Health experts are closely watching for any sign of possible measles spread in the St. Louis area - following a case that recently passsed through Lambert Airport.
"Measles is the most contagious viral illness that we know. It is sort of the 'Grand Daddy' of contagiousness," says Washington University Medicine infectious diseases specialist Dr. Steven Lawrence.
"On average, if you had a room full of people that had not been previously vaccinated, in other words they were completely susceptible to it, this virus on average would impact about 15 other individuals. So, it really does have more contagiousness than any other viral illness that we know of."
Both the Missouri and the Illinois Departments of Public Health confirm an adult with measles flew into Terminal 2 at Lambert Airport on February 7th and then took a shuttle to get their car before driving to Collinsville and attending services at Good Shepherd Lutheran Church the following day.
After exposure, measles symptoms can take from 7 to 21 days to develop.