By Mandy Oaklander
September 8, 2014

Updated Monday, Oct. 6

A 4-year-old boy in New Jersey has died from Enterovirus D68 (EV-D68), a respiratory virus that’s dominated flu season this year, Reuters reports. The virus was noted as the cause of death in the young boy, who died in his sleep without displaying any symptoms of the virus. Four people who have died so far had EV-D68, though the role of the virus in their deaths is unclear, the CDC says.

The CDC and state health officials have confirmed EV-D68 as the cause of respiratory illness in 538 people—almost all of them children—across 43 states. EV-D68 seems to be the predominant type of enterovirus this year, the CDC says on their website, and it’s most common in children affected with asthma or wheezing.

Last month, the CDC said that hundreds of children in Missouri had been hospitalized for respiratory illness, the virus being one of the causes, the organization said Sept. 8 in a press conference.

EV-D68 presents like the common cold at first, but it can cause rash, neurologic illness, and—most commonly—mild or severe respiratory illness. Serious symptoms include wheezing and difficulty breathing.

“The unusual increases in Kansas City and Chicago may be occurring elsewhere in the weeks ahead, so we want people to be on the lookout,” said Dr. Anne Schuchat, director of CDC’s National Center for Immunization and Respiratory Diseases. The Missouri Department of Health and Senior Services issued a recent health alert that a pediatric hospital in Kansas City saw more than 300 recent cases of respiratory illness, 15% of which required intensive care. Of the 22 specimens the CDC tested from that hospital, 19 were positive for EV-D68.

Another children’s hospital in Chicago reported similar increases, and of the 14 specimens collected there, 11 tested positive. Children with asthma seem to be especially at risk: Half of those cases occurred in children with a previous history of asthma or wheezing, Schuchat said.

Many children affected by the virus will recover just by treating symptoms, Schuchat said, but the CDC urges parents to seek medical care if their child has difficulty breathing.

Though it’s rarely reported in the United States, this virus isn’t new, and the first known case was identified in 1962 in California. Not a lot is known about it, but it does seem similar to other enteroviruses in several ways: it largely affects children and spreads through saliva and mucus (so: coughing, sneezing, and touching infected surfaces).

No vaccine exists for EV-D68, though Schuchat urges the influenza vaccine to protect against other viruses.

“We’re in a stage where it’s difficult to say just how big this is, how long it will go on for, and how widespread it will be,” she said.

Write to Mandy Oaklander at mandy.oaklander@time.com.

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