Experts Warn That a Deadly Disease That Causes ‘Immune Amnesia’ Is Surging in the U.S.

4 min readMeasles cases are surging in the U.S.Numbers have already surpassed last year’s cases—and we still have several months of 2026 left.Infectious disease doctors are worried about the fallout.Public health officials celebrated back in 2000 when measles was declared eliminated from the U.S. The disease was also later considered eliminated from the Americas in 2016, suggesting things were continuing to go in the right direction. But measles cases have surged in the U.S. this year (they’ve already topped last year’s numbers and we’re only halfway into 2026), which raises questions about where this is all headed.There are a lot of mixed messages out there right now about measles: Some people claim this surge in cases is no biggie; Others are sounding the alarm that this is a really serious problem. Given that measles hasn’t been a large problem in America for decades, it’s fair to be unsure what to think right now.Just know this: Doctors fall squarely into the “very concerned” camp, and for a few reasons. “Measles is not a trivial infection,” says William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine.Not only can measles be miserable to experience, but it can also cause lingering effects that can lead to everything from deafness to brain infections, Dr. Schaffner points out. Measles can even cause something known as “immune amnesia,” where your body’s immunity to a range of pathogens is basically wiped out. (More on that in a moment.)With that in mind, here’s what’s currently happening with measles in the U.S., plus why infectious disease doctors say things are getting pretty bad out there.Meet the experts: Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York; William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine; and Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health SecurityFirst, a quick recap on what measles is.Measles, which is also known as rubeola, is a very contagious viral infection, per the Centers for Disease Control and Prevention (CDC). Measles is so contagious, in fact, that up to 90 percent of people who come into contact with someone with the virus will get it if they’re not protected (like through the vaccine).Measles usually causes symptoms like a cough, runny nose, tiny spots inside the mouth, a rash, and a high fever. It can also lead to severe complications like pneumonia, immune amnesia, and encephalitis (aka swelling of the brain). “Even with uncomplicated measles, people are usually miserable for a week,” Dr. Schaffner says.About that “immune amnesia” thing…When you get measles, the virus can wipe out memory B cells and memory T cells that your immune system has built up from previous infections. “There’s a window after having measles where your immune system has taken a hit, and you have increased susceptibility to viruses, pneumonia, and diarrheal illness—it’s a real thing,” says Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York. This can last for several months, or possibly even longer, he says.What’s happening with measles right now in the U.S.?Again, measles was considered eliminated from the U.S. back in 2000, meaning the virus wasn’t considered to be spreading in the U.S. While the country did see some measles cases, they were usually in people who had visited other countries.However, cases started to slowly creep up in the U.S., with CDC data showing larger increases here and there. Things really took off last year, when 2,289 cases were reported. This year, 2,318 cases of measles have been reported so far—and there’s still a lot of 2026 left.This isn’t the highest number of cases the U.S. has seen ever, but it is the highest number of cases since measles was eliminated from the country, says Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security. “Cases were higher only in the early 1990s.”Why are cases surging?Doctors agree that lack of vaccination is the big element behind this surge. “It’s all about vaccination,” Dr. Russo says. “The anti-vaxx movement is more potent now, and they’re winning.”With fewer parents giving their children the measles, mumps, and rubella (MMR) vaccine, measles cases are creeping back up, Dr. Russo points out.And though measles has historically followed a seasonal pattern, we’re not currently in what would be considered peak measles time, Dr. Russo says. “The peaks used to be in late winter, early spring,” he says. “It’s not seasonality that’s driving cases.”As it stands now, you should expect numbers to keep going up. “At least in the short-term,” Dr. Russo says. “We’re hoping to turn that around sometime in the future.”