The Centers for Disease Control has determined that the 4-year-old New Jersey boy who died at home last week had enterovirus.
It's still not clear if the respiratory illness played a direct role or was a contributing factor in his death, however, state health officials say.
The child attended Yardville Elementary School in Hamilton Township and died at home last Thursday. He's the first child to die in New Jersey of enterovirus, according to the CDC.
The boy's name has not been released.
The state health department had ruled out influenza as a cause of death after completing a series of tests over the weekend. The CDC is the only agency that can test for enterovirus, which has sickened at least 500 people in 42 states and Washington, D.C. -- almost all of them children.
New Jersey currently has nine confirmed cases of enterovirus in Morris, Essex, Passaic, Sussex, Mercer, Middlesex, Camden and Burlington counties.
Health officials say that now that the virus is confirmed in the state, the department won't test every suspected enterovirus case because a diagnosis in patients won't change clinical management or public health actions.
Enteroviruses, which usually cause mild cold-like symptoms that last about a week, are common, afflicting up to 15 million people in the U.S. each year, but the CDC says this particular strain of the virus is unusually severe.
Infants and children are at particular risk, and though most affected people recover on their own and have no future problems, those with weakened immune systems or underlying medical conditions such as asthma may need to be hospitalized. No fatalities have been reported in the tri-state area.
There is no vaccination. Prevention involves hand-washing, disinfecting surfaces and any usual steps to prevent the spread of flu.
There are more than 100 types of enteroviruses. EV-D68 was first identified in California in 1962.
Health officials urge anyone who has trouble breathing, or notices a child does, to call a doctor immediately.