The U.S. Centers for Disease Control and Prevention is warning parents about a rare disease known as acute flaccid myelitis (AFM), a polio-like “mystery illness” that may cause arm or leg weakness and paralysis, particularly in children.
AFM remains an extremely rare condition, but it is a serious disease that affects the nervous system and results in polio-like symptoms that can carry long-term effects, the CDC says. It affects a person’s nervous system, specifically the spinal cord, causing weakness in one or more limbs. AFM or neurologic conditions like it have a variety of causes such as viruses, environmental toxins, and genetic disorders, the CDC says.
In 2018, so far, the CDC has received reports of 127 patients under investigation (PUIs), with 62 cases confirmed as AFM in 22 states. The states were not disclosed. The CDC, along with state and local health departments, are investigating some of these PUIs.
Of the confirmed cases, the average age is about 4 years old. More than 90 percent of the cases are in children age 18 years and younger. One death of a child diagnosed with AFM occurred in 2017.
Symptoms of AFM include:
- Difficulty moving the eyes or drooping of eyelids;
- Facial droop or weakness;
- Difficulty with swallowing or slurred speech;
- Sudden arm or leg weakness.
“This illness is very rare, but if parents have concerns regarding these symptoms in their child, they should take them to a pediatric emergency room,” said Fernando Mendoza, M.D. , medical director of the Children’s Emergency Center  at Baptist Children’s Hospital  and associate medical director of Pediatric Emergency Services at West Kendall Baptist Hospital. “Pediatric ERs are better suited to handle neurological cases such as AFM and other conditions affecting children.”
During a press briefing Tuesday, CDC officials expressed frustration. While the symptoms can mimic those of polio, CDC officials say AFM has tested negative for the poliovirus. Polio was a crippling disease until it was eliminated in the U.S. following the introduction of the polio vaccine in the 1950s. The CDC received reports of 33 confirmed cases of AFM across 16 states in 2017. That’s down from 149 confirmed cases in 39 states in 2016. In total, there have been 386 confirmed cases since 2014, the first year the CDC began chronicling AFM.
“We don’t know which viruses are predominantly causing AFM,” says Dr. Mendoza. “There is ongoing close surveillance around the country, with ER physicians instructed to identify potential AFM cases. The best way to protect your child from diseases is to maintain a normal vaccination schedules and practice good hygiene habits.”
The CDC states that AFM can be caused by other viruses, such as enterovirus  and West Nile virus , environmental toxins and a condition where the body’s immune system attacks and destroys body tissue that it mistakes for foreign material, the CDC stated.
“While we know that these can cause AFM, we have not been able to find a cause for the majority of these AFM cases,” said Nancy Messonnier, M.D., director of the CDC’s National Center for Immunization and Respiratory Diseases, during the media teleconference. “The reason why we don’t know about AFM — and I am frustrated that despite all of our efforts we haven’t been able to identify the cause of this mystery illness — we continue to investigate to better understand the clinical picture of AFM cases, risk factors and possible causes of the increase in cases.”
While cases of AFM arise mainly in August and September, and there has been a spike this year, Dr. Messonnier emphasized that the disease is “incredibly rare.”
Overall, the rate of AFM since 2014 is less than one in a million. Nonetheless, CDC officials understand how concerning this can be for parents, so the agency is providing weekly updates on its website page dedicated to AFM .