NEWARK, N.J. -- Health officials are warning people who went through airports in Newark, New Jersey, Detroit and Memphis this month that they may have been exposed to measles. The disease was carried by two air passengers from overseas.

The two cases happened within days of each other. The first was on March 6, when a contagious passenger flew from an unknown origin abroad to Detroit Metropolitan Airport and was later hospitalized. The second involved a young child from Brussels who flew into Newark Liberty International Airport, then went to Memphis, where the child was isolated.

The New Jersey Department of Health warned anyone in Terminal B or Terminal C in Newark between 2:45 p.m. and 9:00 p.m to seek medical attention if they develop symptoms.

Health officials are warning about two recent measles cases CBS News

CBS News chief medical correspondent Dr. Jon LaPook says measles is very contagious, since it can spread through the air. But there's some good news for passengers.

"The measles virus only lasts for two hours or less, on a surface or in the air," said Dr. LaPook.

As for symptoms, Dr. LaPook says that can be tricky.

"It can be just like any other virus," he said. "So you have a little bit of a sore throat or runny nose or pink eye, then fever, and then you can come down with that classic rash."

He also says the best thing you can do to protect yourself is be immunized. Last year, there were 118 cases of measles in the U.S., mostly among people who were not vaccinated.

People most at-risk are children under age 5, people with weak immune systems and pregnant women. The vaccination rate for measles in the U.S. is around 90 percent, and if you've been vaccinated, you're 97 percent protected and you don't need another booster.