Fauci, the now 83-year-old who led the country through the COVID-19 pandemic as the former director of the National Institute of Allergy and Infectious Diseases, was hospitalized nearly two weeks ago, according to CBS News chief medical correspondent Dr. Jonathan LaPook, who posted to X that he spoke with Fauci over the phone this weekend. 

The infectious disease doctor was hospitalized after “developing fever, chills, and severe fatigue,” LaPook shared. “Evaluation revealed that he had been infected with the West Nile virus, likely from a mosquito bite that he got in his backyard.”

What is West Nile virus? 

West Nile virus was first detected in the 1930s in the West Nile subregion of Uganda and is now the leading cause of mosquito-borne disease worldwide. It has infected over 2,500 this year in the U.S. alone and, according to the U.S. Centers for Disease Control and Prevention (CDC), it’s most commonly spread through a bite from an infected mosquito. 

But symptoms of West Nile virus—which could strike anyone, especially during peak mosquito season in the summer and early fall—do not show at all in 70% to 80% of people who are infected, according to the CDC. In fact, just over 50,000 symptomatic cases have been detected in the U.S. since 1999.  

People at risk for developing symptoms, including fever, headache, body aches, vomiting, diarrhea, and rashes, include those over 60 and individuals with cancer, diabetes, high blood pressure, kidney disease, or a recipient of an organ transplant (where, in rare cases, the disease can spread from the donor to the recipient), according to the Cleveland Clinic. 

Mild symptoms can be treated at home with typical over-the-counter medications. 

Who is most at risk for more severe illness?

While symptoms, when they do show, typically subside and lead to complete recovery within about a week, others, especially immunocompromised individuals, may feel sick for longer—up to 14 days. Pregnant people are also at higher risk, as they can spread the disease to their fetus, although it’s very rare. “Most women known to have been infected with WNV during pregnancy have delivered infants without evidence of infection or clinical abnormalities,” according to the CDC. 

But hospitalization is common if someone has a high fever, intense headache, fatigue, and chills, as with Fauci. If other neurological symptoms persist, hospitalization may be required to receive IV fluids or ventilation. 

In the most severe cases, people with West Nile virus can develop encephalitis and meningitis, neurological conditions that cause brain and spinal cord inflammation. Symptoms include seizures, muscle weakness, confusion, and paralysis. For those with severe cases, there is a 10% chance of death. 

What’s the best way to prevent West Nile virus?

There is no official treatment for the West Nile virus other than a prophylactic approach: to protect yourself from mosquito bites in the first place. Using insect repellent and wearing protective clothing can help minimize the risk of bites. 

More broadly, the CDC pushes for “community-level mosquito control programs to reduce vector densities” through spraying and monitoring. 

As for Fauci, LaPook shared, “he left the hospital three days ago and is recovering at home. The prognosis is for a full recovery.”