of mosquito populations, temperature and humidity variables and dense human populations are met.
A similar dengue trend had been observed in Florida, United States, and northern Vietnam, Rabaa says. She says the study should encourage public health officials in southern China to control mosquito populations and identify potential transmission hotspots.
Chen agrees that controlling mosquitoes is crucial to dengue eradication, but that doing so in a city such as Guangzhou, Guangdong’s provincial capital, will be difficult because it is so populous and crowded. “People [in the city] joke that two people in different buildings can shake hands,” she says.
Dengue fever infects as many as 390 million people worldwide every year. After lying relatively dormant in China for two decades, dengue returned in 2014, infecting more than 40,000 people in Guangdong within two months, the study says.
Duane Gubler, an infectious disease specialist at the Duke-NUS Graduate Medical School in Singapore, says the study would have been better if it had focused on a less naturally diverse characteristic, such as certain types of protein, to ensure that the strain really is endemic to the region. “We have known for years that there is tremendous genetic diversity in these viruses, within an individual patient, a mosquito, a single epidemic, a country and a region,” Gubler says. “The suggestion that dengue 1 might be endemic in Guangdong province is important, but they need more than sequence data to prove that.”
Chen acknowledges there are still gaps in the DNA sequences, which makes it harder to explain certain aspects of dengue infections in Guangdong. But she says her study analysed a more comprehensive batch of DNA sequences than previous studies had.