Reported illnesses from mosquito, tick, and flea bites have more than tripled in the U.S., with more than 640,000 cases reported during the 13 years from 2004 through 2016, according to the Centers for Disease Control and Prevention.
Among mosquito-borne diseases, the most common illness is caused by West Nile virus, a pathogen carried by birds. Culex mosquitos feed on birds and then infect hundreds of thousands of Americans each year with their bite. Most people don’t get sick, but a small number get very sick, with symptoms include brain inflammation that can lead to death. To see the latest West Nile data (as of January 2019), look at this CDC map. For more historical data and see how West Nile has expanded, look at this CDC page. For a CDC Morbidity and Mortality Weekly Report with additional West Nile and vector-borne disease data, see here.For data on diseases caused by other mosquitos and ticks, see this CDC map. While Zika (a virus carried by mosquitos that can cause fetal anomalies and death) has diminished as a threat in the continental U.S., it remains a risk in U.S. territories and other countries. For a map of Zika cases, see this CDC map. For Zika travel information, see this CDC map.