Health officials issued a warning after a person with measles spent time at Chicago’s O’Hare International Airport.

The possible exposure took place at O’Hare on April 22 and April 23, between 10 a.m. and 8 p.m., especially in Terminal 1, according to Illinois public health officials.

The warning raised concern because measles is extremely contagious.

It spreads through the air when an infected person coughs or sneezes. The virus can also remain in the air for up to two hours after the infected person has left the area.

That makes airports a sensitive place for exposure.

Large crowds, enclosed spaces, and travelers moving quickly between gates can make contact tracing difficult.

Officials said the confirmed case involved an adult Chicago resident who had traveled internationally through O’Hare. The person had received one prior dose of the measles vaccine and later developed a rash on April 25.

The individual isolated at home after diagnosis.

Soon after, public health officials confirmed another measles case in Cook County. Authorities began monitoring contacts and looking for any possible connection between the cases.

Measles often begins with symptoms that can look like a common cold.

People may develop fever, cough, runny nose, and red or watery eyes. A rash usually appears later.

Health officials urge anyone who may have been exposed to watch for symptoms and contact a healthcare provider before going to a clinic or emergency room. This helps prevent possible spread to others.

Vaccination remains the strongest protection.

The CDC says one dose of the MMR vaccine is about 93% effective against measles, while two doses are about 97% effective.

That means vaccinated people are far less likely to become seriously ill, but no vaccine is 100% perfect.

Anyone unsure about their vaccination status should check their records or speak with a healthcare provider.

The key message is simple.

Do not panic.
Do not ignore symptoms.
Check your vaccine history.
Call ahead before seeking medical care if measles is possible.

For most protected people, the risk is much lower. But because measles spreads so easily, even one case in a busy airport can trigger a serious public health response.