The recent outbreak of enterovirus D68 infections has public health officials and physicians scrambling to manage the spread and treatment of the rare but serious respiratory illness caused by the virus. Children in the Denver, Colorado, area are flocking to hospital emergency rooms with the illness.

Since August 18, Children’s Hospital Colorado has treated over 1,750 children for severe respiratory illness in its urgent-care locations throughout the Denver area as well as in its emergency room.

Over 150 children have been admitted to the hospital for follow-up care. Just in the past week, over 800 new cases have been reported. Hospital spokeswoman Elizabeth Whitehead said that the outbreak is not showing any signs of letting up. Between Tuesday morning and Wednesday afternoon, nearly 200 new cases were reported.

According to the U.S. Centers for Disease Control and Prevention, the virus has infected many children in at least 11 states. The culprit is enterovirus D68, one of many non-polio enteroviruses that causes fewer and less-frequent infections than a number of other enteroviruses. Enterovirus D68 was first discovered in California back in 1962 and has caused few outbreaks in the years since it was identified.

Enterovirus D68 causes mild to severe respiratory illness; the full spectrum of symptoms is not well characterized. Although the way in which enterovirus D68 is transmitted is not known, experts speculate that the virus likely spreads from person to person when an infected person coughs, sneezes, or contaminates surfaces.

There is no specific treatment for enterovirus D68. Severe cases require intensive supportive therapy.