Iowans have been exposed to measles. Here's what you should know about the contagious disease.

Two restaurants in the Des Moines metro were visited in April by a confirmed measles patient from Missouri, potentially infecting Iowans with the highly contagious disease.

Measles is considered one of the most infectious viruses around and often has serious, sometimes deadly, complications. There is no treatment for the illness, but it can be prevented through a vaccine.

"This is just not a disease that you want to get at all," said Dr. Patricia Quinlisk, medical director at the Iowa Department of Public Health. "We don't want people to think 'this is no big deal, it's a mild disease, don't worry about.' One of the reasons we have a vaccine for it is because it can be very bad."

Anyone who was at the same location as the patient needs to contact their doctor right away if they begin to show symptoms of measles.

The patient visited these restaurants:

Hardee's, 3621 Merle Hay Road in Des Moines, between 8:15 a.m. and 11:45 a.m. on April 13, and

Panera Bread, 2310 Southeast Delaware Ave. in Ankeny, between noon and 4 p.m. on April 16.

We've compiled some news-to-know about the disease:

How does it spread?

The disease spreads through the air when an infected person coughs or sneezes. If one person has it, 9 out of 10 people will also become infected if they are not vaccinated, according to the Centers for Disease Control and Prevention.

The virus stays in the air up to two hours after an infected person has left. Patients can spread the disease four days before knowing they have measles and up to four days after they're diagnosed.

Database: School vaccination rates in Iowa

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How can I tell that I have measles?

Symptoms of measles include fever, cough, runny nose, watery eyes and a red rash that starts on the face and moves to the rest of body.

The fever usually develops seven to 18 days after the infection and the rash approximately two weeks after the infection. Symptoms can last up to two weeks.

A doctor can test for the virus if you present symptoms. Doctors cannot tell whether you've been exposed, but they can test for immunity to measles.

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I have those symptoms. What should I do?

Do not leave your house for any reason. Call your medical provider, describe your symptoms, and arrange to be seen safely. Often your doctor will arrange to see you after hours.

"We don't want them to go to the doctor's office, sit in the waiting room next to a little baby or a kid with leukemia and spread measles to them," Quinlisk said.

When was the last outbreak in Iowa?

Measles in Iowa has been rare. The Iowa Department of Public Health has reported 37 confirmed cases of measles since 1995. The last case was reported in 2011.

Most measles cases in Iowa were brought back by unvaccinated people who traveled to countries where the disease is more common.

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I was at that restaurant, but don't have symptoms. What should I do?

Check your medical records to verify that you've received two doses of the measles-mumps-rubella, or MMR, vaccine. Your doctor can also test to see if you're immune to the disease.

"We want all Iowans to make sure they're fully vaccinated," Quinlisk said. "And if for some reason they're not, now would be a really good time to get vaccinated."

A vaccine will not prevent you from getting measles if you're already infected, but it will protect you the next time you may be exposed.

What happens if I have measles?

There is no treatment for the illness. Measles can be serious for anyone who contracts it, though children younger than 5 and adults older than 20 can have more serious complications.

Common complications include ear infections and diarrhea. Some ear infections can result in permanent hearing loss.

Serious complications include pneumonia and swelling of the brain. For every 1,000 children who get measles, one or two will die from it, the CDC says.

Pregnant women may give birth early if they contract measles.

Subacute sclerosing panencephalitis, a rare but fatal disease of the central nervous system, can develop 7 to 10 years after a person has measles. That disease is rarely reported in the United States, according to the CDC.

Why are some people not vaccinated?

Babies under 12 months old cannot be vaccinated and neither can people who have other underlying diseases, such as cancer or HIV/AIDS.

Others don't get vaccinated under Iowa's religious exemption law. Iowa parents have to sign a statement saying immunization conflicts with "a genuine and sincere religious belief, and that the belief is in fact religious, and not based merely on philosophical, scientific, moral, personal, or medical opposition to immunizations."

In the 2016-17 school year, 7,465 Iowa children had religious exemptions to vaccination, compared to 1,891 students who had medical exemptions.

Why is measles here now?

From January 1 to March 30, 34 people from 11 states — Arkansas, California, Illinois, Indiana, Kansas, Michigan, New York, Oklahoma, Pennsylvania, Tennessee, and Texas — had measles, according to the CDC.

Kansas has had 18 confirmed cases of measles in several counties since March 8. Those cases have been traced back to a day care.

Missouri now has four confirmed cases of measles, all out of the Kansas City area. The patient who exposed Iowans was traveling through the state from Missouri.