The state confirmed Tuesday that there have been two other deaths from the virus.
The Cook County health department is warning residents to take extra precautions as the virus continues to spread.
On Tuesday, the Illinois Department of Public Health was expediting a test to confirm a suspected fatal case of H1N1. The state won't release details but a south suburban family told ABC7 they were informed the boy likely had the virus.
On Tuesday, Matt Dampier was struggling with the sudden loss of his nephew.
"It just happened overnight. We didn't see it coming," said Matt Dampier, uncle of boy.
Dampier said his eight-year-old nephew Mark wasn't feeling well Thursday, went to a south suburban hospital Friday and was diagnosed with pneumonia, then transported to Christ Hospital where the boy died Saturday morning.
"No sooner I could get up in the morning to call to check on him, to see how he was doing...It happened too quickly," said Dampier.
Dampier said the family was told Mark likely had H1N1.
As Cook County Health officials await confirmation of the fatal case, they are seeing higher than normal emergency room visits for the flu due to H1N1.
"This is the right time to change behavior in terms of increased focus on the benefits of good hygiene as a means of preventing infection," said Dr. Michael Vernon, Cook County director of Communicable Disease Control.
As health officials urge continued attention to prevention, the Dampiers also warn parents to be alert to your child's health.
"Don't let a small fever or cold pass you by thinking its nothing because it can really turn into something like this. We never seen this coming. He was real healthy and real active and we're really going to miss him," said Dampier.
There are 600 confirmed cases of H1N1 in Cook County. Seventy percent of those cases are in patients under 20 years old.
In the meantime, school officials are monitoring federal recommendations and the production of the flu vaccine for what they may need to do in the fall.