It doesn't matter if you are young, healthy or even run marathons – when it comes to flu, no one is completely immune.
That's the warning families of flu victims and health officials are hoping to spread as this year's flu season takes more and more lives across the U.S.
The predominant virus this season, Influenza A (H3N2), primarily affects the elderly and the very young, but epidemiologist Lynnette Brammer, who leads the CDC's Domestic Influenza Surveillance Team, told Fox News the flu can hit anyone.
"Sadly, we hear every year of people that were previously healthy and active and they get influenza and die and for reasons we don’t understand," Brammer said. "[But] if you get sick and you're not getting better...call your doctor."
Here are some of the stories of people tragically lost to the flu this season.
Emma Splan, 6
A Connecticut school is urging students to get vaccinated after the death of "one of its own," 6-year-old Emma Splan, due to flu complications.
The Elizabeth Public School District confirmed Splan, a student at Columbus Magnet School in Norwalk, Conn., had been diagnosed with Influenza prior to her death.
"I offer our thoughts, condolences, and prayers to the family at this heart-wrenching time," superintendent Olga Hugelmeyer wrote in a letter to parents on Feb. 18.
Sarah Lutkus, a family friend, told WNBC Splan's parents "did it the right way."
"They got her a flu shot. They got her to a doctor," Lutkus told WNBC. "They’re the best parents a child could have. They didn’t wait. They didn’t linger. And apparently we all know this flu season is crazy."
The young girl was taken to the doctor at the first sign of the flu. Doctors confirmed she had Influenza on Feb. 15.
Three days later, her parents took her back to the doctor. She was later transferred to a nearby hospital, where she died on Feb. 18.
State health officials have not officially determined the cause of Splan's death, but Norwalk Mayor Harry Rilling told WNBC it's being investigated as flu-related.
Nevaeh Hernandez, 6
The flu has claimed the life of a young New Jersey girl.
Nevaeh Hernandez, 6, died of the flu, health department officials confirmed on Feb. 13.
After the young girl contracted the flu, her health faded fast. This led her father, who is stationed with the military in Germany, to fly home, according to CBS New York.
Hernandez later passed away at a local New Jersey hospital, the New York Post reported.
"Nevaeh was a beautiful 6 year old full of life who brought happiness to all who surrounded her," reads the GoFundMe page that was created to help the family offset funeral and medical costs. "A child’s death is beyond devastating in which no parent should ever have to endure. The grief seems to be endless."
Before her death, Hernandez was a kindergarten student at Lincoln Elementary School North Bergen. A family friend told CBS New York that the young girl's favorite color was pink.
Alivia Viellieux, 3
Aabriey Viellieux rushed her 3-year-old daughter, Alivia, to the emergency room after the little girl tested positive for Influenza A.
The toddler's symptoms appeared to be getting worse. But Viellieux says her daughter was released from Ball Memorial Hospital in Muncie, Indiana, nearly 48 hours later.
"I asked them over and over if there was anything I needed to be worried about and they said 'No, she should be better by the weekend,'" Viellieux told Fox59.
Over the weekend, Alivia's condition seemed to improve. But on Sunday, Feb. 11, she started to feel sick again.
The next morning, Viellieux's daughter was dead. Her flu had apparently developed into pneumonia, a complication Viellieux was unaware her daughter had.
"It happened in just a day, because she was literally... I thought she was getting better," Viellieux told the news station.
The girl's sudden death came as a shock to the family, who thought she was recovering. Viellieux said she never would have brought her daughter home if she knew she was still sick.
"I'm sure every one has seen the reports and media that my grandbaby passed away this am from the flu," Alivia's grandmother, Tameka Stettler, posted on Facebook on Feb. 12. "I can't stress to anyone [enough] to be safe."
Friends set up a GoFundMe page to help pay for the little girl's funeral.
Angie Barwise, 58
When Angie Barwise found out she had the flu for the second time this year, she didn't hesitate to seek treatment.
The 58-year-old wife and mother was diagnosed with Type A Influenza a few days after Christmas and was told she also had strep and bronchitis. A month and a half later, she found out she had been hit with Type B Influenza.
