MODELING THE IMPACT OF VARIABLE CLIMATIC FACTORS ON THE RISK OF WEST NILE VIRUS IN ILLINOIS
Kenneth E. Kunkel, ISWS, Champaign, IL; and R. Novak, R. Lampman, M. A. Palecki, and W. Gu
The basis for a climate index reflecting the risk of West Nile Virus (WNV) transmission is explored using a unique mosquito population data set for east-central Illinois. This data set consists of time series over 13 seasons of the relative proportion of Culex restuans Theobald and Culex pipiens L. The seasonal pattern of WNV transmission, like many flaviviruses, demonstrates a late summer to early fall peak in activity based on human and veterinary cases, as well as infected vectors and avian hosts. This pattern parallels the seasonal abundance of Cx. pipiens, which is dominant late in the warm season and, despite its predilection for birds, will feed on mammals and humans. In contrast, Cx. restuans is an early season ornithophagic species that may play a critical role in initiating transmission cyles in early spring and summer. The time of change in relative proportions from Cx. restuans to Cx. pipiens (crossover) is highly variable from year to year. Investigation of several thermal measures indicated that this variation could be related in large part to climate conditions with warmer (cooler) temperatures correlated with earlier (later) crossover dates. Models based on degree days and number of days of daily maximum temperature exceedance explained more than 60% of the variance while models based on minimum temperature exceedance explained no more than 52% of the variance. The models developed here to estimate crossover date from climate data provide one component of an overall climate index for the risk of WNV transmission.
Session 4, Air Quality, Health and Urban Climatology
Tuesday, 21 June 2005, 2:15 PM-5:00 PM, South Ballroom
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