A respiratory illness that almost exclusively infects children and for which there is no vaccine has struck Denver, Colorado, the latest in a series of infection clusters in the Midwest; one Denver hospital alone has treated more than 900 children for the illness since August 18, though no deaths have been reported. Health officials believe that the sickness is related to a rare virus called human enterovirus 68 (HEV68), the [Denver] Post says. HEV68, first seen in California in 1962, and an unwelcome but highly infrequent visitor to communities worldwide since then, is a relative of the virus linked to the common cold (human rhinoviruses, or HRV), according to the Centers for Disease Control and Prevention. ... HEV68, which almost uniquely affects children, tends to first cause cold-like symptoms, including body aches, sneezing and coughing. These mild complaints then worsen into life-threatening breathing problems that are all the more dangerous to children with asthma. Since viruses do not respond to antibiotics, hospitals have treated the illness with asthma therapies.