She went to the doctor and received Tamiflu and antibiotics, but her symptoms seemed to just get worse.
"The fever just continued,” Barwise's husband, Greg, told Fox 4. “Every four and a half hours, we'd have to give her medicine to get the fever down."
Greg took her back to the hospital on Jan. 31 and doctors said she developed pneumonia and sepsis, complications from the flu.
Days later, on Feb. 3, Barwise died. Now Greg is sharing his wife's story to warn others to watch out for secondary infections.
"I want people to know to take this serious,” he said. “She's the love of my life. She's everything in the world to me."
Jenna Libidinsky, 24
Jenna Libidinsky started feeling sick around Jan. 25.
Family members said the 24-year-old from Las Vegas, Nevada, went to the doctor five times over the course of eight days.
She was diagnosed with the flu, handed cough syrup, antibiotics, an inhaler and sent home to rest.
“What do all doctors tell us when you have a bad chest cold? A cough is going to be around for a couple of weeks. OK, so, that’s what we’re thinking,” her father, Neil, told the Las Vegas Review-Journal.
But Libidinsky didn't just have a cold.
In the middle of the night, Neil awoke to the sound of his daughter's scream. She had collapsed.
He called 911. Paramedics performed CPR on the young woman for about two hours, but it was too late. Her lungs had failed.
On Feb. 7, Libidinsky died. Her family was devastated.
“Go hug your children,” her mother, Marla, told the Vegas newspaper.
“The pain of losing her is worth knowing her for 24 years," Neil added.
Heather Holland, 38
Second-grade teacher Heather Holland started feeling sick on Jan. 29, but she went to school anyway.
When the 38-year-old's symptoms got worse, she visited a local clinic, where she was diagnosed with Influenza B.
Two days later, as her health continued to decline, she went to Harris Methodist in Fort Worth, Texas. Doctors said she was suffering from pneumonia, which she developed from the flu, according to Fox 4 News.
They placed her on dialysis, but her condition didn't improve. The wife and mother of two died on Feb. 4.
"She wouldn't go get medicine because she's a mama. Mama's are tough. She just kept going. She had a job; she had kids," Holland's pastor, Clark Bosher, told Fox 4. "I think any mom does that. I don't think she is being irresponsible. I don't think she thought she was that sick. It happened so quick."
Weatherford school district confirmed the teacher's death and said Ikard Elementary School, where she worked, has since received a deep cleaning.
“As you might expect, today is a difficult day at that campus and we are working our processes to care for students, parents, and staff,” Weatherford ISD said in a statement.
Aaron Masterson, 12
Aaron Masterson died at Huntsville Hospital in Georgia on Feb. 4 due to complications from Influenza B.
The 12-year-old had cystic fibrosis, a "genetic disease that causes persistent lung infections and limits the ability to breathe," according to the Cystic Fibrosis Foundation. The diease worsened his flu symptoms, WHNT reported.
"We constantly are already going back and forth of between tears. Tears of sadness, then tears of joy," family friend, Brandy Worthy, told WHNT. "Sharing videos about him and laughter."
Masterson's pastor, John Mullaney, said the family plans on donating his organs.
"He's a hero. I mean he was just not somebody who complained. He impacted so many people, just in the way that he lived his life and who he was," Mullaney said.
Huntsville Junior High School confirmed Masterson's death in a letter sent home to parents.
"As a school community, we send our condolences to his family and friends," principal Stephanie Wiseman wrote. "We will support the Masterson family and our students as we navigate the process of loss with counselors and lots of love."
Savanna Jessie, 7
A community is mourning the death of 7-year-old Savanna Jessie, who tested positive for influenza B, strep throat and scarlet fever.
The first-grader, who lived with her father in Columbus, Indiana, died "suddenly" at Columbus Regional Hospital on Feb. 1, according to a YouCaring post on a page created to help cover funeral expenses.
"We got news Friday that she had been sick and that [her father] had taken her to the hospital Thursday evening," Savanna's aunt, Courtney Hargett, said in a WBRC report. "And that after they left the hospital, he took her home, put her in bed, and then found her Friday morning.”
