All 10 suspected cases are among children in northern IL.
"Despite extensive laboratory testing, we have not determined what pathogen or immune response caused the arm or leg weakness and paralysis in most patients", Messonnier added.
Most people don't even go to the doctor with a virus, and doctors rarely test patients to see which virus they have.
AFM is a rare neurological condition that affects the nervous system and spinal cord, causing sudden limb weakness or paralysis.
That's an increase of 28 cases in a matter of days. The most severe symptom is breathing trouble. Sixty-two of these cases have already been confirmed in 22 states by the CDC, with more still under investigation.
From August 2014 through September 2018, CDC has received information on a total of 386 confirmed cases of AFM across the U.S.; most of the cases have occurred in children.
"This is a mystery so far, and we haven't solved it yet, so we have to be thinking broadly", Messonnier said.
If a child "develops weakness of a limb, especially in the context of cold-like symptoms or other viral symptoms, they should see their health-care provider immediately", Toronto's Friedman told CBC. "What the physician will do is rule out other causes rule out other things that might be causing it". In the past, an oral polio vaccine could cause a polio-like syndrome in some people, but that vaccine has not been available in the USA since 2000 and the last known case in the US was in an infant with other health problems who was vaccinated in India, brought to the USA and died in 2013, the CDC says.
Officials are investigating a fifth suspected case of a potentially devastating muscle-weakening syndrome that affects mostly children and can cause paralysis, the Massachusetts Department of Health and Human Services said Monday.
Viruses, environmental toxins, and genetic disorders may play a role, CDC noted.
AFM cases on the rise in the U.S. Story continues below video.
It will take an MRI to confirm if the patients have AFM.
One linking thread is the timing, with the peak of the condition coming late in the summer and early autumn.
The CDC reports the odds of contracting AFM are less than one in a million. However, they want to stress how rare this condition is. When it infects pregnant women, the Zika virus can go into the brains of the developing fetuses and cause permanent damage. Parents can also help protect their children by encouraging hand washing, staying up to date on recommended vaccines and using insect repellent to prevent mosquito bites.