Epidemiology of dengue fever in Hanoi from 2002 to 2010 and its meteorological determinants

Abstract

BackgroundDengue fever (DF) is a growing public health problem in Vietnam. The disease burden in Vietnam has been increasing for decades. In Hanoi, in contrast to many other regions, extrinsic drivers such as weather have not been proved to be predictive of disease frequency, which limits the usefulness of such factors in an early warning system.AimsThe purpose of this research was to review the epidemiology of DF transmission and investigate the role of weather factors contributing to occurrence of DF cases.MethodsMonthly data from Hanoi (2002–2010) were used to test the proposed model. Descriptive time-series analysis was conducted. Stepwise multivariate linear regression analysis assuming a negative binomial distribution was established through several models. The predictors used were lags of 1–3 months previous observations of mean rainfall, mean temperature, DF cases, and their interactions.ResultsDescriptive analysis showed that DF occurred annually and seasonally with an increasing time trend in Hanoi. The annual low occurred from December to March followed by a gradual increase from April to July with a peak in September, October. The amplitude of the annual peak varied between years. Statistically significant relationships were estimated at lag 1–3 with rainfall, autocorrelation, and their interaction while temperature was estimated as influential at lag 3 only. For these relationships, the final model determined a correlation of 92% between predicted number of dengue cases and the observed dengue disease frequencies.ConclusionsAlthough the model performance was good, the findings suggest that other forces related to urbanization, density of population, globalization with increasing transport of people and goods, herd immunity, government vector control capacity, and changes in serotypes are also likely influencing the transmission of DF. Additional research taking into account all of these factors besides climatic factors is needed to help developing and developed countries find the right intervention for controlling DF epidemics, and to set up early warning systems with high sensitivity and specificity. Immediate action to control DF outbreak in Hanoi should include an information, communication, and education program that focuses on training Hanoi residents to more efficiently eliminate stagnant puddles and water containers after each rainfall to limit the vector population growth.

Impact of Climate Variability and Abundance of Mosquitoes on Dengue Transmission in Central Vietnam

“…Dengue transmission occurs mainly in the rainy season, which is during the second half of the year in Vietnam. In Hanoi, where more than 75 % of dengue cases in northern Vietnam occur, dengue fever transmission showed a seasonal pattern, with a gradual increase in incidence from April to August and a peak in September and October [38,62]. Southern Vietnam is known to be a hyperendemic area where dengue transmission occurs all year round [34,63] with a particularly high incidence from August to November [38].…”

Surveillance of dengue vectors using spatio-temporal Bayesian modeling

“…This variation suggests local microclimate effects not captured by the single meteorological station and can be attributed to the particular characteristics of each area (Table 1 ). Minh An and Rocklöv [ 22 ] evaluated the effect of the interaction between rain and temperature on the number of dengue cases in Hanoi, Vietnam. They showed rain occurrence and temperatures between 15 and 30 °C to correlate to an increase in the number of dengue cases.…”

Feasibility and willingness to pay for dengue vaccine in the threat of dengue fever outbreaks in Vietnam

“…The DF endemic, characterized by annual seasonal peaks and outbreaks, occurred every 4–10 years (1983, 1987, 1998, 2009 and 2017). 15 In the 1998 outbreak, ~240,000 cases were reported with 377 deaths; and in the 2009–2010 epidemic, more than 230,000 cases were infected (142 deaths). 15 , 16 In 1999, a National Dengue Control Program was established to implement DF control activities, primarily focusing on controlling the vector–human transmission.…”

“… 15 In the 1998 outbreak, ~240,000 cases were reported with 377 deaths; and in the 2009–2010 epidemic, more than 230,000 cases were infected (142 deaths). 15 , 16 In 1999, a National Dengue Control Program was established to implement DF control activities, primarily focusing on controlling the vector–human transmission. 17 However, despite significant efforts, in 2017, Vietnam again suffered a large-scale outbreak from July to December with more than 184,000 people infected (32 fatal cases).…”

“… 17 However, despite significant efforts, in 2017, Vietnam again suffered a large-scale outbreak from July to December with more than 184,000 people infected (32 fatal cases). 18 , 19 Climate change was supposed to greatly contribute to the occurrence of the outbreaks since they coincided with the increased activity of El Nino and La Nina phenomenon. 15 Thus, the dengue vaccine has been proposed as a favorable approach and is being prioritized in the national DF control strategies.…”