An autopsy confirmed Jessie had the flu, strep throat and scarlet fever -- a bacterial infection caused by strep, but an official cause of death has not yet been released, pending further tests, reported Fox 59.
"There is no vaccine to prevent scarlet fever," according to the CDC.
Bartholomew Consolidated School Corporation (BCSC) confirmed the girl's death in an online statement released on Feb. 2.
"We recognize the concerns of our families regarding the flu," BCSC Superintendent Jim Roberts said. "BCSC makes up one part of the community’s responsibility to keep our children healthy throughout the year. It is important to note that the precautions taken at school should continue in other environments in our community."
Roberts encouraged students and staff to get a flu shot.
"It is not too late to receive a vaccination for this year’s flu season," he added.
Kira Molina, 15
When Kira Molina started showing symptoms of the flu, her parents immediately drove her to a nearby clinic in Newnan, Georgia
Doctors said Molina's flu tests came back negative.
Her parents were stumped. They took her home and hoped whatever "bug" she had would eventually pass on its own.
Days later, they found her unresponsive and drove her to a local hospital. She was eventually transferred to Children's Healthcare of Atlanta, where her health continued to decline.
Two days later, on Jan. 30, Molina died of of Influenza A.
According to WSB-TV, the Coweta County coroner, Richard Hawk, confirmed the girl's death during a press conference the next day. Hawk said Molina had the flu and had liver failure, which led to her death.
When asked about Molina’s initial false flu test, the coroner said most tests are done quickly, and Molina likely took a rapid flu test which is about 63% accurate.
“That means about one in three tests is going to have a false positive,” Hawk said.
Molina was the first pediatric death in the state.
Eli Snook, 5
Eli Snook's parents didn't want to take any risks when their 5-year-old son spiked a high fever and showed other signs of the flu.
They took him to an urgent care center in Marietta, Georgia, where a doctor gave him antibiotics and prescribed him Tamiflu, his parents told WSB-TV.
After spending about a week resting and taking his medication, Snook appeared to be better and his parents took him back to day care. Three days later, on Jan. 27, they were asked to pick him up early because he had a temperature of 101 degrees.
They brought him back to the walk-in clinic. Doctors ran some more tests and confirmed he tested negative for the flu. They told his parents they were concerned about a rash they noticed across his body, CBS News reports.
Due to the combination of a fever and rash, doctors transferred Snook to Children's Healthcare of Atlanta, where he later died from a brain infection that developed while he had the flu.
Doctors told Snook's parents the flu weakened his immune system and a virus "quickly attacked" his brain.
"We prayed for a miracle," Snook's father, Aaron, told WSB-TV. "He got an infection in the brain. His brain swelled past the point of no return, and he went brain dead."
"It was a shock to me. It was shock," Snook's mother, Leota, added.
Snook's mom hopes her son's story will show parents that it's not just the flu that's killing children this season.
"It's the after-effects of the flu that's killing these babies," Leota said.
Kevin Baynes Jr., 7
When Kevin Baynes Jr., 7, was sent home from school on Friday because he wasn't feeling well, his family never expected to lose him just two days later.
On Saturday, after Baynes' flu-like symptoms persisted, his parents took him to the emergency room. Doctors later diagnosed him with both strep throat and the flu, and sent him home, WTVR reported.
But early the next day, Baynes’ older sister found the Virginia boy unresponsive when she went to check on him.
The medical examiner in Virginia is investigating Baynes’ death but if confirmed to be flu-related, he will be the first child to die of the illness in the state this year, WTVR reported.
"Watch your children closely," Baynes' mother, Samantha Baynes, said. "Don't hesitate to go to the emergency room. No matter what time it is day or night, just take them."
Additionally, Baynes’ cousin set up a GoFundMe to help the family with funeral expenses. “His parents are devastated and shocked,” the relative wrote.
Dulce Estrella, unborn
The flu has taken the life of at least one unborn child this year.
Maria Paniagua of San Jose, Calif., who was seven months pregnant with her fifth child when she caught the flu, lost her unborn baby earlier this month due to the illness.
