The disease causes muscles to atrophy, leaving some victims paralyzed and unable to breathe on their own. Of more than 400 patients stricken since 2014, most have been children, the CDC reports. Just as frightening: Doctors don’t know what causes it — many suspect viruses like the ones that cause the common cold and other respiratory illnesses. AFM isn’t believed to be contagious, but the viruses that may lead to AFM are. Researchers don’t know why there has been an increase in reported cases starting in 2014. Nor do they know who is at higher risk for developing the condition. There is no cure and no vaccine.