Dr. Anthony Fauci, the former director of the National Institute of Allergy and Infectious Diseases, was hospitalized with a case of West Nile virus but is now recovering at home.

West Nile Virus is a relatively rare and potentially deadly disease, which is primarily spread by mosquitos. It can cause fever, headache, body aches, vomiting, diarrhea or rash, the U.S. Centers for Disease Control and Prevention says.

Jenn Kuzmuk, a spokesperson for Fauci, confirmed his illness to USA TODAY on Saturday and said Fauci is expected to make a full recovery.

Fauci, 83, was in the hospital for six days, the Washington Post reported.

Fauci became a household name during the COVID-19 pandemic as a top public health expert. For some, he has since has become a focus of anger and frustration for his stands on vaccination, science and social distancing – the same qualities that make him highly admired by others.

Most people who contract West Nile Virus never develop symptoms, the CDC said. About one-in-five have a fever or other symptoms, while about one in 150 infected develop serious illness that can sometimes be fatal.

The virus is endemic in the U.S. Exactly 25 years ago, in August 1999, officials identified West Nile as being introduced to the country, first in New York City.

Cases of West Nile are highest in the U.S. during the summer through fall, when mosquitoes are most active. Annual cases in the U.S. fluctuate widely, the CDC says, but this year there have been 216 cases in 33 states identified as of Aug. 20. Of those cases, 142 were neuroinvasive, meaning it affects the nervous system and can lead to meningitis or encephalitis.

There are no vaccines to prevent West Nile or medications to treat it.

Contributing: Elizabeth Weise