After Paniagua caught the flu, doctors were forced to make a tough choice: Save Paniagua or save her unborn child, Dulce Estrella. They chose to save Paniagua.
“It was so, so severe that they couldn’t do a cesarean when the baby’s heartbeat was not viable," Diana Barron Gonzalez, Paniagua's best friend, said. “If they would have operated on her with the cesarean, they would have lost her, or the child or both,” she added.
Paniagua also caught pneumonia -- leading doctors to put the young mother into a medically induced coma to help her breathe. Dulce Estrella was stillborn a day later.
“Be careful with the flu, with influenza. So be very careful with that if you’re pregnant. You go into the hospital and either you or your baby can survive, but maybe not either one survive. Both can die," Jocabeth Barraza Hernandez, Paniagua's mother, said.
Paniagua is alive and recovering. A GoFundMe has been set up to help Paniagua, a single mother, with expenses.
Katherine Acton, 47
Friends and family members of Katherine Acton were shocked by the flu-related death of the Alabama mother of two. After all, she was "one of the healthiest people" they knew.
Acton had a trainer, followed a strict diet and was getting ready for a fall wedding with her fiancé, Chuck Benzil.
"She would train with me two to three times a week, and she would work out on her own two to three times a week," Brii Walker, Acton's personal trainer, told Fox 6.
Acton died just one week after she was diagnosed with the flu.
Her death is a frightening reminder that healthy people can succumb to the sickness, too, her friend, Donna Mann, told the news station. Now, she's sharing the 47-year-old's story to warn others.
"The loss of her might save someone else, from her sharing what she was going through and what she was feeling," Mann said.
Jenny Ching, 51
Jenny Ching, a wife and mother of two, was admitted to the hospital in early January for what was maybe just a bad cold.
But two days later, the 51-year-old died.
After she was admitted to the hospital, the Needham, Massachussets, resident was diagnosed with the flu which quickly turned into other illnesses.
"She had the flu and she also developed a bacterial infection. It was really severe and caused severe pneumonia," her husband, Matt Ching, told WCVB. He said that he wasn't sure if his wife got the flu shot this year or not.
Ching died on the morning of Jan. 5.
"I can't believe it because she was so healthy," Raymond So, the owner of the Chinese restaurant where Jenny worked, told WCVB. "She was so happy and driven."
Ching is survived by her husband, two sons, ages 9 and 7, and many other family members. A GoFundMe has been set up to help the family with expenses.
Dylan Winnik, 12
When Dylan Winnik told his parents he felt sick, they thought he had a cold.
They had no idea how serious the 12-year-old Florida boy's illness was until it was too late.
By the time deputies with the Palm Beach County Sheriff’s Department arrived at the home of the seventh-grader's father on Jan. 23, Winnik was dead, the Palm Beach Post reported.
Now Winnik's family is sharing their story about the boy, who they say did not receive a flu shot this year, to encourage others to take the illness seriously this season.
“Please implore other parents to not take the flu lightly whatsoever,” Mike Medwin, the boy’s mother’s partner, told the Post.
Lily Kershaw, 5
Lily Kershaw, 5, died of flu-related complications on Jan. 21. She's the first child to die from the flu in Nebraska this year, according to health officials.
“We started seeing increased flu activity earlier than usual this year and flu continues to circulate at very high levels,” Dr. Tom Safranek, state epidemiologist for the Nebraska Department of Health and Human Services (DHHS) said in a statement following the girl's death. “During a severe flu season, we see more illness, hospitalizations and sadly more deaths.”
Kershaw's school, Twin River Kindergarten in Silver Creek, Nebraska, confirmed the girl's death in a Facebook post.
"Heaven gained a beautiful angel this morning," the Facebook post read. "Lily was a smart, kind, and loving little girl. She had a passion for learning and always shared her big smile or a hug with anyone in need of one."
While the nation is facing an unusually severe flu season, health officials say flu-related deaths in the state are rare.
"So far, there have been a total of 22 flu-related deaths statewide - 21 adults and one child," DHHS says.
Karlie Illg Slaven, 37
Karlie Illg Slaven was constantly on the move as she cared for her two kids and husband, who were all home sick with the flu.
