Flu winds down while measles ramps up in U.S.

Key takeaways:

• Influenza cases are declining.
• Measles outbreak continues.
• Avian flu cases are unchanged in the U.S.
• Meningitis update following isolated case.

Respiratory virus

Good news: nationwide, flu season is ending. Levels of acute respiratory illness are falling and rates of emergency department visits for these symptoms are low.  

This has been a particularly bad flu season, with more hospitalizations than in any other season in 15 years — as many as 1.3 million, according to a CDC estimate. Nationally, flu deaths in the 2024-2025 season are estimated to be between 26,000 and 130,000. 

Measles outbreak continues

As of April 11, some 712 confirmed cases of measles have occurred in the United States, with cases appearing in 24 states (Connecticut is not among them). (For comparison, the U.S. saw 285 measles cases in 2024.) The largest cluster of this preventable disease is in Texas and New Mexico, which currently involves 643 cases and two deaths. That is likely an undercount, as it is likely that some cases have not been reported to public health officials.

Some key points:

• Two previously healthy, unvaccinated children have lost their lives thus far. A man with measles in New Mexico has also died; the formal cause is under investigation.
• Vaccination prevents transmission and is safe and effective. But many cases are occurring in children too young to be safely vaccinated, thanks to the loss of herd immunity due to community vaccination falling under the protective 95% coverage rate.
• Vaccination efforts in Texas face ongoing challenges in the face of community hesitancy and inconsistent messaging from Department of Health and Human Services leaders. Vaccine clinics have been canceled due to federal funding cuts.
• Efforts by vaccine opponents to blame measles deaths on medical errors are not based in fact. On the other hand, children are reportedly experiencing liver damage from vitamin A toxicity after being given supplements or cod liver oil as an attempted preventive strategy or remedy. 
• Measles was declared officially limited in the United States in 2000—a huge public health achievement that means cases normally occur only sporadically due to travel. This outbreak threatens that achievement. If a continuous chain of infection transmission in the U.S. continues for a year, the country will lose its measles elimination status.

Neighboring countries are also grappling with large measles outbreaks. Canada’s outbreak, now centered in Ontario, originated last October with a gathering in New Brunswick and has reached 816 cases as of April 10. Mexico has reached 227 cases and began with a 9-year-old boy who traveled to Texas and back to the Mexican state of Chihuahua.

Annual measles cases and deaths, United States

What is Yale doing?

• Yale Health is monitoring the situation and is ready in case measles should emerge on campus. A collaborative team at Yale New Haven Health has developed detailed clinical pathways to support clinical care.
• See our last newsletter for more information about measles, including whether you need to get vaccinated.
• Watch an interview about the MMR vaccine with Megan Ranney, dean of the Yale School of Public Health (YSPH).
• If you’d like to take a closer look into the Southwest U.S. measles outbreak, read this data-rich brief, complete with infographics, created by YSPH students working with Joanne McGovern, an adjunct professor at YSPH.

Avian flu

Avian flu cases in humans stand at 70 confirmed and seven probable cases in the United States, with one death, unchanged since February. We have not yet seen a case of human-to-human transmission. The CDC continues to rate overall risk to the public as low, while the risk to people who may be exposed to infected animals is moderate to high. Meanwhile, the virus continues to infect poultry and dairy herds and other animals in the U.S. and around the world.

Mexico has reported its first human death from H5N1 avian flu. The affected person, a 3-year-old girl, was hospitalized in serious condition as of April 5, and died on April 8 due to respiratory complications. It is not clear yet how the child got sick or what strain was responsible.

Meningitis 

In March, a Yale student was hospitalized and treated for bacterial (meningococcal) meningitis. The student has recovered and returned to regular activities. The source of infection is unknown, which is not surprising, as some 95% of cases are sporadic.

• Thanks to speedy action by Yale Health’s clinical teams, almost all of the students and staff with whom the student was in close contact during a spring break trip were treated with a precautionary course of antibiotics within 36 hours of the initial diagnosis.
• No further cases have occurred in our community, to our knowledge.
• Incoming Yale students are nearly all vaccinated against the most common meningococcus strains, which provides good protection.

Sources you can trust  

From now on, we’ll include a suggestion or two for places to find reliable public health information. 

• A new series of fact sheets is underway from the School of Public Health. The first issues explain fluoride in drinking water and childhood vaccinations.
• You Can Know Things is a blog by Yale emergency physician Kristen Panthagani about science and clear communication “in a world of untrue facts.”

We will continue to update you on public health developments that could affect the Yale community.

In health,

Madeline S. Wilson, MD, FACP
Chief Campus Health Officer