Another person infected with measles at a Northeast day-care center as Philadelphia outbreaks grow to nine cases

Editor’s note: this story was updated with new information from the city.

A ninth person in Philadelphia has tested positive for measles, health officials said Tuesday.

The outbreak began last month at Children’s Hospital of Philadelphia and spread to a day-care center on Castor Avenue.

The latest case is the parent of a child who was previously infected at the daycare. It is the fifth infection related to the facility, according to the department of public health.

An unvaccinated child was exposed to measles while hospitalized at CHOP and subsequently attended the daycare center in violation of quarantine guidelines.

» READ MORE: Two more day-care children are infected with the measles. Here’s what to know about the outbreak in Philadelphia.

Previous cases included one unvaccinated adult and seven children. At least six of the people infected were hospitalized to treat the infection, and all were later discharged.

Authorities in Pennsylvania, Wilmington, and Delaware and Montgomery Counties have warned local residents of potential measles exposures from Philadelphia residents who visited health-care facilities outside the city.

Last week, a child in Camden County tested positive for measles. Authorities do not know where the child was exposed, and there is no known connection to the Philadelphia outbreak.

Camden officials warned the public about the following exposures:

Anyone who has been exposed in New Jersey and is not vaccinated or otherwise immune could develop symptoms from these exposures for several weeks, through Feb. 2, health officials warned.

Measles is highly infectious and spreads through breathing in an airborne virus or touching contaminated surfaces, according to the U.S. Centers for Disease Control and Prevention. By some measures, measles is seven times more contagious than COVID-19. The virus can remain in the air for two hours.

Even just one dose of the vaccine, which babies can receive when they are 12 months old, is 93% effective at preventing measles, according to the CDC. Two doses bring up that rate to 97%. People who were born before 1957 or have had measles are also considered immune.

The illness can be dangerous, especially for children under 5, pregnant people, and those with weakened immune systems.

A measles infection can lead to respiratory failure, inflammation of the brain, and death. In rare cases, the virus can cause a yearslong brain decline that results in death.

» READ MORE: Health department warns of measles cluster among unvaccinated residents that originated with CHOP patient

Measles symptoms appear up to two weeks after an exposure, according to the CDC. Initially, measles presents like a regular flulike illness: Patients may have a high fever, runny nose, and red, watery eyes. Three to five days after symptoms begin, the rash commonly associated with measles breaks out.

People with known exposure who are not vaccinated or otherwise immune should quarantine for 21 days.