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. 2009 Jul;117(7):1049-52.
doi: 10.1289/ehp.0800487. Epub 2009 Mar 16.

Infectious disease in a warming world: how weather influenced West Nile virus in the United States (2001-2005)

Jonathan E Soverow  1 , Gregory A Wellenius, David N Fisman, Murray A Mittleman
Affiliations

Infectious disease in a warming world: how weather influenced West Nile virus in the United States (2001-2005)

Jonathan E Soverow et al. Environ Health Perspect. 2009 Jul.

Abstract

Background: The effects of weather on West Nile virus (WNV) mosquito populations in the United States have been widely reported, but few studies assess their overall impact on transmission to humans.

Objectives: We investigated meteorologic conditions associated with reported human WNV cases in the United States.

Methods: We conducted a case-crossover study to assess 16,298 human WNV cases reported to the Centers for Disease Control and Prevention from 2001 to 2005. The primary outcome measures were the incidence rate ratio of disease occurrence associated with mean weekly maximum temperature, cumulative weekly temperature, mean weekly dew point temperature, cumulative weekly precipitation, and the presence of > or = 1 day of heavy rainfall (> or = 50 mm) during the month prior to symptom onset.

Results: Increasing weekly maximum temperature and weekly cumulative temperature were similarly and significantly associated with a 35-83% higher incidence of reported WNV infection over the next month. An increase in mean weekly dew point temperature was significantly associated with a 9-38% higher incidence over the subsequent 3 weeks. The presence of at least 1 day of heavy rainfall within a week was associated with a 29-66% higher incidence during the same week and over the subsequent 2 weeks. A 20-mm increase in cumulative weekly precipitation was significantly associated with a 4-8% increase in incidence of reported WNV infection over the subsequent 2 weeks.

Conclusions: Warmer temperatures, elevated humidity, and heavy precipitation increased the rate of human WNV infection in the United States independent of season and each others' effects.

Keywords: West Nile virus; case-crossover study; climate change; global warming; mosquito; vector-borne illness; weather.

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Figures

Figure 1
Figure 1
Number of human WNV cases by week (A) and by week for each year (B) in the study sample.
Figure 2
Figure 2
OR and 95% CIs of reported WNV infection for a 5°C increase in maximum temperature (A) or dew point temperature (B), for the presence of ≥ 1 day with > 50 mm rainfall (C), or for a 20-mm increase in cumulative weekly precipitation (D).
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References

    1. Allen J. A modified sine wave method for calculating degree-days. Environ Entomol. 1976;5:388–396.
    1. Campbell G, Marfin A, Lanciotti R, Gubler D. West Nile virus. Lancet Infect Dis. 2002;9:519–529. - PubMed
    1. CDC (Centers for Disease Control and Prevention) [[accessed 1 June 2007]];Neuroinvasive and Non-Neuroinvasive Domestic Arboviral Diseases; 2004 Case Definition. 2004 Available: http://www.cdc.gov/epo/dphsi/casedef/arboviral_current.htm.
    1. CDC (Centers for Disease Control and Prevention) [[accessed 9 January 2008]];West Nile Virus Activity in the United States. 2007 Available: http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount07_detaile....
    1. Defilippo C, Epstein P. [[accessed 2 February 2008]];West Nile Virus and Drought. 2001 Available: http://www.conservationmedicine.org/papers/wnvanddrought.pdf.

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