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Measles cases are spreading across the country.
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Doctors tell you what to do if you have been exposed to the virus.
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Plus, what infectious diseases doctors want you to know about the disease.
Public health officials in New Jersey, Massachusetts and Colorado recently sent out warnings about measles-infected travelers passing through busy airports and other areas. Combine that with measles’ ability to spread quickly, and it’s understandable to have concerns about the disease.
“Measles is extraordinarily contagious—if you’re susceptible,” says Thomas Russo, MD, professor and chief of infectious diseases at the University of Buffalo in New York.
Each year, a small number of measles cases occur in certain areas of the country. But the last 12 months have been different. Nearly 2,100 people in 44 states were affected by measles in 2025, according to data shared by the Centers for Disease Control and Prevention (CDC). This is the highest number of cases in the last 25 years. Unfortunately, cases continue to emerge.
Meet the experts: John Sellick, DO, infectious disease expert and professor of medicine at the State University of New York at Buffalo; Amesh A. Adalja, MD, infectious disease expert and senior research fellow at the Johns Hopkins Center for Health Security; Thomas Russo, MD, professor and chief of infectious diseases at the University of Buffalo in New York.
These exposure warnings keep coming, which makes it fair to wonder what this means for you. Here, infectious disease doctors break down some of the most pressing questions people have about measles, plus what to do if you’re exposed.
Why is measles so contagious?
Although there are outbreaks across the country every year, most people are not very familiar with measles. Also known as rubella, measles is a highly contagious respiratory virus, according to the CDC. It can cause symptoms such as coughing, runny nose, red and watery eyes, high fever and spots inside the mouth.
But measles can also cause serious health complications, including pneumonia and encephalitis (inflammation of the brain), according to the CDC.
Measles is considered one of the most contagious diseases in the world, according to the World Health Organization (WHO). The virus can remain active and contagious in the air or on infected surfaces for up to two hours. The WHO also notes that one person who is infected with measles can infect up to 18 other people.
The virus spreads when an infected person coughs or sneezes, Dr. Russo explains. From there, people breathe in infectious particles or touch surfaces on which those particles land and then touch their eyes, nose, or mouth, which can lead to infection.
The infectious period with measles is long – people who are infected can spread the virus to others four days before developing the classic measles rash and four days after it appears, according to the WHO.
How can I prevent measles?
There is a vaccine to prevent measles called the measles, mumps and rubella (MMR) vaccine. It is part of the childhood vaccination series and is administered in two doses. One dose is 93 percent effective in preventing measles, while two doses are 97 percent effective, according to the CDC. (Despite new changes to the CDC’s childhood vaccination schedule, the MMR vaccine is still recommended for all children.)
The first dose is usually given between 12 and 15 months, and the second dose is given between four and six years or whenever children start school, according to the American Academy of Pediatrics (AAP). It’s still possible to get the MMR vaccine as an adult or beyond that age range, but doses must be spread out over 28 days, according to the AAP.
The MMR vaccine is a live attenuated vaccine, meaning it contains a weakened form of the measles virus, explains John Sellick, DO, an infectious disease expert and professor of medicine at the State University of New York at Buffalo. That trains your immune system to react if you’re exposed to measles on the road.
“The vaccine isn’t perfect, but it’s very good,” says Dr. Russo.
(Be aware that people born between 1963 and 1967 received a measles vaccine during childhood that is not considered effective, according to the CDC. If this describes you, the CDC recommends getting vaccinated again.)
Finally, you can get measles if you are fully vaccinated, but it is unlikely. (Again, the vaccine is 97 percent effective, so three out of 100 people vaccinated can get it.) “There were a few people who got a vaccination in the most recent measles outbreak and got infected,” says Dr. Russo. “But if you have some protection, you’re less likely to get severe disease.”
What to do if you have been exposed to measles
If you discover that you have crossed paths with someone who has measles, do not panic. If you were born before 1957, doctors consider you to have “presumed immunity,” meaning you were probably exposed to the virus as a child and therefore should be immune to it, Dr. Russo says. “If you have presumptive immunity or if you’ve been vaccinated, you don’t have to worry about exposure to measles,” he says.
Amesh A. Adalja, MD, an infectious disease expert and senior research fellow at the Johns Hopkins Center for Health Security, agrees. “There is no action to be taken,” he says.
If you were born after 1957 and have not been vaccinated or are partially vaccinated, you still have options. While there’s no cure for measles, you can get vaccinated after exposure or get an injection of antibodies called serum immunoglobulin to help protect against severe disease, Dr. Adalja says. (Immunoglobulin serum treatment is the only option for pregnant women, infants, and people who are immunocompromised because the vaccine is a live virus and is not recommended for those groups, Dr. Russo explains.)
But if you know you’ve been exposed and aren’t sure if you’re immune, “the safest thing to do is get vaccinated,” says Dr. Russo. Dr. Sellick agrees. “It’s safe to get another dose even if you’ve been fully vaccinated or already immune to the virus,” he says.
What to do if you get measles
If you develop symptoms of measles, call your doctor (don’t go into the doctor’s office – you risk exposing others). Again, there is no cure for measles, but your doctor may suggest serum immunoglobulins and supportive care, such as acetaminophen for fever and plenty of fluids, along with monitoring you for serious complications of the virus. Finally, it is best to contact a healthcare provider. They can provide next steps from there.
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