How does flu kill healthy people?

Flu vaccine effectiveness typically ranges from 40 to 60 percent in a good year. It’s unclear just how effective this year’s vaccine is. (Photo: Justin Sullivan/Getty Images)

15-year-old student at student at Newnan High School is the first pediatric flu death in Georgia, according to the Coweta County coroner.

» RELATED: Do you have the flu? 17 things to know about flu symptoms, flu shot side effects and more

The girl, Kira Molina, had liver failure, which led to her death, according to Coweta County Coroner Richard Hawk. Molina died Tuesday morning at an Atlanta hospital.

She was the latest victim in a flu season that has caused at least 25 deaths in Georgia, and has crowded Grady Hospital’s emergency room.

Certified pharmacy technician Peggy Gillespie fills a syringe with antibiotics for use as an I.V. push at ProMedica Toledo Hospital in Toledo, Ohio. (AP Photo/Tony Dejak)

Credit: Tony Dejak

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Credit: Tony Dejak

How does the disease cause death?

According to Scientific American the way the flu kills its victims can be summed up simply: "The short and morbid answer is that in most cases the body kills itself by trying to heal itself."

» RELATED: Flu season to be worst in a decade: Death toll rises to 37 children

As the virus spreads in the lungs and respiratory system, the body unleashes a counterattack, in which T-cells destroy the tissues that harbor the invading virus.

“In most healthy adults this process works, and they recover within days or weeks,” the magazine reports. “But sometimes the immune system’s reaction is too strong, destroying so much tissue in the lungs that they can no longer deliver enough oxygen to the blood, resulting in hypoxia and death.”

» RELATED: Flu season to be worst in a decade: Death toll rises to 37 children

Sometimes the lungs, weakened by the flu, become prey to another infection, often streptococcus, and the body is felled by bacterial overload, as happened to a New Hampshire mother of four earlier this month.

Worldwide, the flu causes up to 640,000 deaths annually.

» RELATED: Flu season to be worst in a decade: Death toll rises to 37 children

Doctors have long known that contracting influenza can be dangerous for the elderly, for infants and for those already in a weakened state. Almost all the victims in Georgia were over age 50. But flu can kill others as well, depending on the virulence of the particular strain that spreads during flu season.

This year's strain is the most severe in a decade.

A chart from Children's Healthcare of Atlanta can help parents determine when to seek help.