2012 West Nile Virus Outbreak: How Deadly Is It?

Scientists sort mosquitoes gathered in the field by species and by sex, since only females bite humans. The bugs are ground up so that they can be tested for the virus, telling researchers how fast it is spreading, and where pesticides should be used and whether or not they are working.

When used correctly, the pesticides are highly effective at killing off mosquitoes. But aerial spraying in cities such as Dallas has led to a backlash from residents who worry that the spraying may be dangerous.

Dr. Lyle Petersen, the director of the CDC’s Division of Vector Borne Illnesses, is the man leading the government’s battle against West Nile and maintains that spraying is safe.

“The EPA has looked at all of this, and has deemed these pesticides as being safe,” Peterson said.