A cluster of measles cases in Philadelphia has widened to include eight people over the past month, including at least five children, according to the city’s health department.
All of the cases were in people who had no immunity to the virus, Philadelphia Department of Public Health spokesperson James Garrow said.
A person who contracted measles outside the United States went to Children’s Hospital of Philadelphia in early December, the health department said, exposing three people at the hospital, including a parent and child in a nearby room, who later tested positive for the highly contagious virus.
The parent did not follow a quarantine and exclusion recommendation from the city health department, and the child attended a Philadelphia day care. Days later, two children from the day care were hospitalized with measles.
“The Health Department was notified that a measles case attended a day care facility on December 20 and 21 and exposed children and staff there,” the department said in a statement.
Health officials said Friday that they learned of three additional children at the day care center with possible cases of measles.
On Monday, the health department reported eight cases of confirmed measles: the first patient, four people at the day care and three people exposed at the hospital.
“All exposed people are offered appropriate post-exposure prophylaxis if within the recommended timeframe,” Garrow told CNN on Thursday. The MMR vaccine can be given within 72 hours of exposure, and immunoglobulin can be given within a six-day time frame, according to the US Centers for Disease Control and Prevention.
Philadelphia health officials added more locations and dates to the list of possible exposures that took place between December 19 and January 3. Anyone who might have been exposed is advised to quarantine for 21 days after exposure, Garrow said.
“It is important to stay home because it is so highly contagious and airborne and can hang around in the air for several hours,” said American Academy of Pediatrics spokesperson Dr. Christina Johns, a Maryland-based pediatric emergency physician at a PM Pediatric Care urgent care. “Additionally, I think that this is really a note for everyone to take about how quickly this infection can spread and so therefore the importance of vaccination. The only way to prevent the illness and then of course, the very concerning potential complications down the road from measles, is to get vaccinated.”
The department is offering free measles, mumps and rubella vaccinations for anyone in the city.
Experts recommend that children get the vaccine in two doses: the first between 12 months and 15 months of age, and a second between 4 and 6 years old. One dose is about 93% effective at preventing measles if you come into contact with the virus. Two doses are about 97% effective.
The Philadelphia health department says that 93% of kids in the city are fully vaccinated against measles by 6 years old.
Measles can spread when an infected person coughs or sneezes, lingering in the air for up to two hours after an infected person leaves a room. An infected person can also share germs by touching objects or surfaces.
It starts with symptoms typical of many respiratory illnesses, followed by a rash that usually starts on the face and spreads downward three to five days after symptoms begin.
“Measles is dangerous for anyone who is not immunized. Also, for the very young, those tend to be the most at risk for measles and its complications,” Johns said.
“There are some post-infectious complications that can include blindness, even. It can include some encephalitis, which is a rare but serious neurological condition that can happen even years later in life. So it is definitely not something to take lightly,” she said.
Although measles is considered eliminated in the United States, outbreaks are possible if an unvaccinated person travels to a country where the disease is still common, becomes infected and brings it back to the US, transmitting the virus to anyone unvaccinated.
“For most people who are fully immunized, the risk of measles exposure is low. However, it is very possible to transmit it to others who are more vulnerable,” Johns said. “So it’s important for everybody to do their part in an outbreak like this, to have awareness of the ongoing situation and to follow public health recommendations closely.”
Johns said outbreaks of vaccine-preventable diseases like this one are a “call to action” for members of a community to make sure they are up-to-date on their vaccinations.
“Many of these illnesses that people think are no big deal are really no big deal because we haven’t seen them in so long because of immunizations. And so it really is important to note that we’ve got to make sure that people are getting immunized, so we don’t see a resurgence of vaccine-preventable diseases,” she said.
About 92% of US children have been vaccinated against measles, mumps and rubella by age 2, according to a 2023 report from the CDC.
Before the nation’s measles vaccination program, about 3 million to 4 million people got the virus every year, and approximately 400 to 500 died.
There were 48 measles cases in 2023, the CDC reported.
The last significant measles outbreak in the US was in 2018-19 in Rockland County, New York, focused among unvaccinated children in Orthodox Jewish communities.