Abstract
BackgroundDengue virus remains a major threat in Vietnam, while chikungunya virus is expected to become one. Surveillance was conducted from 2012 to 2014 in Vietnam to assess the presence of dengue and chikungunya viruses in patients hospitalized with acute fever in five Vietnam provinces neighboring Lao PDR and Cambodia. Surveillance was extended to mosquitoes present in the vicinity of the patients’ households.ResultsA total 558 human serum samples were collected along with 1104 adult mosquitoes and 12,041 larvae from 2250 households. Dengue virus was found in 17 (3%) human serum samples and in 9 (0.8%) adult mosquitoes. Chikungunya virus was detected in 2 adult mosquitoes (0.18%) while no chikungunya virus was detected in humans. Differing densities of mosquito populations were found, with the highest in the Long An Province border with Cambodia. Long An Province also displayed the lowest rate of infection, despite a very high Breteau Index, high human population density and presence of the main cross border road system. The highest incidence was found in Dac Nong Province, where the Breteau and Container indices were the second lowest. Dengue virus was detected in five Aedes albopictus, three Aedes aegypti and one Culex vishnui. Chikungunya virus was detected in two Ae. aegypti. All infected mosquitoes belonged to haplotypes described in other parts of the world and a number of novel haplotypes were found among uninfected mosquitoes.ConclusionsDengue is considered to be regularly introduced to Vietnam from Cambodia, mostly through human movement. The data reported here provides a complementary picture. Due to intensive international trade, long-distance transportation of mosquito populations may play a role in the regular importation of dengue in Vietnam through Ho Chi Minh City. It is important to decipher the movement of mosquitoes in Vietnam, not only at the Lao PDR and Cambodia borders but also through international trade routes. Mosquito surveillance programs should address and follow mosquito populations instead of mosquito species.
Highlights
The current expansion of arbovirus diseases is largely due to mosquito vector range extension, driven by climate change, the globalization of transport, and to increased human movement
Dengue is considered to be regularly introduced in Vietnam from neighboring countries, i.e. Cambodia and Lao Lao People Democratic Republic (PDR), and recently, dengue was shown to initiate in Ho Chi Minh City and to expand north by successive waves [13]
Patient cohort A total of 558 serum samples were collected from patients presenting with acute fever and symptoms compatible to Dengue virus (DENV)/Chikungunya virus (CHIKV) infection admitted during the 2012–2014 period in the five preventive medicine centers selected
Summary
The current expansion of arbovirus diseases is largely due to mosquito vector range extension, driven by climate change, the globalization of transport, and to increased human movement. Aedes-borne viruses, such as dengue and chikungunya virus, are targeted by national surveillance programs. Over the past 50 years dengue has spread inexorably from 9 countries prior to 1970 to over 124 today, with an increase of incidence multiplied by 30 [2]. Dengue remains a major health problem in Vietnam and the number of cases has increased over the past 15 years [5]. Dengue virus remains a major threat in Vietnam, while chikungunya virus is expected to become one. Surveillance was conducted from 2012 to 2014 in Vietnam to assess the presence of dengue and chikungunya viruses in patients hospitalized with acute fever in five Vietnam provinces neighboring Lao PDR and Cambodia. Surveillance was extended to mosquitoes present in the vicinity of the patients’ households
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