Officials warn of 2 possible measles exposure sites in Montgomery County, Pa.

ABINGTON, Pennsylvania (WPVI) -- Health officials in Montgomery County, Pennsylvania are working to identify and contact residents who may have been exposed to a measles patient.

That patient is from Philadelphia, where city health officials have confirmed eight cases so far.

SEE ALSO: 8 measles cases now identified, Philadelphia health officials say

The infected patient visited two locations earlier this month:

Holy Redeemer Pediatric Urgent Care-Meadowbrook

• 1648 Huntingdon Pike, Meadowbrook, PA 19046

• January 3, between 3:30 p.m. and 7:30 p.m.

Jefferson Abington Hospital Emergency Department

• 1200 Old York Road, Abington, PA 19001

• January 3, between 7 p.m. and 9:40 p.m.

"It's important to remember that not everyone who was at these sites on the dates and times above was exposed. The Health Department or the facility will contact you if you were exposed," the Montgomery County Office of Public Health said in a statement on Thursday.

Health officials released the following information about measles immunity:

People are immune to measles if they:

- Were born before 1957.

- Have already had measles.

- Have received two doses of measles-containing vaccine (usually given as measles, mumps, and rubella - or MMR - vaccine) and aren't immune-compromised.

If you are immune to measles, you don't have to do anything - even if you were in those buildings on the dates listed.

If you're not immune to measles:

- You should take precautions if you may have been exposed and aren't immune to measles. This includes infants under the age of 12-15 months, who typically haven't been vaccinated yet. If you or your child aren't immune, you should:

- Contact your healthcare provider or pediatrician right away, especially if you don't feel well. Tell your doctor about your possible measles exposure.

- Alert your healthcare provider before visiting. Tell them that you've been exposed to measles and ask them to call the health department.

- Stay home. You could give measles to vulnerable people, so you must quarantine.

"It is the most contagious infectious disease that's preventable," said Dr. Paul Offit, director of the vaccination center at Children's Hospital of Philadelphia. "And the reason is, you don't have to have direct contact with somebody who has measles."

Offit says you only have to be in the same airspace as an infected patient within two hours.

A renowned virologist and author, Dr Offit says a decrease in vaccination rates is to blame for this outbreak.

"What's happened is there has been an erosion in vaccine rates. The CDC recently put out a report in November showing the immunization rate among kindergarteners had dropped to as low as 92%" he said.

That's below the required levels for herd immunity.

Infected patients can expect a high fever, dry cough, fatigue, and a rash. Healthcare professionals can only hope the outbreak is contained.

"It is very frustrating because we have here one of the clear examples of a vaccination that can prevent a disease," said Dr. Richard Lorraine, the medical director for the Montgomery County Office of Public Health. "And we really do wish more people would take advantage of it."

Montgomery County officials believe they have contacted everyone who may have been exposed. If they're not vaccinated, they've been asked to quarantine for 21 days.

----

Dr. Paul Offit is the author of "Tell Me When It's Over," a book about navigating a post-pandemic society.