Measles has made an unwelcome return to the U.S., with dozens of children across multiple states having caught the highly contagious viral disease so far this year. There are several reasons why measles has become a larger problem both here and worldwide as of late, but there’s one commonly speculated suspect for its resurgence that simply isn’t to blame: covid-19.
As of early April, according to the Centers for Disease Control and Prevention, there have been 113 measles cases detected in 18 states, with the most reported in Illinois. Two-thirds of the cases have involved children, and half involve children under the age of 5. No deaths have been reported, but 65 people have been hospitalized for isolation or to manage complications of the infection, including 37 children under 5.
Measles was locally eliminated in the U.S in 2000, meaning that cases of measles seen in the country today usually originate from somewhere else. But outbreaks can and do sometimes spread here. Some of the seven ongoing outbreaks in the U.S. date back to late last year, but the tally of cases is already double the toll reported in 2023 and is on track to be the most seen in a year since 2019, which saw over 1,200 cases.
If you browse social media posts discussing these outbreaks, it won’t take long to see people point to covid-19 as a culprit. Some people argue that, since covid is known to weaken people’s immune systems, it must have provided fertile ground for measles to emerge once again. It isn’t just measles either—similar arguments have been made to explain the recent uptick of tuberculosis or unusual outbreaks of disease, like the clusters of severe pediatric hepatitis cases that occurred across several countries in 2022. And some people have even gone as far as to nickname covid “airborne AIDS”—invoking the well-known effects of an untreated HIV infection in causing other opportunistic infections.
The biggest problem with this hypothesis, at least for measles specifically, is that there isn’t really a need to come up with a special explanation for its return. The measles virus can spread incredibly well between people who haven’t been exposed to it previously. So as long as there are large enough pockets of people not immune to measles in a community, it will always have the chance to cause wildfires of disease once given the opportunity. Measles also remains endemic in many parts of the world, so there’s no shortage of sources for new outbreaks.
“There were measles outbreaks among unvaccinated people long before covid-19,” Emily Smith, an epidemiologist specializing in infectious diseases at George Washington University’s Milken Institute School of Public Health, said in an email to Gizmodo.
All states mandate vaccination against measles and other once-common germs before children enter the public school system. And while the national rate of childhood measles vaccination is still high—93.1% in the 2022-2023 school year—it’s recently dipped below the 95% threshold that experts say is needed to ensure limited spread in a community (a concept known as herd immunity). Some regions of the U.S. have even lower vaccination rates, giving measles that much more room to spread if it’s ever introduced there.
There’s nothing strange going on with these latest outbreaks, immunity-wise. According to the CDC, 83% of cases have involved people who were either unvaccinated or have an unknown vaccination status, while another 12% of cases involved people who only received one of the two vaccine shots needed for measles. Measles vaccination is highly effective and long-lived (upwards of 99% protection with the full two shots), but it isn’t completely foolproof, so the occasional case in vaccinated people can occur, especially if the virus is allowed to circulate in a community long enough.
The other stumbling block here is that there’s simply not much supporting the idea that covid is eroding our defenses to other germs on a widespread level.
“There’s no evidence that covid—or the vaccine—is adversely affecting people’s immune systems,” Richard Rupp, a pediatrician and the director of clinical research at the University of Texas Medical Branch’s Sealy Institute for Vaccine Sciences, told Gizmodo. “Measles has always been worrisome. I think people have this image of measles as just red spots on the face, or someone being a sad sack sitting there with it. But no, it’s always been a bad disease.”
Life-threatening cases of acute covid are known to wreak havoc on the immune system, and they can raise a person’s risk of catching other germs at the same time, though this is true of any severe infection. Some people can also experience lingering symptoms after their initial covid infection (including mild ones), a condition known as long covid. And there is evidence suggesting that at least a subset of long covid cases could be tied to ongoing, harmful changes in the immune system triggered by the infection.
But even these changes seem to be examples of immune dysregulation and overactivation, not the sort of long-term immune deficiency that could make someone more susceptible to other infections (something that does happen with HIV). On a population level, there is no data showing that rates of known opportunistic infections have exploded the way you would expect if covid was weakening everyone’s immune systems. And much like these latest measles outbreaks, covid is hardly needed to explain every mysterious cluster of illness that shows up. The strange wave of severe child hepatitis cases that occurred in 2022, for instance? It now appears to have been caused by a previously unknown interaction between a common virus and a rare genetic vulnerability to severe infection from it.
To put it bluntly, there is no good reason that covid should be viewed as “airborne AIDS.” And it does a disservice to everyone to treat it as such. Covid remains a real public health issue (it killed at least 48,000 Americans last year, according to provisional CDC data), and those with long covid deserve more attention and research. But blaming every other health problem on the coronavirus is both inaccurate and a wasteful distraction.
The pandemic did have a real effect on the return of measles globally, for instance, since it interrupted or diverted resources from existing measles vaccination programs, especially in poorer countries. The disinformation spread by the anti-vaccination movement about the covid-19 vaccine also likely weakened public confidence in other vaccines. So beating back measles will require reminding people everywhere about the value of vaccination and ensuring that they can easily access vaccines.