News that Anthony Fauci, long-time former head of the National Institute of Allergy and Infectious Diseases, is recovering from a bad bout of West Nile virus fever throws a spotlight on a disease that sickens plenty of Americans every summer, but which gets little attention.
Transmitted by mosquitoes, the virus causes symptom-free infections in most people who contract it. But about one in five people infected will develop symptoms, and a portion of them will become quite ill, as did Fauci, who is 83. He was hospitalized for six days, and told STAT in an interview that he is now recovering and “absolutely going in the right direction.”
Here are some facts about West Nile virus infection.
Its history: West Nile virus was first detected in the United States in 1999, when a number of human cases were diagnosed in New York State. The virus is believed to have come into the country either in mosquitoes that hitched a ride on airplanes, or in the blood of infected people. The virus was previously detected only in Africa, the Middle East, Asia and parts of Europe. Since it arrived in North America, it has spread across much of the continent.
Its lifecycle: The virus is transmitted to humans by infected mosquitoes, primarily Culex mosquitoes. Infected mosquitoes bite birds and horses, which become viremic — they have the virus in their blood — and can infect more mosquitoes that feed off them. Over the course of the summer months, that cycle leads to an amplification of the population of infected mosquitoes, raising the risk that infected mosquitoes will feed off and infect people. Most human infections occur in the latter part of the summer, peaking in August and September. The number of human infections varies from year to year.
https://www.cdc.gov/west-nile-virus/data-maps/historic-data.html
The illness it triggers: The Centers for Disease Control and Prevention estimates that about eight of 10 people infected don’t develop symptoms. The risk of becoming sick with WNV after infection rises with age, with people 60 and older at higher risk, as well as people with cancer, diabetes, hypertension, kidney disease, and organ transplant recipients. About one in five people become sick; symptoms include fever, chills, muscle and joint aches, headaches, vomiting and diarrhea, and rash. About one in 150 people develop neurological symptoms, when the virus moves into their central nervous systems. And about one in 10 people who develop severe illness die from the infection.
How it’s prevented and how it’s treated: There is no West Nile vaccine, so the best way to prevent infection is to take steps to avoid mosquito bites. Get rid of standing water around your home; mosquitoes lay eggs in water. Use DEET-containing mosquito repellant. There is no WNV-specific antiviral treatment. When people become seriously ill, they may need to be hospitalized and treated with supportive care, such as intravenous fluids and pain medication.
The numbers: Figures do not represent the full infection picture, because most people who contract this virus will never be tested for it. Some years are worse than others in terms of the burden of WNV infections. For instance, there were nearly 10,000 detected cases in 2003, the worst year on record in the U.S., according to CDC data. Last year there were nearly 2,600 reported cases. The CDC says that as of Aug. 20, it has been advised of 216 WNV infections, in 33 states so far this year. Of those cases, 142 involved neuroinvasive disease, the most serious form of WNV fever.
Source: CDC
https://www.cdc.gov/west-nile-virus/data-maps/historic-data.html