HAMILTON - The U.S. Centers for Disease Control and Prevention confirmed that the Hamilton preschooler who died last week tested positive for the respiratory illness Enterovirus D-68, the N.J. Department of Health announced late Friday.

“Our thoughts remain with the family at this very difficult time,” said N.J. Health Commissioner Mary E. O’Dowd. “While the child has tested positive for EV-D68, the cause of death has not yet been determined and it is unclear if EV-D68 played a direct role or was a contributing factor in his death.”

The 4-year-old's death is the first in New Jersey involving the virus. Enterovirus D-68 has been found in at least four other people who have died in the United States, according to a report on CNN.

At a meeting Monday at Yardville Elementary School, where the 4-year-old attended the afternoon preschool session, Hamilton Health Officer Jeff Plunkett and Superintendent James Parla emphasized that the school was safe to attend.

The CDC confirmed an additional case of Enterovirus D-68 in a Middlesex County child, bringing the number of confirmed cases in New Jersey to nine. Those cases are spread across the state in Camden, Burlington, Mercer, Middlesex, Morris, Essex, Passaic and Sussex counties.

Enterovirus D-68 causes upper respiratory symptoms such as cough runny nose, sneezing and body and muscle aches and possibly a low-grade fever, according to the state Department of Health. The department warns that if a child becomes ill, parents should consult with their health care provider.

New Jersey, like the rest of the U.S., is in the middle of the respiratory virus season. Many different viruses are common this time of year, including influenza, rhinovirus and more than 100 other types of enteroviruses, according to the department.

"Enterovirus D-68 is treated the same as other respiratory illnesses that are seen in children this time of year," O'Dowd said.

There is no vaccine or specific antiviral medication for enterovirus infections.

Now that the virus is present in New Jersey, the department will not test every suspected case of Enterovirus D-68 because that will not change the clinical management or public health action, the department said in a press release.

Enteroviruses are transmitted through close contact with an infected person, or by touching objects or surfaces that are contaminated with the virus and then touching the mouth, nose, or eyes.

"Parents and caregivers should be aware that children with weakened immune systems or underlying medical conditions, such as asthma, may experience severe complications and require hospitalization with supportive therapy," O'Dowd said.

The preventive steps people can take to avoid becoming ill and the treatment are similar to those of most respiratory illnesses like the flu.

CDC has tested a high volume of specimens nationwide, and of the specimens tested by the CDC laboratory to date, only about half have tested positive for Enterovirus D-68, according to the state health department. The Department has received several tests back from the CDC that were negative for EV-D68 and we have additional test results pending. New Jersey labs cannot test specifically for EV-D68.

The CDC is also investigating whether the virus, which has been found in 514 people throughout the U.S., is connected to cases of polio-paralysis that have arisen in Colorado and California.

The Children's Hospital of Philadelphia reported Friday that it is testing for the virus in three patients with acute muscle weakness in one or more limbs, in response to the CDC's request for increased surveillance. None of these cases has been confirmed so far.

O'Dowd recommends good hand hygiene as the best defense against getting infected with enterovirus:

• Washing hands with soap and water for 20 seconds, especially after changing diapers. Hand sanitizers are not effective against entroviruses.

• Avoiding touching eyes, nose and mouth with unwashed hands

• Avoiding kissing, hugging, and sharing cup or eating utensils with people who are sick

• Disinfecting frequently touched surfaces, such as toys and doorknobs, especially if someone is sick

Jenna Pizzi may be reached at jpizzi@njtimes.com. Follow her on Twitter @JennaPizzi. Find The Times of Trenton on Facebook.