West Nile Virus Cases 40% Higher Than Normal

West Nile virus reigns as the leading cause of mosquito-borne illness in the continental U.S., and this year is expected to be a higher-than-average year. As of Sept. 30, the Centers for Disease Control and Prevention (CDC) has confirmed 1,324 cases across 42 states, including 874 neuroinvasive cases—the severe form of the disease that affects the brain and central nervous system. Colorado overwhelmingly leads the U.S. case count with more than 241 reported cases as of Sept. 30.

This year’s case count is already 40% higher than typical seasons, and last year the CDC reported 1,791 cases. Experts point to a warming climate as a factor in increased mosquito activity, which usually runs through October.

Despite growing cases, only 15% of Americans are worried about contracting West Nile virus or dengue fever in the next three months, according to a recent Annenberg Public Policy Center (APPC) of the University of Pennsylvania survey conducted Aug. 5 to 18. This figure is unchanged from last year, reflecting a persistent disconnect between risk and public perception, researchers said. For infection preventionists (IPs), the data underscores the ongoing need for clear and practical messaging and surveillance regarding vector-borne disease prevention, Infection Control Today reported.

While most people infected with the virus do not develop symptoms, it does cause symptoms in some people, ranging from a mild, flu-like illness to a more severe illness affecting the central nervous system—which can ultimately result in hospitalization and death.

The APPC health survey also found:

• Most people (75%) know that one can get West Nile or dengue fever from being bitten by an infected mosquito and the best defense against these diseases is to avoid getting bitten (81%).
• Nearly one in five people (19%) incorrectly said that scientists think an infected person coughing or sneezing on someone is a means of West Nile transmission. About four in 10 (39%) said they are unsure how it is transmitted. 
• Nearly half (48%) are not sure what the symptoms of West Nile virus are.
• Just 14% know not to put insect repellent under your clothing, and 33% know to first apply sunscreen, let it dry, and then put on insect repellent.
• Currently no antiviral treatment exists for West Nile virus or dengue, but only a fifth of adults (22%) know this. Most are either unsure (61%) or believe an antiviral treatment (17%) is available.