After a young child with measles came to Providence Little Company of Mary Medical Center in Torrance on Jan. 9, the hospital notified 37 emergency room patients that they might have been exposed.
Even if the patient didn't have a rash, it can still be extremely contagious.
"Four days prior to them breaking out with the rash, they are carrying the virus," said Dr. Martha Rivera, a pediatric infectious disease expert at White Memorial Medical Center.
Experts say the measles virus can live on surfaces up to two hours, and even people who have been vaccinated can still get infected. That's because not everyone gets both doses.
"It's a 95 percent effective vaccine. It's a very good vaccine, but you need two doses," Dr. Rivera said. "Some of us don't respond to vaccines."
List of potential exposure locations and times
The measles, mumps and rubella, or MMR, vaccine is first given at 12 months. Then, a second or booster shot is given between four to six years of age. That takes eight days to become effective.
And Dr. Rivera says depending on when you were born, a booster shot can give you even more immunity.
"It's thought that, if you were born before 1957, we were all exposed to measles so we have a natural immunity because we were exposed or we had natural measles," Dr. Rivera said.
One way to see how much immunity you have to measles is to get a blood test. Dr. Rivera says this will tell doctors the level of antibodies in your body. It's a simple blood draw with results in about 12 hours.
"That would be a way to prove that you have protection against this disease," Dr. Rivera said.
When in doubt, she recommends people get a booster shot just to protect themselves.
"There is no risk of autism, that was dis-proven, so it is a good, safe vaccine and all the fear factors have been taken away," Dr. Rivera said.
Symptoms include cough, runny nose, red eyes and a red-spotted rash. Measles can lead to pneumonia, brain damage and death. From 2001 to 2013, 28 percent of young children who had measles had to be hospitalized.
For more information about measles, visit publichealth.lacounty.gov/ip/DiseaseSpecific/Measles.htm.