Superintendent of Schools Dr. Christopher Manno sent out a note to parents on Sunday alerting them of the death.
Friends of the family say the parents of the girl are going through an 'absolutely horrific' time right now. The girl received a flu shot on September 22nd and was described as a perfectly healthy, happy child.
Authorities say the 5-year-old kindergartener became ill at the B. Bernice Young School on Thursday afternoon during an after-school program. She was picked up by her parents and taken home.
Her condition worsened overnight, and at 8:00 a.m. on Friday an ambulance was called. She was rushed to Children's Hospital of Philadelphia where she died from complications of the Influenza B virus.
"The loss of a child is the most traumatic, deeply wounding event that I think any one of us can possibly experience," said Dr. Manno in a news conference on Monday morning.
Symptoms can include nausea, fever, aches, vomiting, chills, headache and fatigue. The school district says 14 students went home last week with flu symptoms.
"I'm telling parents to keep their children home if they're sick. If they're ill, call their doctor. Make sure that they practice good personal hygiene. Also isolate a child or an adult member of the household if they have the flu," said Burlington County Health Director Bob Gogats.
The entire school has been sanitized twice since the girl got sick, officials said.
Counselors will be available to members of the school community to help cope with the loss. Parents picking up their own children on Monday couldn't believe the news.
"It's horrible. I can't even imagine what that must feel like for that family," said Cindy O'Neil.
Flu activity in New Jersey is considered "regional," the second highest level.
Meanwhile, federal flu-watchers last week said Pennsylvania now has "widespread" flu activity, the highest level. There have been 11 confirmed flu-related deaths, according to figures for the weekend ending January 12. Lehigh, Northampton, and Lancaster counties had the biggest number of cases in the eastern portion of the state, however, numbers in Bucks and Montgomery counties are rising.
Montgomery County alone has recorded 4 flu deaths. One was child, but the others were young to middle-aged people, and most has underlying health conditions.
The state of Delaware hasn't recorded any flu deaths, and the CDC says flu activity is "sporadic," a lesser level. However, cases there are rising in recent weeks. New Castle County has the highest number, with children, and those from 5 to 24 years of age having the biggest share.