India, May 2 -- U.S. health authorities have warned the public to stay alert as the Chicago O'Hare International Airport faced a potential measles exposure. An adult with the virus was transferred between Terminal 1 on April 22 and 23 from 10 a.m. to 8 p.m., possibly infecting hundreds of travellers with this highly transmissible pathogen.

The individual had received one dose of the MMR (measles, mumps, rubella) vaccine but still contracted the disease, developing a rash by April 25.

Days later, a second measles case was confirmed in another adult from the same Illinois county. Their vaccination status is unclear, but they were quickly isolated after checking into a local hospital on April 28.

"These are the first two cases reported in...