The Illinois Department of Public Health is investigating nine recent cases of acute flaccid myelitis, also called AFM, according to a statement Wednesday.
All of the cases are in patients younger than 18 and have been clinically diagnosed by health care providers, the statement said. State health officials are working with the care providers to obtain the samples and information to send to the US Centers for Disease and Prevention for testing and confirmation of the diagnoses.
"The CDC will make the final determination on diagnoses and numbers are subject to change," the statement said.
All of the patients are "from northern Illinois," according to the health department, but no other location information was provided.
Since 2015, when Illinois began monitoring reports of AFM in the state, four confirmed cases have been identified.
AFM is a polio-like illness that affects a person's nervous system, including the spinal cord. Symptoms can include sudden limb weakness, loss of muscle tone and reflexes, facial and eyelid drooping, facial weakness, difficulty moving the eyes, swallowing difficulty or slurred speech, according to the CDC.
The rare condition can be caused by a virus, a genetic disorder and environmental toxins.
There is no treatment other than managing each patient's symptoms.
Dr. Rachel Herlihy, the Colorado state epidemiologist, said the best prevention is frequent handwashing and keeping kids home when they are sick.
On Tuesday, the Colorado Department of Health said it has confirmed 14 cases there this year. All of the patients are children who have needed to be hospitalized, the department said, noting that "nearly all have fully recovered."
"The state health department has been monitoring this situation closely since early spring. In addition to investigating the outbreak, the state health department has issued alerts to health care providers on how to test for the viruses and enhanced guidance to child care centers on infection prevention," the department said in a statement.
The type of viruses found in 12 of the Colorado cases, enterovirus, typically increases in summer and fall and is common, the state department of health said. However, 11 of the Colorado cases of AFM have tested positive for EV A71, a rare type of enterovirus not usually seen in the US, rather in Asia and other parts of the world, according to Herlihy. "This is certainly the largest outbreak of enterovirus A71 we've seen in Colorado."
She referred to these 11 cases as an outbreak within an outbreak. "We have 41 cases of children who have had some sort of illness of enterovirus A71, which is causing a wide spectrum of neurological illness."
In previous years, cases of AFM in Colorado and elsewhere have been positive for a different enterovirus, EV-D68.
On Friday, the Minnesota Department of Health said it was investigating six cases of AFM in children over the past few weeks but did not identify what virus or other cause may have led to the illnesses.
As of September 30, according to the CDC, 38 cases of AFM have been confirmed in 16 states. This does not include all of the 14 cases announced by Colorado, as some of those cases were confirmed after September 30. It also does not include the cases in Minnesota or Illinois, as they are not confirmed.
Since August 2014, when the CDC began tracking the illness more closely, the agency has reported 362 cases.
In 2017, 33 cases were reported in 16 states. One hundred forty-nine cases were reported in 39 states in 2016 and 22 cases in 17 states in 2015.