Climatic-driven seasonality of emerging dengue fever in Hanoi, Vietnam

Abstract

BackgroundDengue fever (DF) has been emerging in Hanoi over the last decade. Both DF epidemiology and climate in Hanoi are strongly seasonal. This study aims at characterizing the seasonality of DF in Hanoi and its links to climatic variables as DF incidence increases from year to year.MethodsClinical suspected cases of DF from the 14 central districts of Hanoi were obtained from the Ministry of Health over a 8-year period (2002–2009). Wavelet decompositions were used to characterize the main periodic cycles of DF and climatic variables as well as the mean phase angles of these cycles. Cross-wavelet spectra between DF and each climatic variables were also computed. DF reproductive ratio was calculated from Soper’s formula and smoothed to highlight both its long-term trend and seasonality.ResultsTemperature, rainfall, and vapor pressure show strong seasonality. DF and relative humidity show both strong seasonality and a sub-annual periodicity. DF reproductive ratio is increasing through time and displays two clear peaks per year, reflecting the sub-annual periodicity of DF incidence. Temperature, rainfall and vapor pressure lead DF incidence by a lag of 8–10 weeks, constant through time. Relative humidity leads DF by a constant lag of 18 weeks for the annual cycle and a lag decreasing from 14 to 5 weeks for the sub-annual cycle.ConclusionResults are interpreted in terms of mosquito population dynamics and immunological interactions between the different dengue serotypes in the human compartment. Given its important population size, its strong seasonality and its dengue emergence, Hanoi offers an ideal natural experiment to test hypotheses on dengue serotypes interactions, knowledge of prime importance for vaccine development.

Influenza and dengue virus co‐infection impairs monocyte recruitment to the lung, increases dengue virus titers, and exacerbates pneumonia

“…Here we establish a causal relationship between co‐infection and increased disease severity, as H1N1–DENV co‐infected mice succumbed to infection at otherwise sublethal virus doses. Consequently, co‐infection is a risk factor for severe disease in tropical regions, such as Brazil , Thailand, and Vietnam , where influenza and dengue viruses regularly co‐circulate.…”

“…Little information, however, exists regarding whether co‐infection of influenza with other acute viruses affect disease outcome. Seasonal influenza A virus and DENV epidemics regularly overlap in several regions, including Brazil , Thailand, and Vietnam . During the 2009 influenza H1N1 pandemic, additional countries, including Nicaragua , Puerto Rico , and India reported cases of co‐infection with DENV, resulting in severe disease .…”

Seasonality of Viral Encephalitis and Associated Environmental Risk Factors in Son La and Thai Binh Provinces in Vietnam from 2004 to 2013

“…37,38 In addition, seasonality of enteroviruses with peaks during summer has been described in Korea, Taiwan, and the United States. [39][40][41] The Taiwan study found that enterovirus infection was significantly associated with increasing temperature and humidity, which was consistent with our study.…”

Developmental stress in South African hominins: Comparison of recurrent enamel hypoplasias in Australopithecus africanus and Homo naledi

“…For example, both dengue and malaria show twice-yearly occurrence in Vietnam with only a single annual rainy peak. 51,52 Similarly, malaria recurs twice a year in southern China with only a single annual moisture cycle. 53,54 Such an explanation fails to explain the difference in duration of stress between the two assemblages reported here.…”