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Summertime, for most of the country, means warmer temperatures, spending more time outside dealing with mosquitos that may or may not be infected with the West Nile Virus.
Last year in Texas, Dallas County had one of the largest reported outbreaks in the country; 398 cases of West Nile Virus illness.
"Part of the challenge of West Nile is that it's very unpredictable in causing very focal and intense outbreaks throughout the United States," said Dr. Wendy Chung with Dallas County Health and Human Services.
She and co-authors examined particular features of the 2012 outbreak including weather patterns, timing and geographic distribution of human cases and also mosquito infection.
Researchers analyzed 11 years of historical human case and mosquito surveillance data from 12 local counties.
"Our outbreak years in 2012 and 2006 were associated with a lack of winter freezes, so lack of temperatures below 28 degrees Fahrenheit," said Dr. Chung.
The study appears in JAMA, Journal of the American Medical Association.
"There were certain what we call geographic hot spots, the same geographic areas within our county tended to be affected more heavily during an outbreak," said Dr. Chung.
Researchers say the data emphasize that strong mosquito surveillance is the most important action that can be taken by public health departments nationwide.
Knowing where the mosquitos are and how many are infected is critical.
"This provides potentially one to two weeks of lead time for health departments to deliver maximally effective vector control measures in a timely manner in order to prevent the most number of cases," said Dr. Chung.