By the end of the week, the 37-year-old mom also started to feel ill.
“Karli had to take care of all of them and she got kind of run down and tired,” Slaven's father, Karl Illg, told Fox 59.
Slaven went to a walk-in clinic for an exam. She was told she had the flu and was sent home to rest.
The next day, Slaven had some trouble breathing. So she went to a hospital in Hendricks County, Indiana, to take some tests.
“They took x-rays and her lungs were clear. But, she did have the flu and was still struggling to take deep breaths,” Illg said.
Again, Slaven headed home.
But her breathing only continued to get worse and she was rushed to the emergency room, where she died 24 hours later, on Jan. 21. Doctors said her death was a result of pneumonia, a complication from the flu.
“I never even got a chance to talk to her again,” Illg said.
Unlike her kids and husband, Slaven didn't get the flu shot this year, Illg said.
“Even if it only gives you a 10 to 20 percent edge to fight off the flu, that 10 to 20 percent might have saved Karlie’s life," Illg said. "It is one of those things that we are all going to have to wonder about. What if."
Emily Muth, 6
When Emily Muth started feeling sick, her parents took her to an urgent care location, where she tested positive for the flu.
The doctor handed the 6-year-old's mother, Rhonda, a prescription for Tamiflu, an anti-viral medication, and told the little girl to get lots of rest and drink plenty of fluids.
Three days after her flu diagnosis, Muth started to have difficulty breathing. Her mom called an ambulance.
A paramedic who arrived at the house told Rhonda labored breathing was a side effect of the flu. It wasn't cause for concern.
"He asked us you know, 'We can take her.' And, you know, they're the medical personnel," Rhonda told WTVD. "I trust what they know. And they said she was fine."
But she wasn't.
Hours later, Muth's breathing got worse.
"She was breathing a little bit heavier. And all of sudden she just raised up and went back down," Rhonda described. "I went, 'Emily, Emily.' And I noticed she wasn't breathing."
Again, Rhonda called 911. But it was too late.
By the time the ambulance reached WakeMed Hospital in Raleigh, North Carolina, Muth was gone. The 6-year-old died on Jan. 19.
"This flu is no joke and didn't have to happen," Rhonda wrote on a GoFundMe page to raise money for her daughter's funeral. "Please, all of you who have children, please hold them tight and [at the] first sign of flu get them to the ER."
Tandy Harmon, 36
Tandy Harmon skipped a shopping trip with her friend because she was starting to feel under the weather.
The 36-year-old single mother of two assumed she had a simple case of the flu. Harmon planned to sleep it off, but she went to the hospital to get herself checked out as a precaution.
Doctors confirmed the mom from Gresham, Oregon, had the flu and sent her home to rest and hydrate.
Two hours later, Harmon's boyfriend, Brad Fauts, drove her back to the hospital. Her symptoms were getting more severe.
“[They] immediately put her on a ventilator and from there she just went downhill,” Fauts told Fox 12. “By that evening, she was on life support.”
Within two days, Harmon was dead.
Doctors told Fauts her organs shut down as a result of pneumonia and Methicillin-resistant Staphylococcus aureus (MRSA) – an infection caused by staph bacteria that's resistant to several antibiotics – which she developed while her body was vulnerable from the flu.
Now Fauts is sharing Harmon's story to warn even the healthiest people to be vigilant this flu season.
“Don’t mess around with this flu,” warned Fauts. “If you feel something wrong in your body, go to the doctor and insist that they see you.”
Nico Mallozzi, 10
Nico Mallozzi started feeling sick before participating in The Cup North American Championship hockey tournament in Buffalo, New York.
The 10-year-old from New Canaan, Connecticut, reportedly left the tournament early, and was later rushed to a hospital, where he died on Jan. 13.
The fourth-grader's death was a result of “Flu type B that was complicated by pneumonia,” a medical examiner confirmed to Fox 61 two days after the boy's death.
Dr. Bryan Luizzi, superintendent of New Canaan Public Schools, sent a letter home to parents memorializing Mallozzi and urging students to get the flu vaccine recommended by the Center for Disease Control (CDC).
