West Nile virus infections increase in the DMV

It's peak season for West Nile virus in the DMV and reported infections from the mosquito-borne illness are increasing.

Why it matters: Most infected humans are asymptomatic, but the virus can cause flu-like symptoms — especially for people over 60 — long-term complications, and in rare instances, death.

Driving the news: Anthony Fauci was hospitalized for several days with West Nile virus (WNV), and is recovering at home in NW D.C.

• The former director of the National Institute of Allergy and Infectious Diseases told CBS that he was likely bitten by a mosquito in his backyard.
• Maryland just reported their first human infection of the year. A Baltimore-area resident tested positive for the virus, health officials said this week.

Threat level: Higher than normal. "Weather, especially temperature, is a key factor that affects the transmission," Julia Murphy, a Virginia public health official, tells Axios. "We had a mild winter and also a very hot, dry summer.  This tends to create an environment that's favorable for WNV."

• Plus: Mosquito season is getting longer with climate change, which means more opportunity for infection. Murphy says the typical West Nile season is July through September, though Virginia recorded their first case early this year — in June.

The big picture: WNV is the most frequent mosquito-borne infection in the region and the U.S. Roughly one in five people who are infected develop a fever and other symptoms, according to the CDC , and 1 in 150 develop serious illness that impacts the central nervous system.

• So far this year, the CDC has recorded 289 human cases from 33 reporting states, and 195 cases of the neuroinvasive infection.

Reality check: Human infections in the DMV are historically low. So far this year, there are three cases each in Virginia and D.C., and one in Maryland.

Zoom in: Both states and the District conduct mosquito surveillance to monitor the presence of viruses in mosquito populations. Since the first case of WNV appeared in D.C. in 2002, mosquitos have been trapped and tested, from June through early fall.

• WNV in mosquito populations doesn't directly translate to human infections. Maryland , for example, has reported 128 cases of WNV in mosquito pools since July. D.C. has tracked 14.

Between the lines: To prevent bites, the CDC recommends using EPA-registered insect repellents, wearing long-sleeved clothing during dawn and dusk hours when mosquitoes are prevalent, and draining or treating standing water where mosquitoes breed once a week.

Zoom out: A rare but potentially deadly mosquito-borne virus, eastern equine encephalitis (EEE), has been recently reported in New England, including one fatality in New Hampshire.

• Like WNV, there are no vaccines or medications to treat EEE, but its fatality rate is much higher — roughly 30% of infected people die, according to the CDC, and many survivors suffer neurological problems.

But the threat level is very low in the DMV. There are no reported cases — Virginia has only recorded six human EEE cases since 1975, the last over a decade ago.

• "We have not seen evidence of EEE spreading to Virginia even in years when some other states have reported outbreaks," says Murphy, who adds it's an "uncommon" disease in the U.S.