Download Dry weather induces outbreaks of human West Nile virus infections

Dry weather induces
outbreaks of human West
Nile virus infections
Guiming 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:
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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.
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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-pressnews/2012/10/fifth_west_nile_virus_death_re.html