JONATHAN M. METSCH, Dr.P.H. – Tracking Emerging Public Health Challenges – September 27, 2026– MEASLES
“In 2000, measles was declared eliminated in the United States. Twenty-six years later, we are talking about it again.
I have only ever known this disease as a box checked off on my childhood vaccination records, so its return feels almost out of place.
This year, thousands of cases have been reported across the country, with outbreaks reaching communities that haven’t seen widespread transmission in decades.
How does a disease come back after we supposedly got rid of it?
The answer has less to do with the actual measles virus changing and more to do with the conditions surrounding it. Measles never disappeared from the world, and because it is one of the most contagious viruses we know of, keeping it under control depends on maintaining an unusually high level of immunity within a community. Gaps in that protection can grow, ultimately allowing the virus to return.
To understand this, it is important to know what makes measles so remarkably good at spreading.
Measles is a respiratory virus that spreads through the air when an infected person coughs, sneezes, talks or even breathes. Virus-containing particles can remain in the air for up to two hours after an infected person has left the area. Among people without immunity, roughly 90 percent of those who are exposed will become infected.
Epidemiologists measure this contagiousness using a number called R0. It estimates how many people one infected person can transmit a disease to in a population with no immunity. Measles has an estimated R0 between 12 and 18, meaning a single infected person could theoretically spread the virus to 12 to 18 others. For comparison, estimates for the original strain of COVID-19 were closer to 2 to 3.
This extraordinary ability to spread is why even relatively small gaps in immunity can make a difference.” (1)
“On September 13, a traveler with measles passed through Philadelphia International Airport, moving between terminals over hearly five hours. Six days later, the city’s health department issued an exposure warning.
The warning concerned a single traveler. The public-health problem it illustrated was considerably larger.
“Epidemiologically, this is news buzz,” Dr. Matthew Ferrari, director of the Center for Infectious Disease Dynamics at Penn State, told me. Operationally, though, it is something else. Airport exposures generate large numbers of people who develop routine fevers after passing through a terminal — contacts who must be tracked down, tested, and cleared, and who turn out, almost always, not to have measles. Each one costs time from a public health workforce already choosing where it can afford to respond. “For a response that is already strapped for resources,” Ferrari said, “this is a hit they shouldn’t have to take.”” (2)
The Pennsylvania department of health (DoH) announced on Friday that 55 new measles cases had been reported in the state since Wednesday, with officials continuing efforts to contain an outbreak of the disease that has spread across dozens of counties.
In a news release, the DoH said that 890 measles cases had been confirmed across 39 counties in the state so far for the year. The outbreak had resulted in 173 hospitalizations in the state and four measles-associated deaths, the statement added.
State health officials said fewer than 1% of reported cases have occurred among individuals vaccinated against measles. And according to the state data, 31% of the cases are among people younger than 18.” (3)
Measles is spreading through Pennsylvania’s Amish country. Doctors are scrambling to keep up, https://www.ms.now/news/measles-pennsylvania-amish-outbreak
In Amish country, nurses go door to door to stop deadly spread of measles, https://www.bbc.com/news/articles/ck3wjyjgj37po
“At least six babies in Pennsylvania have been born infected with measles, with two so sick they had to be admitted to intensive care. The growing outbreak is raising alarm among doctors who are treating the potentially deadly condition. Congenital measles is a disease that’s rarely, if ever, seen in the U.S.” (3)
What can Pennsylvania learn from the Texas measles outbreak?, by Hanna Webster, https://www.post-gazette.com/news/health/2026/09/27/pennsylvania-texas-measles-outbreak/stories/202609250052
(Bangladesh) Nine more children die with measles-like symptoms in 24 hours, http://www.daily-sun.com/bangladesh/900120/nine-more-children-die-with-measles-like-symptoms-in-24-hours
US CDC confirms first measles-related death of 2026, does not disclose state, By Siddhi Mahatole, https://www.reuters.com/business/healthcare-pharmaceuticals/us-cdc-confirms-first-measles-related-death-2026-09-23/
“Heidi Overton, the White House’s nominee to lead the Food and Drug Administration, told senators Thursday that the measles, mumps and rubella vaccine “is not lethal,” contradicting President Donald Trump’s recent statements about the shot.
Under questioning by Senate HELP Chair Bill Cassidy (R-La.) at her confirmation hearing, Overton said every vaccine on the U.S. market is “safe and effective, according to the FDA.” The MMR vaccine, she said, is the best public health tool to respond to the ongoing measles outbreak.” (4)
1.The Science Behind It: How Did Measles Come Back?, By Yuvika Salman, https://fullertonobserver.com/2026/09/27/the-science-behind-it-how-did-measles-come-back/
2.Measles Has Returned To America. We’re No Longer In Containment Mode, By John Drake, https://www.forbes.com/sites/johndrake/2026/09/26/measles-has-returned-to-america-were-no-longer-in-containment-mode/
3.Pennsylvania measles outbreak spreads, with 55 new cases reported since Wednesday, by Anna Betts, https://www.theguardian.com/us-news/2026/sep/26/pennsylvania-measles-outbreak-spread“
4.FDA nominee contradicts Trump on safety of measles vaccine, by Lauren Gardner, https://www.politico.com/live-updates/2026/09/24/congress/fda-nominee-safety-measles-vaccine-01091494
curated by Jonathan M. Metsch, Dr.P.H.
Clinical Professor of Environmental Medicine, Icahn School of Medicine at Mount Sinai