When the parents of 4-year-old Eli Waller put their son to bed last month they had no idea that the New Jersey preschooler would never have the chance to give them a good morning kiss ever again.

On Sept. 24 little Eli stayed home from school after he came down with pink eye. Although he was feeling fine by the time he went to bed, he died in his sleep from a mysterious virus known as enterovirus D68, which has put other parents in Hamilton Township, New Jersey on high alert.

While enterovirus is very common, Medical experts warn that the D68 strain of the virus is very dangerous and can cause respiratory illness.

According to Jeff Plunkett, the health officer in Eli's hometown, the boy "had no other existing condition" and his parents had no reason to believe he was ill, reports CNN.

"He was asymptomatic and fine, and the next morning he had passed," said Plunkett. "So the onset was very rapid, very sudden. And that's clearly the big difference (between enterovirus D68 and other enterovirus strains)."

One other child at Eli's school Yardville Elementary is also being tested for enterovirus D68. He was treated at Robert Wood Johnson University Hospital and is now recovering at home, according to Plunkett. Other than that, no one else is suspected to have the virus in the town of 90,000 residents. Still, parents in New Jersey have showed concerned about the spread of the virus.

"It's so scary, and I don't know anything about it," Deborah Sanchez told WABC-TV.

"They're not saying this is over with. And I guess that's what I need to hear, that it was an isolated case. It's not," said Linda Bonfonti, a grandmother of a child in the school district, reports MyFoxPhilly.com.

School officials also announced that the school is undergoing a complete scrub-down.

However, because D68 is random and pervasive, Hamilton Township Mayor Kelly Yaede stated that it is almost impossible "to determine where Eli may have contracted this virus."

"The virus is out in the community, there is nothing we can do about that," added Plunkett. "The way to prevent it is from your own personal hygiene and be vigilant with your own children and yourself."