Health officials say a measles outbreak in Pennsylvania has grown to nearly 700 cases, making it one of the larger outbreaks the state has dealt with in recent memory.
Measles is among the most contagious viruses known, capable of spreading through the air and lingering in a room for up to two hours after an infected person leaves. It causes fever, cough, and a distinctive rash, and can lead to serious complications including pneumonia and, in rare cases, brain swelling, particularly in young children. The measles, mumps, and rubella vaccine, given in two doses starting around a child's first birthday, is highly effective at preventing infection, and the United States declared measles eliminated domestically in 2000 thanks to widespread vaccination.
Since then, outbreaks have periodically returned, generally tracing back to travelers who contract the virus abroad and introduce it into communities with pockets of lower vaccination coverage, where it can then spread locally. Pennsylvania's outbreak fits into a wider pattern of elevated measles activity across the country over the past couple of years, as public health officials have worked to contain clusters in several states through vaccination campaigns and monitoring.
Health departments typically respond to outbreaks like this one by identifying exposure sites, offering vaccination clinics, and, where necessary, recommending exclusion of unvaccinated individuals from school or work if they may have been exposed, standard tools for containing a virus this contagious.
Watch for updated case counts from Pennsylvania health officials and for any expanded vaccination clinics in affected counties.
How is measles usually stopped once it starts spreading?
Health departments identify exposure sites, run vaccination clinics, and in some cases ask unvaccinated people who may have been exposed to stay home from school or work.
Is there a vaccine for measles?
Yes, the MMR vaccine, typically given in two doses starting around a child's first birthday, is highly effective at preventing infection.