Measles is spreading. Here’s what experts say you should know

As measles cases surge in the United States, leading to the country’s first two measles-related deaths in a decade, questions, worries and misinformation about the infectious disease are swirling. More than 300 confirmed measles cases have been reported this year as of March 13, largely associated with an outbreak at the border between Texas and New Mexico, according to the U.S. Centers for Disease Control and Prevention. Unvaccinated children make up the majority of confirmed cases. 

Still, the number of deaths “suggests that the outbreak is much bigger than the official number,” says infectious diseases physician Peter Chin-Hong of the University of California, San Francisco. Based on the expected fatality rate of 1 to 2 people per 1,000 infections, he says, the real number of cases may be closer to the high hundreds if not over 1,000.

Known for its blotchy red rash that usually starts on the face, measles can lead to high fever, pneumonia, ear infection and brain swelling. The virus that causes measles is highly contagious. The airborne virus spreads when an individual comes in contact with someone who’s sick or with virus-contaminated surfaces. It can linger in the air for hours even after an infected person has left the room. After exposure, up to 90 percent of people without immunity to measles will catch it. 

Vaccination is the best way to gain protection, health experts say. But measles vaccination rates among kindergarteners have dropped from 95.2 percent in the 2019–2020 school year to 92.7 percent in 2023–2024, leaving around 280,000 kindergarteners vulnerable that academic year, according to CDC. The decline preceded new scrutiny of the childhood vaccine schedule by U.S. Health and Human Services Secretary Robert F. Kennedy Jr., a known vaccine skeptic. 

The measles vaccine “not only prevents serious disease, it also prevents infection,” Chin-Hong says. “It’s a fantastic vaccine.” 

Since the United States first declared measles eliminated in 2000, the country has rarely exceeded 300 cases within a year. Most outbreaks and isolated cases are sparked by travelers bringing the virus from places where it circulates more widely.

But the early uptick in 2025 now has left many people wondering whether they need a booster shot, what the early warning signs of measles are and how to treat it. To learn more, Science News spoke with several physicians and researchers well-versed in infectious diseases. 

What are the early signs and symptoms of measles?

Generally, it starts with a fever, cough, runny nose and red eyes, Chin-Hong says. But the early symptoms resemble those associated with plenty of other illnesses, leaving measles to be dismissed as something like a simple cold. 

“Nobody really knows it’s measles in the beginning,” Chin-Hong says. “That’s why it’s so insidious and could be so transmissible.” 

Around three to five days later, however, a telltale rash usually appears. It typically starts on the face and works its way down the body. But people are infectious up to four days before the rash appears, and four days after, Chin-Hong notes. An infected person may not show symptoms until up to three weeks after picking up the virus.

Can good nutrition protect you from getting measles or having a bad outcome after contracting it? 

No. 

“Nutrition is no substitute for vaccination,” says Scott Weaver, who directs the Institute for Human Infections and Immunity at the University of Texas Medical Branch in Galveston. “There’s no evidence anywhere in the world that it prevents infection or that it prevents the spread from infected people to others.… The main way to stop this outbreak is through vaccination. There’s no reason to think that improving nutrition is going to have any impact on the trajectory of this outbreak.”

“Nutrition is no substitute for vaccination.”

Scott Weaver, University of Texas Medical Branch in Galveston 

Measles doesn’t pass over the well-nourished, agrees Larry Kociolek, an infectious diseases pediatrician at Ann & Robert H. Lurie Children’s Hospital of Chicago and Northwestern University Feinberg School of Medicine. “The frightening thing about measles is how contagious it is in the air. If you enter the room of somebody with measles — even if that person left that room an hour or two prior — if you’re not immune to measles, you can catch measles.

“Your risk of acquiring measles is not going to go down if you’re not immune just because you’ve otherwise lived a healthy lifestyle.”

But children who are malnourished have a greater chance of catching diseases and may develop more severe disease than kids with adequate nutrition.Severe malnutrition is not usually involved in measles outbreaks in high-income countries like the United States.

Do antibiotics, vitamin A or cod liver oil help treat measles?

Not directly, Weaver says. “A lot of the severe infections progress to [pneumonia, which] can be caused by bacteria, and in this case, they certainly need antibiotics.”

As for supplements, “the reason that this is in the news is that there were studies in Africa and Asia that showed one of them, vitamin A supplements, actually increased survival among children,” he says.

That may be because children in those parts of the world have a greater likelihood of being vitamin A deficient, Kociolek says. “If you’re vitamin A deficient and you get measles, it is very important that you get vitamin A as a treatment to reduce the severity of disease. But there’s no evidence that if you’re not vitamin A deficient, that vitamin A provides any benefit.” 

In fact, taking too much vitamin A can be dangerous, he says. Symptoms of vitamin A toxicity include nausea, vomiting, liver damage, hair loss and brittle bones that can lead to fractures.

Unfortunately, “there’s no treatment for measles,” Chin-Hong says. When someone is hospitalized with severe disease — usually an infant — doctors may give them a general antiviral drug called ribavirin that’s sometimes used to treat hepatitis C and RSV. “There’s no great data” for ribavirin helping with measles, he says, but it’s used occasionally because there are no measles-specific drugs.

