A ninth case of measles has been confirmed in connection with the outbreak in Philadelphia, the city's health department reported Jan. 17.
Eight of those cases are in Philadelphia and one is outside, according to officials. Two of the most recently added locations of exposure risk on the health department's website are listed in Meadowbrook, Pa., and Abington, Pa.
The case outside of Philadelphia, but still connected to the outbreak, occurred nearby in Delaware.
The city is also now offering vaccinations at multiple locations, only requiring a piece of mail with an address as identification for anyone interested in receiving the measles, mumps and rubella vaccine for free.
The latest case is the first additional one to be confirmed since Jan. 5. The epicenter of the outbreak was determined to be from an index case at the Children's Hospital of Philadelphia in late December and early January.
Exposed patients who did not follow quarantine protocols and returned to daycare caused additional spread in the city, according to officials.
The northeast is not the only area of the U.S. to currently experience pockets of measles cases and outbreaks. On Jan. 12, health officials in Missouri confirmed a case and also issued an exposure warning. There have not been any additional cases confirmed in connection with the Missouri case.
A Colorado resident also tested positive for measles in late December, marking the state's first case in five years.
"The fact that we're seeing sporadic measles cases, to me, says that we probably have pockets in the United States where we're not doing a good job vaccinating, and I'm worried that this is a trend that's been getting worse over the years," Peter Hotez, MD, PhD, a pediatric expert and co-director of the Texas Children's Hospital Center for Vaccine Development, told ABC News Jan. 18.
Both the CDC and the World Health Organization issued a warning in November of a "staggering" increase in measles cases and deaths across the globe, as fewer are vaccinating against the virus.
Measles cases are also now increasing across the U.K. as vaccinations against it has declined there as well, Forbes reported Jan. 18.