“Nico was a wonderful, enthusiastic, outgoing boy who was known school-wide for his high spirits, limitless energy and quick smile,” Luizzi wrote in the letter, which was posted on the school’s website Monday. “We will miss Nico terribly, and will always cherish our memories of him as a vibrant, fun-loving boy.”
Katie Denise Oxley Thomas, 40
With three kids, Katie Oxley Thomas was always running around. And on top of that, somehow the San Jose mother also squeezed in marathons and the occasional yoga session.
Her family never expected she would die from the flu.
"It was very shocking for us. We just thought she was going to leave the hospital in a couple of days and come home," Thomas' stepmother, Adrienne Oxley, told KTVU.
But on Jan. 4, just four days after she was diagnosed, Thomas died. Doctors said the flu lead to pneumonia, and Thomas' death was a result of septic shock.
"The one doctor said I've never seen anything progress like this. He said this is just incredible," Thomas' father, Walt, told the news station. "Most of us get the flu and recover from it and a handful of people every year don't. And you just don't think it's going to be your daughter. But you really want to take it serious."
Alyssa Alcaraz, 12
Four days before her death, Alyssa Alcaraz was diagnosed with the flu and sent home from a local urgent care with some nausea medicine and cough syrup.
But the 12-year-old girl's health continued to deteriorate over the next four days. She became lethargic and had trouble breathing.
Her mom, Keila Lino, took her back to urgent care, where she was told her oxygen levels were low and was transported to a nearby hospital.
Hours after arriving at the hospital, Alcaraz went into cardiac arrest and died on Dec. 17.
It wasn't until days later, that Lino learned her daughter's death was a result of septic shock from a strep infection in her blood – an infection she had no idea her daughter was suffering from.
“I know right now with the flu season clinics, hospitals, everyone is just busy and assuming that’s what everyone has,” Lino said. “But it’s more than that. In order for us to know, with simple blood work, it could have been caught. Something so simple.”
Kyler Baughman, 21
As an avid bodybuilder, a chiseled Kyler Baughman was the picture of health.
So, when the 21-year-old from Pittsburgh said he felt too sick to exercise, his family knew something was wrong.
Baughman came home early from work one night with a mild cough.
“He kinda just laid down and went about his day, and that was the day he was coughing and said his chest hurt,” his fiancée, Olivia Marcanio, told WPXI.
Nearly 48 hours later, Baughman was taken to the emergency room and airlifted to a nearby hospital, where he died of organ failure caused by septic shock from the flu, Baughman's family said.
Katharine Gallagher, 27
When Katharine Gallagher fell ill with the flu, she planned to just sleep it off.
But as time passed, the 27-year-old's symptoms only got worse.
So, she decided to go to urgent care, where she was given fluids and antibiotics. Two days later, on Dec. 5, she was dead.
"The next thing we know, we got a call from her boyfriend...saying that it was bad and the paramedics were there," Katharine's mom, Liz, told KTLA. "And so after about 10 minutes, he said to me, 'They’ve called it' — worst thing I’ve ever heard in my life."
Gallagher's sudden death was a result of severe acute bronchial pneumonia — a complication caused by the flu, her mom said.
Now Liz is warning others who catch the flu this season to seek treatment early.
"Young people just think they’re invincible, and most of them don’t want to pay what it costs now to go to doctors," she told KTLA. "Life is short...nobody ever thinks it will happen to them."
Alani Murrieta, 20
Alani Murrieta, a 20-year-old mother of two, died just one day after being diagnosed with the flu, family members told Fox 10.
The Arizona mom, who had a 2-year-old and 6-month-old, left work early after feeling sick.
“Monday she was still feeling sick, so her sister took her to urgent care, her and her kids,” Stephanie Gonzales, the woman’s aunt, told Fox 10. “They diagnosed them with the flu, sent her home with flu meds.”
The next day, Murietta took a turn for the worse. Her mom rushed her to the hospital, where she was diagnosed with pneumonia, placed on a ventilator and pronounced dead within hours on Nov. 28.
“Never in a million years would we have thought we would have lost her that day like this,” Gonzales told the news outlet.
Fox News' Madeline Farber contributed to this report.