Measles on the rise and other viral updates

Key takeaways:

• What to know about measles, including prevention through vaccination.
• Respiratory viruses continue to circulate, especially seasonal flu.
• Avian flu continues to infect birds, cattle, and the occasional human. 

Measles

Measles is an airborne, highly contagious, vaccine-preventable virus. As of March 4, the measles outbreak in West Texas and New Mexico has affected 159 people, most of them unvaccinated. One person, an unvaccinated school-aged child, has died. Seven other states have reported cases, including New Jersey and New York.

To our knowledge, no measles cases have occurred this year in Connecticut, and the risk of a campus outbreak is low.

That’s largely due to vaccination. Almost all Yale students (over 99%) are immune to measles, mostly through vaccines, which results in strong community protection. But people in a few categories may consider getting a booster shot.

Here’s what you should know about measles and its prevention. 

• Famous for its rash, measles also causes high fever, red eyes (conjunctivitis), and respiratory symptoms.

• About 1 in 5 unvaccinated people with measles must be hospitalized. 
• People at higher risk for measles complications include children under age 5, adults older than age 20, pregnant women, and the immunocompromised.
• Severe complications may include pneumonia and brain swelling; about 1 to 3 of every 1000 infected children die of such complications.
• Survivors may be left blind, deaf, or with a new intellectual disability.

The measles vaccine is safe and extremely effective.

• Before the vaccine was introduced, measles resulted in 48,000 hospitalizations and up to 500 deaths in the United States every year.
• The two-dose measles vaccine, given at age 12-15 months and again at age 4-6, provides nearly complete (97%) and typically lifelong protection against infection.
• Some parents are hesitant to vaccinate their children; their concerns are often magnified by misleading claims on social media. In fact, the risks of serious measles infection—hospitalization, pneumonia, brain swelling, long-term complications—far exceed the risk of vaccination.

Should adults get measles boosters?

For most, it’s unnecessary. The following people are considered immune and do NOT need boosters:

• People born before 1957.
• Those with a history of measles as a child.
• Those with documentation of 2 doses of vaccine 28 days apart or with documented positive serology.

The following people could consider a booster dose of the measles/mumps/rubella (MMR) vaccine through a healthcare provider. If needed, a booster is safe regardless of prior vaccination:

• Those who are unsure of their vaccination status (do try to find those old records).
• Those vaccinated between 1957 and 1968, when an ineffective vaccine was in use.
• Those unsure of vaccination status or at increased risk due to immune compromise who must travel to western Texas or another area where there is an active outbreak (such travel should be avoided if possible).
• Infants in families traveling to an outbreak setting or internationally, who may be vaccinated as early as 6 months of age.

People who have never been vaccinated should get two vaccine doses at least 28 days apart. Note that a small group should not be vaccinated with MMR: those with a documented allergy, with severe immune compromise, or women who are pregnant.

Coughs are still in season

Respiratory viruses—especially flu—continue to sicken Americans. Both the nation and Connecticut are still seeing high levels of emergency visits for influenza, but numbers are finally trending down. Yale Health saw a peak in February, when nearly half of samples were positive for flu; last week, 19% of samples tested positive for flu, compared with 6.3% for respiratory syncytial virus (RSV) and only 1.6% for COVID. Of note, we are seeing an increase in influenza B at 9.5% positivity, which commonly happens late in the season.

This flu season was the worst since 2017-2018, with 480,000 hospitalizations and 21,000 deaths. While rates are now decreasing, the Centers for Disease Control and Prevention (CDC) expects several more weeks of flu activity.

Vaccines 

It’s not too late.  Vaccines are still available through the Yale Health Immunization Department for Yale Health members and students (self-schedule through MyChart) or through your healthcare provider.

• The COVID vaccine is still likely to be beneficial if you have not yet had this season’s vaccine.  Those aged 65 or older or immunocompromised should get a second dose of the COVID vaccine 6 months after the first dose.
• The flu vaccine is recommended as long as the virus continues to circulate.
• RSV vaccine is recommended for adults over age 75, younger adults with certain medical conditions, as well as for infants and pregnant women.

Avian flu (H5N1)

Avian influenza (a.k.a. bird flu) continues to infect wild animals and livestock around the country. In Connecticut, wild birds in multiple counties have been affected. Backyard flocks in our state have experienced two outbreaks in New London County and one in New Haven County so far this year. New developments since my last message:

• Up to now, the strain affecting cattle (B3.13) has been the same since the start of this outbreak in spring 2024, indicating a common source from a spillover shortly before.
• However, a new spillover of virus from birds to cattle has now occurred. It involves a more severe strain called D1.1 that has been infecting poultry and wild birds and some people—the same strain that resulted in the death of a Louisiana man early this year after he had contact with sick birds.
• The D1.1 strain has now been identified in dairy herds in Nevada and Arizona. This suggests that, amid so much infection in birds, we may see continued “seeding” of H5N1 infection in dairy herds, making it harder to control.

Human cases 

As of February 28, the CDC has reported 70 confirmed and 7 probable cases of avian flu in humans, with one death. Most of these patients had documented contact with infected animals, and most experienced mild illness.

What is the risk of more human cases?

Despite the ongoing outbreak in animals and cases in humans, the CDC continues to rate the risk to the general public as low. However, the risk to those in contact with potentially infected animals or contaminated surfaces or fluids is rated as moderate to high.

Below is a helpful graphic describing scenarios that may increase general population risk, with thanks to epidemiologist Katelyn Jetelina of Your Local Epidemiologist, adjunct professor at Yale School of Public Health. (Note that infection in pigs is concerning because they have been shown to be a perfect “mixing vessel” for influenza viruses, providing opportunity for genetic reassortments that would increase risk to humans.)

What should you be doing now? 

• Those with backyard flocks should take precautions, watch for sick birds, and notify the Connecticut Department of Agriculture if concerns arise.
• Hunters, agricultural workers, and others should avoid handling dead birds.
• Avoid drinking raw milk, which may contain avian flu viruses. These viruses are inactivated by pasteurization. (To date, no human cases have been directly linked to raw milk.)

Don’t feed your pets food containing raw animal products and keep them from eating dead birds. The American Veterinary Medical Association has information regarding pets and backyard flocks.

We will continue to update you on infectious diseases and other developments that could affect the health of the Yale community.

In health,

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