By Scott Malone

BOSTON (Reuters) - A Rhode Island child hospitalized with Enterovirus D68 has died of a bacterial infection, in what state public health officials described on Wednesday as an unusual and dangerous combination.

The child, a 10-year-old girl who was not named, died last week as a result of a staphylococcus aureus sepsis alongside the respiratory virus, the Rhode Island Department of Health said in a statement, calling it a "very rare combination that can cause very severe illness in children and adults."

An outbreak of Enterovirus D68 has swept the country, with 500 confirmed cases, mostly children, in 42 states plus the District of Columbia, according to the Centers for Disease Control and Prevention.

The Rhode Island girl was the fourth person infected with EV-D68 in the United States to die this year, according to the CDC, though the agency noted that the role the infection played in their deaths was "unclear."

The girl had been hospitalized for less than 24 hours when she died, and doctors do not know how or when she acquired the bacterial infection, said Christina Batastini, a spokeswoman for the state health department.

"What we do know is that she presented with some sort of respiratory issues, difficulty breathing," Batastini said. "Her parents did all the right things, they took her to the emergency room immediately by ambulance and by the time she got to the hospital, the conditions became dire."

Staphylococcus aureus is one of the most common bacteria and can be found in hospitals and other healthcare settings. Public health experts have long been concerned about it, especially in its drug-resistant form.

Officials were careful to remind the public that very few people who contract Enterovirus D68 will develop symptoms beyond a runny nose and low fever.

"Many of us will have EV-D68. Most of us will have very mild symptoms and all but very few will recover quickly and completely," Michael Fine, director of the state Department of Health, said in a statement.

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Rhode Island officials declined to identify the hospital that had treated the girl or name the city where it was located.

EV-D68 is one of more than 100 non-polio enteroviruses, a group of viruses that are common at this time of year and cause 10 million to 15 million infections in the United States annually.

(Reporting by Scott Malone; Editing by Susan Heavey and Eric Beech)