August 12, 2024
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West Nile Virus cases are on the rise. Here’s how to protect yourself
West Nile fever is the most common mosquito-borne disease in the U.S. Here’s what you need to know about the infection.
West Nile fever is contracted through mosquito bites, but if you’re unlucky, the infection can cause severe illness and even death.
West Nile virus is present throughout the United States. Nearly all cases occur between July and October, and the first human infections and deaths have already been reported this year. There is no need to panic, but it is a reason to take precautions against the virus.
“West Nile virus has become established in the United States,” says Gonzalo Vásquez-Prokopec, a disease ecologist at Emory University. “We have to live with it.”
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The virus was first identified in the United States in 1999. The deadliest year to date was 2003, when about 10,000 cases were reported. Since then, infection levels have waxed and waned, likely due to a variety of factors, including climatic factors and the species of birds that serve as hosts for the virus.
“Initially, 2002 and 2003 were really big years,” said Christy O. Murray, an infectious disease expert at Emory University. “We had a big outbreak in 2012, and I think we’re going to see another one at this point.”
It’s not yet clear whether 2024 will be a bad year for West Nile virus. As of Aug. 6, there have been 103 confirmed cases in 26 states this year. That’s fewer than the 421 cases reported from January to July of 2023, but this year’s numbers are preliminary and subject to reporting delays, making it hard to draw conclusions. “West Nile virus is hard to predict and tends to vary from year to year, so we don’t know what specifically this year will be like compared to other years,” says Erin Staples, a medical epidemiologist at the Centers for Disease Control and Prevention.
West Nile virus has killed just under 3,000 people in the United States since 1999, but experts warn of the risks of underestimating the virus. Most infected people are asymptomatic, but the virus causes fever in about 20% of people, and in a small percentage of cases (about 1 in 150), it becomes what doctors call “neuroinvasive,” reaching the brain and causing encephalitis, or the spinal cord and causing meningitis.
In either scenario, neuroinvasive West Nile virus can have serious consequences. Patients develop stiff necks and suffer terrible headaches. “They’ll describe it as the worst headache of their life,” Murray says. There’s no specific treatment for the disease, so doctors can only treat the symptoms and hope for the best. Many patients with neuroinvasive infections don’t fully recover. “In meningitis cases, about 40 percent never make it back, and in encephalitis cases, (the figure is) 80 percent,” Murray says.
Scientists don’t know what determines the severity of West Nile virus infection. “Most people don’t get neuroinvasive disease,” says Robin S. Klein, a physician and neuroimmunologist at Western University in Ontario. Older people and those with compromised immune systems seem more likely to develop severe West Nile virus infection, but even young, healthy people can get it. “We don’t know exactly why some people get invasive disease,” she adds.
There is currently no approved vaccine for West Nile, and although some candidates have shown promising results in early trials, efforts have been slowed by a lack of profit incentives. And the virus, transmitted by several species of mosquitoes and primarily infecting birds, which cannot follow public health guidelines the way humans can, will likely never go away.
The only sure way to avoid the disease is to avoid being bitten by mosquitoes that carry the virus. West Nile virus is most commonly found in mosquitoes of the genus Culicoides. Ieca, Other types can be carried as well. And Ieca Mosquitoes like to hang out around humans and bacteria-rich environments, says Vázquez-Prokopec. “Mosquitoes are the cockroaches of the mosquito world,” he adds. “In fact, they have evolved and adapted to bite people and to live in urban areas.”
Local governments often try to eradicate mosquitoes with pesticides and habitat removal, but Murray warns against relying solely on these efforts to protect against West Nile. “We’re doing the best we can to reduce mosquito populations, but it’s not a perfect science,” Murray says. “There are always challenges.”
These insects bite most at night, Ieca Mosquitoes are common, so people should take extra precautions against them this time of year, especially wearing long sleeves and pants, using a CDC-approved insect repellent to reduce bites, and getting used to taking mosquito risks seriously, Vásquez-Prokopec recommends. “The future of urban life in the United States is, in some ways, a buggy future,” he says.
