Health officials are sounding the alarm over a potential measles exposure at Chicago O’Hare International Airport.

An infected adult was mainly confined to the airport’s Terminal 1 area, potentially exposing hundreds of others to the world’s most infectious disease.

The person was at the airport – the world’s fourth busiest in terms of passenger numbers – on April 22 and April 23 between 10am and 8pm both days.

They had had one prior dose of the MMR vaccine but they went on to develop a rash on April 25 and tests confirmed they had contracted measles. 

Since being being diagnosed, they have been been isolating home. 

Another case was identified days later in an adult living in the same county in Illinois. 

Their vaccination status is unknown, but they checked into to a local hospital for treatment on April 28 and medical staff quickly isolated them.

Officials are warning anyone who fears they may have been exposed to contact their health provider and monitor for symptoms in what is the latest in a string of measles scares to rock America’s major airports and surrounding neighborhoods.

Health officials are sounding the alarm over a potential measles exposure at Chicago O’Hare International Airport 

Other locations that are points of potential exposure in Illinois include the Chicago Public Library, the Fittingly Delicious health food restaurant in Chicago, the Aldi in Lyons, a Shell gas station in Stickney and a Mobil gas station in Berwyn.

The infected persons visited these locations between April 21 and 28. They mark the first two cases in the Cook County region of Illinois this year. 

In the past few months, New Jersey’s Newark Liberty International Airport and John F. Kennedy airport along with hubs in Washington DC, Seattle and Los Angeles were all plunged into chaos over measles alerts.

It comes amid a major outbreak in West Texas, that has already sickened around 650 people and led to two deaths, marking the first fatalities in a decade in the US.

Officials are warning anyone who may have been exposed to the virus in the Chicago area to monitor themselves for symptoms for the next two weeks, particularly if they are unvaccinated, and contact their health provider.

Anyone who develops symptoms is encouraged to immediately contact health services for treatment.

Officials say no infections linked to the infected individuals have been reported to date.

Commenting on the matter, Chicago-based public health worker Dr Olusimbo Ige said: ‘Chicago is no stranger to measles after our outbreak last spring and having contained it once we know we can do it again.

‘The MMR vaccine is an extremely effective tool for combatting illness and saving lives in our community, it’s never too late to get vaccinated and protect yourself from measles.’

Cold-like symptoms, such as a fever, cough and a runny or blocked nose, are usually the first signal of measles

Measles is one of the most infectious diseases in the world, with one person capable of spreading the virus to nine out of every 10 people they meet if those individuals are unvaccinated.

The infection is transmitted via breathing in infectious droplets that can remain suspended in the air for two hours after an infected patient passes.

Patients develop a fever, cough, and runny nose, which then develops into a rash that starts at the hairline before spreading to the neck, trunk, arms, legs and feet.

There’s no cure for measles, with doctors instead using antibiotics to treat related infections and IV fluids. 

If unvaccinated, about one in five people who are infected are hospitalized while one in 20 children develop pneumonia.

Among unvaccinated children infected with measles, about one in 1,000 will develop encephalitis — or swelling of the brain. And nearly one to three out of every 1,000 will die from the disease.

The vaccine is 97 percent effective at preventing an infection and is required for children attending school in some states.

In terms of when to get vaccinated, experts say children need two doses of MMR vaccine: the first dose at age 12-15 months, and the second dose at age 4-6 years. 

Babies ages 6-11 months should get an early dose if traveling internationally. Adults should also check to see if they are immune to measles.