Polio-Like Virus That Paralyzes Kids Appears to Be Making a Comeback

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A virus that can paralyze children looks to be on the rise once again. U.S. wastewater data is showing a spike in enterovirus D68, which can cause the rare, polio-like condition known as acute flaccid myelitis, or AFM. Outbreaks of AFM have followed spikes of EV-D68 in recent years, though documented cases have so far remained low in 2024.

Typically, EV-D68 causes little more than a mild respiratory infection. But over a decade ago, scientists began to notice that some children infected with the virus eventually developed AFM. The primary symptoms of AFM are sudden limb weakness, and some will also develop facial weakness, slurred speech, and pain along their limbs and back. In the most severe cases, people can develop a life-threatening paralysis that causes respiratory failure, while others may develop permanent paralysis.

EV-D68 is related to the poliovirus, which has long been known to cause a similar paralytic condition in about 0.1% of victims. And research has found that certain strains of EV-D68 have mutated to become more polio-like and more likely to cause AFM. Though there are other potential viral causes of AFM, scientists have conclusively tied the arrival of these newer strains to unprecedented outbreaks of AFM in the U.S. dating back at least 2012. While hundreds of children in the U.S. have been afflicted with AFM since then, it’s still a very rare complication of any EV-D68 infection. It now appears that EV-D68 and potentially AFM is returning to stir up trouble.

According to data collected by WastewaterSCAN, a national surveillance system testing wastewater samples run by researchers at Stanford and Emory University, the presence of EV-D68 in the country has substantially risen since early August. Since the advent of the covid-19 pandemic, wastewater data has been reliably used to provide an early warning of approaching outbreaks of infectious diseases. Historically, outbreaks of EV-D68 have tended to peak in the U.S. during the summer and fall.

“We are detecting EV-D68 nucleic acids in wastewater across the country now, and the levels are increasing,” Alexandria Boehm, program director of WastewaterSCAN and a professor of civil and environmental engineering at Stanford University, told NBC News Tuesday.

There is a curious wrinkle that’s emerged in recent years, however. Since 2012, relatively large outbreaks of AFM have appeared immediately following large outbreaks of EV-D68, which appears like clockwork every two years in the U.S. But the covid-19 pandemic interrupted the flow of many other infectious diseases, EV-D68 included, thanks largely to increased social distancing during those early years. In the summer of 2022, EV-D68 reemerged once again, but it was followed by only a muted rise in AFM, with only 47 cases documented by the Centers for Disease Control and Prevention that year (for comparison, previous outbreak years have seen between 120 and 240 cases of AFM). And so far, AFM incidence remains low this year as well, with only 13 cases to date.

It’s possible that EV-D68 has changed once again to become less likely to cause AFM, but it’s probably still too early to know for sure. Either way, experts will be keeping a close eye on the situation and continuing to study the virus. Scientists are also working to proactively neuter the threat posed by EV-D68. In June 2024, the National Institutes of Health announced that it was sponsoring a clinical trial testing out a lab-antibody against EV-D68—one intended to neutralize the virus before it can cause AFM.

It will likely take years for this treatment to reach the public, even if this and other trials go well. But in case AFM ever does become a regular threat again, having this potential preventative treatment on hand could be invaluable to many families in the future.