HARRISBURG, Pa. (CBS) – The Pennsylvania Department of Health is advising the public about a potential exposure to a case of measles in Delaware and Philadelphia counties.

A person who likely has measles may have exposed others at the following locations:

CVS Pharmacy, located at 316 E. Lancaster Avenue, in Wayne, Pa. on Sunday, December 28, from 5:30-8 p.m.

Please Touch Museum, Memorial Hall, Fairmount Park, 4321 Avenue of the Republic, in Philadelphia on Monday, December 29, from 3:30 to 5 p.m.

Health officials say the vaccine for measles is highly effective, however, the following groups of people are at risk if they had contact with an infected individual:

Infants less than one year of age who are too young to have received the measles, mumps and rubella (MMR) vaccine

Individuals who were vaccinated with an inactivated vaccine, which was used from 1963 through 1967, and have not been revaccinated

Individuals born after 1957 who have only received one dose of MMR vaccine

Individuals who refused vaccination

Individuals from parts of the world where there is low vaccination coverage or circulating measles.

Officials say symptoms begin about one to two weeks after exposure and include a runny nose, watery eyes, cough and high fever. After four days, a raised, red rash starts to spread on the face, down the body and out to the arms and legs, lasting usually four to seven days.

An individual with measles can spread the virus to others for four days before and four days after the rash begins, according to health officials. It can spread by sneezing, coughing, touching contaminated objects and direct contact with infected nasal or throat secretions.

Infected droplets and secretions may remain contagious on surfaces for up to two hours.

The MMR vaccine can help prevent infection if it is given within three days of exposure. If it has been more than three days since exposure, a dose of immune globulin can provide protection up to six days after exposure, officials say.

There is no risk in getting an additional dose of the MMR vaccine.

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