Health officials are concerned about the outbreaks of measles in the United States and the United Kingdom.
As of January 16, nine cases had been identified in the measles epidemic being monitored by the state health department in Philadelphia.
The days of possible exposure varied from December 19 to January 7.
The health department published a list of addresses, including many hospitals and daycare centers, where people may have been infected.
Positive cases have also been reported in other US states, however they are not yet considered outbreaks.
The first case of measles to be confirmed in the state since March 2023 was reported by the New Jersey Department of Health on January 13. However, the actual cause of the case has not yet been verified.