An image of several flying mosquitoes, potential vectors of West Nile virus.

When it comes to mosquito-borne illness, Zika may have been your top concern over the previous two summers.

But West Nile—which is transmitted to people by mosquitoes who’ve fed on birds infected with the virus—has actually been the most common mosquito-borne illness in the U.S. for a number of years.

You may be hearing news reports about the West Nile virus—which can cause flu-like symptoms but be fatal in rare instances—because the first diagnosed cases are beginning to emerge.

Should you be worried? And could it become as significant a problem as Zika? Here’s what you need to know.

The Risk of Getting It Is Low

Although the virus has historically been more prevalent in Louisiana, Mississippi, the Dakotas, Nebraska, Wyoming, and Colorado, according to the Centers for Disease Control and Prevention (CDC), it can be found across the continental U.S. And the likelihood of an outbreak in any area may depend on a variety of factors—including how much standing water is around, irrigation patterns on farms, and the weather and type of mosquito most often seen there.

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Overall, though, the chances that you’ll catch it appear to be small. Usually only a few thousand cases are reported to the CDC each year—in some years the total has been as low as around 700 cases and by far the most ever reported was almost 10,000.

Between 2013 and 2016, the U.S. saw no more than 2,500 reported cases a year. (For comparison, since 2008 more than 30,000 cases of Lyme disease have been reported to the CDC every year.) 

One caveat: Many people with West Nile virus don't know they have it (see below for the reasons), so it may often go unreported. That means the true number could be up to 30,000 to 100,000 cases a year, says Marc Fisher, M.D., a medical epidemiologist with the CDC.

Should You Worry If You Get It?

Generally, no. In fact, only one in five people with West Nile infections even has symptoms. And when fever, headache, body aches, joint pain, and less commonly, a faint rash, do arise, they're usually mild and go away within a few days, says Luis Marcos, M.D., associate professor of clinical medicine in the division of infectious diseases at Stony Brook University. 

So if you suspect you have West Nile virus (flu-like symptoms can arise approximately 3 to 14 days after you’ve been bitten by mosquitoes), you can simply wait it out. If needed, you can ease symptoms using over-the-counter pain relievers and fever reducers, such as acetaminophen (Tylenol and generic), ibuprofen (Advil and generic), or naproxen (Aleve and generic).

Pay Attention to These Danger Signs

In a small number of cases—less than 1 percent—the illness becomes “neuroinvasive,” infecting the brain or spinal column. This can ultimately cause serious problems, including a paralysis that resembles polio, coma, and blindness. About 10 percent of people with neuroinvasive West Nile virus die, according to the CDC.

So be on the lookout for severe headaches, neck pain, sensitivity to light or fear of light (photophobia), and confusion, says Sandro Cinti, M.D., professor of infectious diseases at Michigan Medicine in Ann Arbor and at the VA Ann Arbor Healthcare System.

If you notice any of the above, see a doctor right away, Cinti says. You may need to be hospitalized. And note that neuroinvasive West Nile is more likely to occur in people who have weaker immune systems, notably older adults.

Take Steps to Protect Yourself

Currently, there is no vaccine against West Nile virus, so the best way to protect yourself is to avoid mosquito bites. A key tool: an effective insect repellent.

In Consumer Reports’ testing, we’ve found that the most effective repellents contain 15 to 30 percent deet, 20 percent picaridin, or 30 percent oil of lemon eucalyptus. (CR members can see our top-rated insect repellents here.) Use repellent on all exposed skin, but don’t apply it under your clothing.

Wearing long sleeves and pants when you’re outside in mosquito-infested areas can also help. In addition, eliminate sources of standing water—where mosquitoes breed—around your home. These include birdbaths, buckets, planters, flowerpots, and, Cinti says, unused tires, which are especially hard to dry out.