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

itoggle caption Justin Sullivan/Getty Images

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

itoggle caption Mario Tama/Getty Images

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

itoggle caption iStockphoto.com

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

itoggle caption LM Otero/AP

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

itoggle caption Gerry Broome/AP

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 TuneInToHepC.com hide caption

itoggle caption Rob Bennett/AP Images for TuneInToHepC.com

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

itoggle caption Lenny Ignelzi/AP