Associations between meteorological variables, vector indices and dengue hospitalizations in Can Tho, Vietnam: a field survey

Abstract

18 19 42The house-(HI), container-(CI), Breteau (BI), and pupal (PI) indices were associated with relative 43 humidity (1-month lag, IRR HI =1.10 (95% CI 1.06, 1.13) per 1% increase), IRR CI =1.10 (95% CI 1.02, 44 1.19), IRR BI =1.17 (95% CI 1.14, 1.21), IRR PI =1.12 (95% CI 1.10, 1.14)). Vector indices were also 45 associated with precipitation (1-month lag) and to a lesser degree, hours of sun and mean 46 temperature. Ae. aegypti larval density was associated with not cleaning water storage containers 47 (RR=2.50, 95% CI 1.59, 3.66), not having access to municipal waste pick-up (RR=3.15, 95% 48 CI2.09, 4.75), disheveled clothes in the home (RR=1.85, 95% CI 1.24, 2.74) and season (RR[rainy 49 season]=3.10, 95% CI 2.18-4.48). The most productive containers were water storage containers 50 (relative pupal productivity 87%). Dengue hospitalization rates were associated with relative 51 humidity (2-month lag, IRR=1.11 (95% CI 1.06, 1.17) per 1% increase). Only the PI (1-month lag)52 was significantly associated with dengue hospitalization rates (IRR 1.04, 95% CI 1.00, 1.07). 53Mosquito avoidance behaviors were more frequent in the dry season (92.5% vs. 86.0% of 54 interviewees endorsed one or more forms of mosquito prevention, p<0.001). There was also less 55 use of larval elimination strategies (39.2% vs. 50.5%, p<0.001) during the rainy versus the dry 56 season. 57 58 Conclusion 59 Our study reveals a strong effect of relative humidity on vector indices and dengue hospitalization 60 rates. This may be due to the mosquito's vulnerability to desiccation, and the association warrants 61 further study. Our findings also demonstrate, however, that during the rainy season when mosquito 62 prevention is most needed, the use of fans, repellant coils and maintenance of water storage 63 containers is actually reduced. Water storage containers were by far the most productive of pupae, 64 and should be targeted in vector control activities. 65 66 4 67 68 69 Author summary 70 71 Climate plays an important role in the geographic distribution and burden of disease due to dengue, 72 owing to the vector and virus' sensitivity to temperature, humidity, and rainfall. In the Mekong Delta 73 in Vietnam, where dengue poses a significant health burden, average temperatures have increased 74 by 0.5°C since 1980. To better understand the influence of climate on dengue, this study examines 75 its influence on dengue hospitalization rates, vector breeding behavior and human mosquito 76 avoidance behaviors. We sampled 400 households every 2 months for one year for the presence of 77 the dengue vector, Aedes aegypti, and the productivity of different types of household containers. 78Human mosquito avoidance behaviors, such as the use of fans, mosquito repellant, and larval 79 elimination strategies were also recorded. The association between dengue hospitalizations, mean 80 temperature, relative humidity, precipitation, and the number of hours of sun were established, and 81 risk factors for the abundance of Ae. aegypti larvae were determined...

Impact of Climate Change on Human Infectious Diseases: Dengue

“…This is because at low temperatures they prevent the development of the Aedes aegypti mosquito [43]. In Can Tho (Mekong, Vietnam), [56] founded that the relative humidity was the most important meteorological predictor for dengue hospitalizations.…”

Ambient Temperature Effects on Hospitalization Risk Among Farmers

“…Previous studies in Vietnam have reported the effect of increased temperatures on the risk of hospital admission in general populations, 35,36 in specific age groups, 37 and in specific diseases. [38][39][40] However, to the best of the author's knowledge, there is no evidence of the heat effect on hospital admission risk among farmers in Vietnam. Therefore, this study aims to assess the effect of high temperatures on hospitalization risk for all causes and heat-sensitive diseases among Vietnamese farmers.…”