A third child has died of flu-related illness in the...

A 5-year-old Brooklyn girl has become the fourth child in the city to die from the flu in the past two weeks, authorities said Sunday — as doctors urged parents to immunize their kids against the nasty outbreak.

The latest little victim, Elisa Murray, was found unresponsive in her Canarsie home Saturday night, police sources said.

The child was discovered around 9 p.m. in the bathroom by her mother, who then frantically banged on a neighbor’s door for help.

“[The mother] was crying, ‘Save my daughter!’ ‘Help me!’ She was crying for anybody to help her,” said the next-door neighbor, Nelson Martis.

Elisa “was warm, but she wasn’t moving, even though I tried to hold her nose, blow into her mouth, hearing the mother in the background, hearing the neighbors yelling and screaming,” said Martis, a schoolteacher, shaking his head as he described futilely trying to save the girl.

“She was not responsive at all. We tried to breathe into her mouth, pump the heart. … I tried to do CPR until the Fire Department came, and then they came and tried, and it all went down bad.

“She wasn’t moving at all. It seemed like it was already a done deal for her.”

The child was rushed to Brookdale Hospital, where she was pronounced dead, sources said.

Her mother told cops she had been battling a high fever, sources said. The child tested positive for the flu virus posthumously, sources said.

It was not clear if she had been diagnosed before the tragedy.

Three other city children have died of flu-related illnesses in the past two weeks, including an 8-year-old Queens girl — the first flu-related fatalities for kids in the Big Apple all season.

“The influenza season is far from over, and it is not too late to get the flu shot,’’ a city Health Department rep said Sunday. “We urge parents to protect themselves and their families by getting this potentially life-saving vaccine today.”

Multiple doctors agreed.

“Our winters have shifted, and March can be the worst month,” pediatrician Harris Burstin told The Post. “[The] flu is around until April.

“What I’m seeing is that children who have had the flu shot are less sick,” he said.

Dr. Brian Apatoff added, “Cases are still spiking now, we’re still in a very vulnerable situation. People need to continue to take precautions.

“There’s no shortage of vaccinations both at physicians’ offices and at the neighborhood pharmacies. It’s available, it’s accessible, and it’s recommended you take advantage of it, although preferably before the onset of a flu pandemic.”

Last year, six children died of the flu in the city. Typically, there are between zero and eight flu-related deaths of children in the city each year, health officials said.

Parents calling the city’s 311 hot line Sunday were told to get their kids vaccinated ASAP.

“Children between the ages of 6 months and 5 years are considered high risk and should get vaccinated as soon as possible,” a city worker told one parent.

A Manhattan social-awareness activist, Peggy Shepard, said that despite the surge in flu cases, there’s still confusion over what parents and residents should do.

“People are confused about whether to get a flu shot and whether the flu shot is effective with this strain,” Shepard said. “The city Health Department needs to be more forceful in saying what needs to be done. I thought the authorities would have done more earlier.”

Gov. Cuomo on Thursday directed the state Department of Health to green-light emergency assistance to New York’s counties, citing a whopping 35 percent increase in lab-confirmed flu cases in a single week.

That data also showed a 2 percent increase in hospitalizations, his office said.

Cuomo’s Feb. 9 directive followed a Jan. 25 executive order in which the governor declared a state of emergency and suspended a law that typically bans pharmacists from inoculating those between ages 2 to 18. Generally, that age group must see a primary-care physician.

Additional reporting by Linda Massarella, Carl Campanile and Emily Saul