Measles outbreak in Pennsylvania poses risks beyond US borders, experts warn

Pennsylvania has recorded more than 1,200 measles cases and over 240 hospitalisations across 42 counties this year, state officials say, as the US Centers for Disease Control and Prevention (CDC) announced the country’s third measles death of the year. The state sought emergency CDC support in September, and on October 5 New York Governor Kathy Hochul declared a state disaster emergency in rural areas to expand vaccination and testing. “No one should get seriously ill or die from a vaccine-preventable disease,” Hochul said.

Matt Ferrari, director of Pennsylvania State University’s Center for Infectious Disease Dynamics, said the US had been so successful at eliminating measles that it had “the luxury to forget” the virus was serious. “We have been able to forget how nasty measles is,” he told Al Jazeera. Vaccination coverage among US kindergartners has fallen from 95.2 percent in 2019-2020 to 92.4 percent in 2025-2026. Experts warn that declining coverage in one place can leave people thousands of miles away vulnerable, and that lower rates put immunocompromised people at greater risk.

Local outbreak, global risk

Pennsylvania reported in August that two unvaccinated people died of measles in Lancaster County, home to the nation’s oldest Amish and Mennonite communities. Joshua Good, principal of Ephrata Mennonite School, where two students contracted measles earlier this year, helped organise a pop-up vaccination clinic with state officials. He said the response was productive but that the Mennonite community still holds significant vaccine scepticism, with families making decisions based on their own judgement rather than lack of access. Vaccination rates remain below the threshold for herd immunity.

Public health officials advocate building trust before outbreaks. Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health, told Al Jazeera that health workers cannot simply arrive in an emergency and make people feel blamed or shamed. “You need to know them so that they see public health as a resource rather than law enforcement,” she said. She warned that low coverage and distrust allow measles to spread even when vaccines are available.

The continental Americas became the first WHO region to eliminate endemic measles transmission in 2016. PAHO says regional coverage remains below the target for both vaccine doses. Canada became the first country in the Americas to lose its elimination status last year after an outbreak that began in 2024. A country can lose status when the same measles genotype circulates for at least 12 months. Dr Daniel Salas of PAHO said Mexico and Bolivia will also be closely assessed. Some have warned the US may be on track to lose its status this year.

US Health and Human Services Secretary Robert F Kennedy Jr has defended the US response, saying at an August 26 event in Florida that the country was doing a better job than any other at controlling the outbreak and citing higher case numbers in Mexico, Canada and Britain. Nuzzo disputed that, saying repeated outbreaks show a country struggling to contain transmission. Dr Salas said action within the first three days after a suspected case is critical, and authorities should not wait for laboratory confirmation. Scientific journals found the virus strain in Canada’s latest outbreak was genetically linked to US Mennonite cases.

Nuzzo said the US spread imperils other countries. “It’s easy to kind of point to other countries and say that they’re the problem, but the reality is we’re all dependent on each other, and it’s very hard to protect ourselves when measles is spreading elsewhere,” she said.

Source: Al Jazeera.