What to know about West Nile virus, the illness that sickened Dr. Anthony Fauci

(CNN) — When Dr. Anthony Fauci became infected with West Nile virus, a mosquito-borne disease, it was so severe that he had to be hospitalized.

Fauci, once the top US infectious disease expert, is now recovering at home —although he told Stat , the health and medical news website, that it could take “weeks and weeks to get back to normal.”

With summer temperatures persisting, I wanted to know more about West Nile — what are the symptoms and what makes it so serious? Are there vaccines and treatments available? And, as the summer’s high temperatures and peak mosquito season continues, what can we do to reduce our risk of contracting this and other mosquito-borne illnesses?

To help with these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner.

CNN: What are the symptoms of West Nile virus disease and how serious is it?

Dr. Leana Wen: West Nile virus is the No. 1 cause of mosquito-borne disease in the continental US, according to the US Centers for Disease Control and Prevention . It is most commonly spread through the bite of an infected mosquito. The time of the year when this disease is most often seen is the summer and early fall.

Most people infected with West Nile virus are asymptomatic. Of those who develop symptoms, many have flu-like symptoms such as fever, headaches, body aches, swollen lymph nodes and nausea.

There is a subset of people who develop a neurological form of the disease. (Fauci said he did not.) These cases can involve brain inflammation and swelling resulting in confusion, seizures, paralysis, coma and death. Individuals can also experience long-term neurological consequences as a result of contracting West Nile.

CNN: How common is West Nile?

Wen: In the US this year, the CDC has documented 33 states that have had West Nile cases. In 2023, 47 states reported West Nile cases; in total, there were more than 2,400 reported instances , though this was likely a significant undercount given the number of asymptomatic and mildly symptomatic cases.

The West Nile virus is also found throughout the world , including across Africa, Europe, Asia and the Middle East.

CNN: Can West Nile be spread from person-to-person?

Wen: West Nile cannot be transmitted through casual contact with other humans who have the disease. Humans are also believed to be “dead-end hosts,” meaning that a mosquito that bites an infected human is not going to transmit the virus to another human.

However, there have been documented cases of transmission through blood transfusion, organ transplantation and, rarely, from mother to baby during pregnancy and breastfeeding. The dominant mode of transmission, by far, is through mosquito bites.

CNN: How is West Nile virus disease diagnosed? What should someone do if they think they have it?

Wen: There are blood tests that can detect antibodies to West Nile virus that are used for diagnosis. Patients with the neurological form of the illness may also receive a spinal tap, and testing could be done of the spinal fluid.

Individuals concerned about West Nile should speak with their health care provider to discuss whether and how they can pursue diagnostic testing.

CNN: Is there a vaccine or treatment for West Nile?

Wen: Unfortunately, there is no vaccine and no specific antiviral treatment for West Nile. Individuals diagnosed with it receive supportive treatment to address their symptoms, but there is no directed antiviral therapeutic at this time.

CNN: In addition to West Nile, are there other mosquito-borne diseases that people should be aware of?

Wen: Dengue is another example of a virus transmitted by mosquito. Most cases in the US are from travelers, but local transmission has also occurred. Those traveling to other parts of the world need to consider malaria, which could be deadly.

And there are rarer cases of mosquito-borne diseases that can be very serious. For instance, Eastern equine encephalitis , also called EEE, was recently reported in Massachusetts — a disease that has a mortality rate of about 30% .

CNN: As the summer and peak mosquito season continue, what can people do to reduce their risk of contracting mosquito-borne illnesses?

Wen: Prevention is key, especially as there is no specific vaccine or treatment for West Nile. People should take these steps between peak West Nile season, which is typically July to September, though cases have also been reported in the continental United States as early as June and as late as October.

First, reduce mosquito bites. Wear long-sleeve shirts and long pants when possible, especially when going out at sunrise, sundown and during the night, when mosquitoes are most active. Apply US Environmental Protection Agency-registered insect repellents to all areas of exposed skin. These will contain active ingredients like DEET. When used as directed, they are safe, including for children and pregnant women. An added step is to wear permethrin-treated clothing , which further reduces the risk of mosquito bites.

Second, work to reduce mosquitoes near you. Use screens on windows and doors, especially between dusk and dawn. Remove standing water in your garden and around your home, as these are key breeding grounds for mosquitoes. Look for items around your home that can hold water, like buckets, trash containers and toys, and empty and wash them at least once a week.

Third, assess your personal risk. If you are going to be traveling out of the country and going to areas known to have diseases such as yellow fever and malaria, make sure to ask your health care provider about additional prophylactic steps, such as the yellow fever vaccine and antimalarial pills.

Know, though, that there are risks close to home, too. Fauci said that he believes he got bitten by mosquitoes in his garden in suburban Washington, DC.

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