Forty-two states and the District of Columbia now have a total of 500 confirmed cases of Enterovirus D68, the severe respiratory illness that has been infecting children since the summer, US health officials reported Wednesday. Four people infected with the virus have died in recent weeks, but it’s not clear what role — if any — the virus played in those deaths, officials said.

Health officials are also trying to determine if the virus is associated with cases of muscle weakness and even paralysis that have struck 10 children in the Denver area. Other cases of muscle weakness or paralysis have been reported in Massachusetts, Michigan, and Missouri, according to The New York Times. Doctors don’t know if the limb weakness or paralysis is temporary or will be long-lasting — or whether it has anything to do with Enterovirus D68.

Among the mortalities was a 10-year-old Rhode Island girl who died last week, Rhode Island and federal health officials said Wednesday. Her death was caused by a bacterial infection, Staphylococcus aureus, that hit her at the same time as the virus, the Associated Press reported, quoting Rhode Island officials. They called it “a very rare combination,” and stressed that most people infected with Enterovirus D68 typically suffer little more than a runny nose and a low-grade fever.

“We’re saying we’re sure that the child died of staph aureus sepsis, which is an overwhelming bacterial infection. We’re sure of that,” state Health Director Michael Fine, MD, said Wednesday, the Providence Journal reported. “The virus was present in the child’s body. We’re not sure how much the presence of the virus contributed — or didn’t contribute — to the child’s death,” he added.