As of July 24, 2018, the Centers for Disease Control and Prevention reports that people have contracted West Nile virus in Alabama, California, Illinois, Louisiana, Maryland, Mississippi, Nebraska, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, South Dakota, and Texas. It’s a reportable illness, meaning that if your doctor diagnoses you, they will let the state and CDC.

West Nile Virus has its moment every summer and fall, and in recent weeks many states have started reporting their first human cases of the season. Here’s what to know about this mosquito-borne illness.

Where Is It?

As of July 24, 2018, the Centers for Disease Control and Prevention reports that people have contracted West Nile virus in Alabama, California, Illinois, Louisiana, Maryland, Mississippi, Nebraska, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, South Dakota, and Texas. It’s a reportable illness, meaning that if your doctor diagnoses you, they will let the state and CDC know.

Historically, West Nile has been found in all 48 states of the continental US. In addition to waiting to hear about cases in humans, some states also test mosquitoes or birds for the virus.

How Bad Is It?

Most people, about 80 percent, don’t have any symptoms when they contract the virus. For those who do show symptoms, the most common one is a fever, which may be accompanied by headaches, body aches, nausea, diarrhea, or a rash. These symptoms are common to many illnesses, though, so if you get sick you should make sure to get checked out.

In rare cases (less than one percent), the infection can lead to a dangerous inflammation of the brain (encephalitis) or the membranes around the brain (meningitis). Even more rarely, this can lead to death. Symptoms include neck stiffness, disorientation, muscle weakness, and more. The CDC has more information on symptoms here.

What Can a Doctor Do?

When you seek help, your provider can order a test for West Nile virus. Since it’s a virus, antibiotics won’t help; there is no treatment that can make the virus go away. But your doc can help you get supportive care to ride out the illness, whether that’s pain relievers for a mild case, or hospitalization for the rare serious symptoms.\

How Can I Prevent It?

West Nile virus is carried by mosquitoes, so make sure not to leave standing water around your yard. (Baby mosquitoes are aquatic, so in order to breed, they need ponds and puddles and that bucket you forgot about last fall.)

Prevent mosquito bites when you’re out and about with bug spray: DEET or another EPA-registered bug spray on your skin, and permethrin on your hiking boots and other outdoor clothes. (Conveniently, this is the same one-two punch that protects well against ticks.) Screens and mosquito netting work, too. For babies too young for bug spray (under two months), you can cover their stroller with mosquito netting.