Technicians with the Contra Costa County Mosquito and Vector Control District spray insecticide in Brentwood, Calif., last month. Workers fogged areas of the county that had an increase in the numbers of mosquitoes carrying the West Nile virus. Justin Sullivan/Getty Images hide caption

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A man stands in a fountain in Washington Square Park on July 18, in New York City. Temperatures were expected in the upper 90's during another heat wave in the city. Mario Tama/Getty Images hide caption

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Two men from northwestern Missouri became ill after tick bites infected them with a previously unknown virus. hide caption

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A Beechcraft airplane sprays insecticide over Dallas early Monday morning to curb the spread of West Nile virus. LM Otero/AP hide caption

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People wait in line at the Durham County Health Department for the H1N1 flu vaccination in Durham, N.C., in November 2009. Gerry Broome/AP hide caption

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Gregg Allman and Natalie Cole perform at the Tune In to Hep C benefit concert at the Beacon Theatre in New York on July 27, 2011. Both singers have battled chronic hepatitis C. Rob Bennett/AP Images for hide caption

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Dr. Paul J. Pockros, a liver specialist at Scripps Green Hospital in San Diego, talks with hepatitis C patient Loretta Roberts in Jan. 2011. Lenny Ignelzi/AP hide caption

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