A new outbreak of a mysterious, potentially fatal polio-like illness could strike hundreds of American children within the next few months, U.S. health officials warned Tuesday.
Acute flaccid myelitis (AFM) outbreaks have occurred every two years in the United States since 2014, peaking between August and November, the U.S. Centers for Disease Control and Prevention said. More than 9 of 10 cases occur in children.
More than half of AFM cases wind up in intensive care, and nearly 1 in 4 require a ventilator to survive after their muscles grow too weak to adequately draw breath, according to a review of the 2018 outbreak published Aug. 4 in the CDC's Morbidity and Mortality Weekly Report.
"AFM is a medical emergency that requires immediate medical care and monitoring, as this condition can progress rapidly to respiratory failure," CDC Director Dr. Robert Redfield said. "Physicians should not delay in hospitalizing patients when they suspect AFM."
Unfortunately, this year's potential AFM outbreak will overlap with both the flu season and the continuing COVID-19 pandemic.
"We are concerned that in the midst of a COVID pandemic, cases of AFM might not be recognized or parents might be worried about taking their child to the doctor," said Dr. Thomas Clark, deputy director of the CDC's Division of Viral Diseases.
The number of confirmed cases of AFM has increased with every-other-year outbreaks -- 120 in 2014, 153 in 2016 and 238 in 2018, the CDC said.
Studies have shown that enteroviruses, and particularly enterovirus-D68, are the likely culprits behind these waves of AFM in the United States, CDC scientists said.
"We expect that AFM will likely have another peak in 2020," said Dr. Robert Glatter, an emergency physician with Lenox Hill Hospital in New York City. "That said, it's still unclear if or how COVID-19's recommended social distancing measures and attention to mask wearing and hand hygiene will impact how much enterovirus we end up seeing, along with cases of AFM."
More than 9 of 10 cases of AFM in 2018 started with a mild respiratory illness or fever consistent with a case of cold or flu. Typically, it took an average of six days before they experienced muscle weakness, researchers found.
"AFM affects the nervous system, specifically the area of the spinal cord called the gray matter," Redfield said. "Most patients develop sudden arm or leg weakness. AFM can progress quickly, and patients can become paralyzed over the course of hours or days and require a ventilator to help them breathe. Some patients will be permanently disabled."
Limb weakness occurred in 86% of the confirmed AFM cases reported between August and November of 2018. September was the worst month, with more than a third of cases cropping up then.
About half of children with AFM had difficulty walking and complained of neck or back pain, the new CDC report said. About one-third either had a fever or limb pain.
Doctors should suspect AFM in any cases of patients with sudden limb weakness, Redfield said, and parents should seek immediate medical care.
"Data confirms that non-COVID-19 ER visits dropped off sharply in 2020 due to fear of COVID-19," Glatter said. "We can assume that this trend will continue, with many people reluctant to seek care in the ER, unless we send the message to parents that time is critical, and potentially lifesaving, with AFM."
The U.S. Centers for Disease Control and Prevention has more about acute flaccid myelitis.