CDC: Cases of polio-like illness rise nationwide

Cases of a rare polio-like illness that mostly affects children have jumped nationwide since last month, and federal health officials said Tuesday they have not been able to determine a single cause of the mysterious condition or explain why it primarily occurs in two-year cycles.

The federal Centers for Disease Control and Prevention has confirmed 90 cases of acute flaccid myelitis, or AFM, across the United States and is investigating 252 suspected instances of the disease — an increase from 127 suspected cases on Oct. 16, officials said.

AFM tends to develop within three to 10 days of a common cold or mild flu-like symptoms. While the affliction mainly strikes children, a few adults have been diagnosed, experts said.

Illnesses occur from late summer through early winter and can affect one or more extremities. Patients lose muscle tone and reflexes, and an arm or a leg can become paralyzed.

Most of the children whose cases were confirmed are between the ages of 2 and 8, said Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, a division of the CDC.

Nine suspected cases of AFM are being investigated in New York, but there have been no confirmed cases of the rare disease, a spokeswoman for the state Department of Health said Tuesday.

"This is an extraordinarily rare condition," said Dr. Sophia Jan, division chief of general pediatrics at Cohen Children's Medical Center in New Hyde Park. "Millions of children get colds every year, but there have been only 90 confirmed cases of AFM [nationwide]."

Parents should not worry if a child catches a cold, though any sign of weakness in an extremity warrants an immediate visit to the nearest emergency room, Jan said.

"We don't have a good understanding of what's causing AFM. We suspect there might be certain viruses, combined with some children having a genetic predisposition," she said.

While the CDC has been documenting cases of the illness for years — it first was diagnosed in 1968 — agency experts said AFM is largely a mystery. Cases often crop up in two-year cycles, but sometimes occur more frequently.

"One of the gaps in our program is that we don’t have long-term follow-up on these cases," said Messonnier, referring to children who were diagnosed in 2014 and 2016, as well as earlier.

During a telephone news briefing Tuesday, Messonnier said medical experts have a number of theories about an underlying culprit. But to date, no one has been able to nail down a cause. There have been no deaths, she said.

In tests of spinal fluid, some children have had evidence of a type of pathogen known as an enterovirus. Doctors have identified two different ones: EV-D68 and EV-A71. Messonnier said EV-D68 was more prevalent in 2014, but less so this year.

For many who have been diagnosed, there have been no signs of viral infection at all, she said.

“We’re not sure if the reason we are not finding a pathogen in all cases is because it has cleared, or because it is hiding,” she said, alluding to the possibility that an infectious agent may secure safe harbor somewhere in the body, allowing it to remain undetected.

“Even in patients where we are finding a pathogen, we are not certain whether the pathogen is the cause,” Messonnier said.

The disease could be caused by an autoimmune response, which means the body attacks itself, damaging nerves that control the extremities.

Because of the many questions, Messonnier said a task force of medical experts is being formed to expand scientific understanding of the seasonal affliction. AFM can have long-term consequences; some children have experienced persistent weakness.

The Association of State and Territorial Health Officials, a nonprofit representing public health agencies in the United States and its territories, is expected to ask federal health authorities to declare AFM a reportable disease, a designation that would put it on par with other serious infectious disorders.

Having that designation would require mandatory tabulation of cases and strict definition of the affliction. Other reportable diseases include measles, mumps, Legionnaires' disease, and certain hospital-acquired bacteria.

“As a mom, I can certainly understand why parents are worried,” Messonnier said. "I am worried about the increase in AFM. It is a very rare condition."