Dry weather induces outbreaks of human West Nile virus infectionsGuiming Wang, Richard B. Minnis, Jerrold L. Belant, & Charles L. Wax

What is West Nile virus?• WNV is a disease transmitted by mosquitoes.

• Symptoms range from mild to severe and include:• Abdominal pain• Diarrhea• Fever• Headache• Lack of appetite• Muscle aches• Nausea• Rash• Sore throat• Swollen lymph nodes• Vomiting

What is West Nile virus? • More severe forms of the disease can result in neuroinvasive

diseases, such as encephalitis.• Confusion• Loss of consciousness• Muscle weakness• Stiff neck• Weakness of one arm or leg

• In the most severe cases, WNV can even result in DEATH.

Where did West Nile virus come from?• WNV originated in Uganda in 1937.

• It wasn’t a problem in North America until 1999, when NYC had its first outbreak.

• Since then, WNV has spread rapidly across North America and has become a major public health concern in this region.

What was the purpose of the research study?

• Wang, et al. wanted to see whether or not dry weather in one year would induce outbreaks of human WNV the following year.

How did they conduct their research?• Wang and his colleagues used a Bayesian hierarchical model to

test their hypothesis.

• They collected information about the 193 human cases of WNV that were reported in 50 of the 82 counties in Mississippi in 2002.

• They also collected information about the total annual precipitation recorded at weather stations in 73 of the 82 Mississippi counties in 2001.

• They interpolated annual precipitation for the other 9 counties, which did not have their own weather stations, from the data they already had.

What did the researchers find?• Annual precipitation varied across the state of Mississippi in

2001, ranging from 111.9 cm to 208.1 cm.

• Central and western Mississippi received less precipitation than northern Mississippi.

• There was also considerable spatial variation across Mississippi, with the greatest risk of human WNV in west central Mississippi during 2002.

What can we conclude from these results?• The areas that received less precipitation in one year had

greater risk of incidences of WNV for the following year.• This confirms the original hypothesis.

• As the magnitude and frequency of droughts are predicted to increase from global warming, the results suggest the risk of human WNV will also increase.

• Further research is necessary to better understand the reasons for this.

Additional Information• Wang, G., Minnis, R.B., Belant, J.L., & Wax, C.L. (2010). Dry

weather induces outbreaks of human West Nile virus infections. BMC INFECTIOUS DISEASES, Volume 10, Article 38.

• PubMed Health (2010). West Nile virus. Retrieved from http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004457/

• Amy, J. (2012). Fifth West Nile virus death reported in Mississippi, two new cases in Hancock County (updated). Retrieved on October 1, 2012 from http://blog.gulflive.com/mississippi-press-news/2012/10/fifth_west_nile_virus_death_re.html