Active Resurgence

Measles Tracker 2026

United States · CDC-reported confirmed cases and outbreaks

Source: CDC Measles Cases and Outbreaks. Not a medical authority. Verify with CDC.

About Measles

Incubation period

7 – 21 days after exposure

Contagious period

4 days before to 4 days after rash appears

Airborne survival time

Up to 2 hours in a room

Vaccine effectiveness (2 doses MMR)

~97%

What is measles?
Measles is a highly contagious viral disease that was declared eliminated in the United States in 2000, meaning it no longer spread continuously here. It has since returned through travelers bringing the virus from countries where it still circulates, and it spreads quickly in communities with lower vaccination rates. Most of the cases reported each year are linked to a smaller number of outbreaks rather than being spread evenly across the country.

How does it spread?
Measles is one of the most contagious diseases known. It spreads through the air when an infected person breathes, coughs, or sneezes, and the virus can stay infectious in the air or on surfaces for up to two hours after that person has left a room. About 9 out of 10 unvaccinated people who are exposed to someone with measles will become infected themselves.

What are the symptoms?
Symptoms usually start 7 to 21 days after exposure with high fever, cough, runny nose, and red, watery eyes. A few days later, a rash of flat red spots typically appears on the face and spreads down to the rest of the body. People are contagious for about four days before the rash appears through four days after, often before they know they are sick.

Why does it matter beyond the rash?
About 1 in 5 unvaccinated people who get measles in the US are hospitalized. Complications can include pneumonia, encephalitis (swelling of the brain), and in rare cases death. Measles infection can also temporarily weaken the immune system afterward, making it harder to fight off other infections for some time.

Who is most at risk?
Children under 5, adults over 20, pregnant people, and anyone with a weakened immune system are most likely to develop severe complications. The people most at risk of catching measles at all are those who are unvaccinated, including infants too young for their first MMR dose and people who have chosen not to vaccinate.

How to protect yourself and others

•Make sure you and your children are up to date on the MMR (measles, mumps, rubella) vaccine. Two doses are about 97% effective at preventing measles.

•If you think you or your child has measles, call a healthcare provider before visiting in person so they can take precautions to avoid exposing others.

•If you are not immune and have been exposed, contact a healthcare provider promptly. A vaccine dose or other treatment given soon after exposure can sometimes prevent or lessen illness.

•Check vaccination requirements before international travel. Most measles cases in the US are linked to unvaccinated travelers returning from areas with ongoing transmission.

•If you are sick, stay home from work, school, or childcare until at least 4 days after the rash appears to avoid spreading it to others.

Why is 2026 different?
2026 case counts are tracking close to 2025's totals well before the year is over, and the vast majority of cases are tied to a relatively small number of outbreaks rather than isolated travel cases. This pattern, concentrated outbreaks driving most of the national total, is the hallmark of measles spreading in communities with vaccination gaps once it gets a foothold, rather than broad nationwide circulation.

Sources: CDC Measles Cases and Outbreaks · CDC About Measles · CDC Measles Vaccination