Background: Transmission of WNV to humans in the United States typically occurs between June and September since warm temperatures accelerate mosquito life cycle. Precipitation can cause increase in aquatic breeding but outbreaks often depends upon human water management. We examine epidemiology, patterns of WNV disease transmission,and identification of high-risk areas in the United States from 2003 to 2014.
Methods: Trends and relationships of WNV cases and climatic factors were analyzed among the regions of the United States from 2003 to 2014. Human WNV tabulate data and climatic data were obtained from Centers for Disease Control, and NOAA and Climate Data Guide respectively. Canonical correspondence analysis (CCA) was performed using variables: (i) neuroinvasive disease cases, non‐neuroinvasive disease cases, deaths, presumptiveviremic blood donors,(ii) precipitation, temperature, Palmer Drought Severity Index (PDSI) and population density. The CCA ordination was explained the variability between WNV disease cases andclimatic variables. Biplots were used to visualize the associations between WNV cases and climatic anomalies.
Results: We compared the state wise WNV disease cases in relation to climatic and population density in the United States from 2003 to 2014. A total of 4064 cases in 2006, 956 cases in 2010 and, 2141 cases in 2014 were reported in the 32 states of the US. Colorado state reported the highest WNV cases in 2003 (2947 cases; 33%), followed by Texas in 2012 (1868 cases; 35%) and California in 2014 (801 case; 37%). CCA ordination showed distinguishable clustering patterns between south central (Texas, Louisiana, Mississippi, Arkansas, and Oklahoma) and northern Great Plains (North Dakota, South Dakota, and Nebraska) regions (Fig. 1). High temperature and prolong drought were the most important variable predictor for high WNV outbreak.
Conclusion: Vector control methods focusing on prevention must be implemented to avoid epidemics of WNV if high temperature is leading to an unusual drought especially at the risk areas,such as Texas and California. However, high temperature with moist spell anomalies in the south central region showed a negative influence on WNV outbreak.
R. Varot Kangath,
J. Souza Borges, None
R. Ramachandrapai, None