Just 82 children have confirmed cases of enterovirus-D68, according to the CDC, but hospitals around the country say they are treating hundreds more children who have been sickened by the rare virus.

“We have some of these cases now in our ICU,” says Dr Giovanni Piedemonte, a pediatric pulmonologist and chairman of Cleveland Clinic’s pediatric institute. Children with the virus can have serious trouble breathing, he says, enough so that they have to be put on a ventilator or lung bypass machine.

But Ohio isn’t on the CDC’s list of six states with confirmed cases of enterovirus-D-68 – they are Colorado, Illinois, Iowa, Kansas, Kentucky and Missouri. Official numbers always lag in a fast-moving outbreak, but the gap appears to be particularly big with enterovirus-D68. That may be because it appears to spread easily, because milder cases often look like a cold, and because there’s no swift test to identify it.