Since the middle of August, 594 people in the U.S. have contracted Enterovirus D68, a new strain of a common virus that has been sweeping through the country, affecting mostly children. There are more than 100 enteroviruses that usually affect children during the summer months, but this particular one can cause very severe respiratory symptoms and has sent children to the hospital with breathing problems. Last week the virus killed a 4-year-old in New Jersey who had appeared healthy.

Experts say parents can protect their children from the virus the same way they would from a common cold, but should be especially vigilant about respiratory symptoms.

“It really hit Missouri right at the beginning of the school year, which isn’t surprising,” Dr. Gail Shust, assistant professor of pediatrics and infectious diseases at the Icahn School of Medicine at Mount Sinai in New York City, told CBS News. “Kids are great at spreading germs and also parents are reluctant to keep kids home at the start of the school year.”

Enterovirus D68, also known as EV-D68, spreads the same way as the common cold: An infected person coughs, sneezes or touches a surface, which is then touched by others. Children are more likely to contract it because they haven’t yet developed immunity.

“In general, a mix of enteroviruses circulates every year, and different types of enteroviruses can be common in different years,” according to the Centers for Disease Control and Prevention. “However, this year the number of people reported with confirmed EV-D68 infection is much greater than that reported in previous years.”

For most patients, the virus presents with symptoms such as fever, runny nose, sneezing, cough and muscle aches. Some patients experience severe respiratory problems such as difficulty breathing and wheezing -- especially if they also suffer from asthma.  

“The most important thing to pick up on is any difficulty breathing,” Shust told CBS. If the child is wheezing or has a cough that won’t go away, “parents should have a low threshold for heading to the hospital with that.

Frighteningly, 4-year-old Eli Waller, the New Jersey boy, seemed in good health apart from a case of pinkeye the night before he died on Sept. 24, according to local reports. “He was asymptomatic and fine, and the next morning he had passed,” Jeffrey Plunkett, the township’s health officer, told the New York Times. “The onset was very rapid and very sudden.”

While there aren’t any specific medications for the enterovirus, the CDC recommends parents give children over-the-counter medicines to help with the pain and fever, with the caution aspirin should not be used. However, anyone with a respiratory illness should contact a doctor if symptoms worsen.

To protect against infection, the CDC recommends children wash their hands often -- with hot water and soap -- for at least 20 seconds. They should also avoid close contact with others and keep away from anyone who seems sick. Parents should clean and disinfect frequently touched surfaces like toys or doorknobs, and keep children who feel sick home from school.