Illinois health officials reported the state’s first case of measles in four years Friday.

The Cook County Health Department reported the suspected case Tuesday to the Illinois Department of Public Health. It was confirmed the next day by state health officials.

The person, who was exposed to the virus in another country, was unvaccinated, the IDPH said.

“This first reported case of measles in Illinois since 2019 is a reminder that this disease can be prevented with up-to-date vaccination,” IDPH Director Dr. Sameer Vohra said in a statement. “Two doses of measles vaccine are 97% effective in preventing measles. However, as we saw this week, it still can affect those who are unvaccinated.”

Measles symptoms include rash, fever, cough, runny nose and red, watery eyes. Symptoms can take from a week up to three weeks to develop after exposure.

The onset of the rash in the most recent case appeared Monday, meaning the infectious period would have lasted from Oct. 5 to Friday, officials said.

State and county health officials are investigating potential exposure locations throughout the country, the IDPH said.

Measles is an airborne disease that spreads through coughs and sneezes, or through mucus and saliva. It can cause serious complications, such as swelling of the brain and pneumonia.