Does getting measles strengthen your immune system in the long run? 

No. In fact, the opposite, Weaver says. “It actually interferes with your immune system in the short run. If you’re infected by a [measles] virus without being vaccinated, the infection suppresses your immune response for typically a few months to a few years, and that can lead to you being more vulnerable to secondary infections.”

Measles can also cause long-term damage to the immune system. After an infection or vaccination, immune cells known as T cells, B cells and plasma cells maintain the memory of those invaders, says Stephen Elledge, an immunologist at Brigham and Women’s Hospital in Boston. “B cells are involved in making antibodies. They actually don’t secrete antibodies. They differentiate into these plasma cells, and the plasma cells become the antibody factories. They go to your bone marrow, and that’s where they stay for the rest of your life.They can live for 30 [to] 40 years, the whole time just pumping out the memory of your infections,” he says. “It turns out that measles can kill those cells.… It kills the T cells and kills the B cells. It kills the plasma cells.” 

So 10 to 20 percent of people infected with measles have the immune memory of other infections or vaccinations wiped out, Elledge says. That may leave them vulnerable to illnesses in the future even if they were previously infected or vaccinated against bacteria and viruses. 

“We showed it happens in people and in controlled experiments with macaques, so it’s undeniably true. And the epidemiology backs it up 100 percent,” Elledge says. 

The vaccine is a weakened virus that does not kill the immune memory cells so it can’t cause immune amnesia. Instead it guards against measles and other infectious diseases by shielding the immune system’s memory. 

“Natural immunity” from infections also carries risks far beyond those associated with vaccination. “This natural immunity theory is dangerous,” Kociolek says. “The natural infection for measles can be severe. [About] 20 percent of children will require hospitalization for measles, a small percentage will get life threatening brain swelling. There’s a small proportion of people who will recover and be seemingly fine, and then several years later, sometimes 10 to 20 years later, will get lethal inflammation of the brain from their prior infection.” By contrast, “the measles vaccine is incredibly safe.”

What’s the recommended age for babies and children to get the measles vaccine?

Usually infants get a measles vaccine when they are about a year old and a second shot when they are 4 to 6 years old. But in the Texas outbreak area, the state health department is advising parents to get babies vaccinated when they are as young as 6 months old. That early shot should be followed with the regular schedule of measles vaccines.

The reason doctors typically hold the first measles shot until a child turns 1 year old is that antibodies from the mother protect the baby and may interfere with the vaccine. “Those antibodies prevent the vaccine from replicating well,” Weaver says. “But if the mother was not vaccinated or infected and that baby has no immunity, then it’s a good idea to give them the vaccine earlier.” 

Can you get measles as an adult if you’ve had it before or were vaccinated as a child?

“Very unlikely,” Weaver says. “The vaccine with two doses protects about 97 percent of people from getting measles again, and natural infection is probably a similar level of protection.”

Even if you do get it, you’ll probably have a milder disease, Chin-Hong says. 

Does immunity from the measles vaccine wane over time?

Probably somewhat, says Elledge. “Antibodies [against the measles virus] stick around a long time … but they do go down. They’re really good when you’re young, and then they start dropping off.” 

Older people who were vaccinated many decades ago may have lost some protection, he says.

“The idea that it gives you lifelong protection may be true, but it probably would be more true if you were in an environment where you occasionally got reinfected.” Occasional exposure to the virus or vaccine booster shots may help build stronger immunity, he says. 

But, Weaver says, “the majority of people don’t need to worry about it. There’s very little evidence of people with older age losing the protection against the infection. So unless they have some particular circumstance [such as] their immunity might wane because of some general immune deficiency, then they can get tested for their antibody levels. The vast majority of people [who] receive two doses as a child, they should be protected for life.”

Should adults get a booster shot? 

Some should, Kociolek says. “In general, if you’ve had one dose of vaccine you’re protected, probably with 93 percent effectiveness. If you’ve had two doses of vaccine you’re about 97 percent protected as well. So that’s considered adequate immunity. 

“Those who have had a prior measles infection are protected lifelong,” he adds. “Individuals who were born in the United States before the year 1957 are also considered immune. That was before vaccination, [but measles is] so transmissible that everyone born in the U.S. before 1957 is thought to have had measles. If those criteria don’t apply to you, you may need to be vaccinated.”

Is there a way to find out if you should get a measles shot?

Ideally, Weaver says, people “would go to their health care provider who would have complete records of their vaccination and find out if they received two doses as a child. [If so] they really don’t need to be vaccinated again. If those records are not available and they’re relying on their own memory or what they were told by their parents and they’re not certain about that, it’s certainly a good idea to get a booster, even if they likely were vaccinated as a child. It really can’t hurt to get that booster.”

Health care workers may “get boosted if their antibodies have dropped below a certain threshold. But for the vast majority of people, they don’t really need to worry about that if they’re pretty certain they’ve been vaccinated as a child.”