CDC: "Frustrated" by rare but sometimes deadly polio-like illness

The cause of a mysterious and rare polio-like illness that has infected at least 458 children since 2014, and may have killed a couple more than originally reported, is still being investigated by a Centers for Disease Control and Prevention task force.

What's new: The CDC announced Monday that acute flaccid myelitis (AFM) appears to have peaked for this year in September and October. But the task force will continue seeking the elusive cause, which has "frustrated" investigators who are stymied by not finding the same pathogen in infected patients and because cases tend to be scattered sporadically throughout the U.S.

Deaths: The CDC previously recorded only one death since the agency started surveilling the illness in 2014, but earlier this year CNN reported claims that 2 other children had died. Thomas Clark, a medical epidemiologist with the CDC, tells Axios they are investigating further that claim, but adds the agency has realized they have a "gap" in long-term followup of patients:

"This year, we are aware of no deaths in any of the cases that occurred in 2018. ... [But] we are aware of a couple of deaths this year in kids who had infections from previous years."

The task force, which should issue its first official report soon, has been testing patients for various known and unknown viruses as well as looking to see if there's any role being played by the immune response, Clark says.

• It has roughly doubled the size of its full-time staff in an effort to better track and test patients exhibiting possible AFM symptoms.

What they know: This extremely rare illness mostly infects young children, 90% of whom are reported as having had a mild respiratory illness or fever before being suddenly hit with muscle weakness or partial paralysis due to damage found in the gray area of the spinal cord.

• They've confirmed it is not caused by the poliovirus, but since symptoms are similar, it is thought it could be a similar virus.
• It has cycles of higher incidences recorded every other year, with illness reported mainly in August–October.
• Out of the 458 cases, CDC only found four with a known viral pathogen in their spinal fluid: coxsackievirus A16 and enteroviruses EV-A71 and EV-D68. (Finding a pathogen in the spinal fluid is considered offering top "proof" of the type of infection.)

Meanwhile, three scientists from the Children’s National Health System write in STAT that multiple medical centers are taking a broad look at patterns of circulating respiratory and diarrhea viruses to see if there's any spike in frequency associated with AFM.

• In addition, they've developed a research biobank for blood and spinal fluid samples.
• Children's National has also partnered with a government agency to develop cell therapy technology that they hope could someday target an exact virus to disable it.

Go deeper:

• CDC sets task force on determining cause of rise in polio-like illness
• Public health officials seek answer to mysterious polio-like illness