Kyler Baughman seemed to be the face of fitness.

The aspiring personal trainer filled his Facebook page with photos of himself riding motorbikes and lifting weights. The 21-year-old once posted an image of a kettlebell with a skeleton, reading: “CrossFit, hard to kill.”

So when he came down with the flu, his mother said, he possibly assumed he simply needed rest.

“I think he thought, ‘I just got the flu; I’ll be all right,’ ” his mother, Beverly Baughman, told NBC affiliate WPXI.

But days after Christmas, Kyler Baughman was worse — coughing and running a fever, his family told the station.

They said he went to a nearby hospital, in western Pennsylvania — and, from there, was flown to UPMC Presbyterian in Pittsburgh.

Soon after, on Dec. 28, he died of “organ failure due to septic shock caused by influenza,” his mother told WPXI.

Kyler Baughman, from Latrobe, had gone home for the holidays with “a snotty nose,” his mother recalled in an interview earlier this week with WPXI.

“We saw him the 23rd for our family Christmas get-together and we noticed he wasn’t feeling well,” Beverly Baughman told the news station.

The day after Christmas, Kyler Baughman went back to work — he earned a living as a mover at a local furniture store and as an unloader at Walmart, according to his social media accounts.

But he could not make it through the day.

Olivia Marcanio, who was identified by WPXI as Baughman's fiancee, declined to comment to The Washington Post, but told the station that Kyler “just laid down and went about his day, and that was the day he was coughing and said his chest hurt. He had a mild cough.”

Now — not even two weeks after his death — his mother said: “It doesn’t seem real.”

Each year, as many as 650,000 people die from respiratory illnesses related to influenza — an increase from the previous decade, when that number was 250,000 to 500,000, according to recent data from the Centers for Disease Control and Prevention and the World Health Organization.

“These figures indicate the high burden of influenza and its substantial social and economic cost to the world,” Peter Salama, executive director of WHO’s Health Emergencies Programme, said last month. “They highlight the importance of influenza prevention for seasonal epidemics, as well as preparedness for pandemics.”

However, according to the CDC, “most people who get influenza will recover in several days to less than two weeks.” Complications range from sinus and other infections to pneumonia and organ failure.

The CDC reported that 6 percent of deaths in the United States during the week of Nov. 5 resulted from complications from pneumonia and influenza.

Kyler Baughman's family told WPXI that they do not believe he got a flu shot this year.

Then, when he got sick, “I just think he ignored it and thought it’d go away like most people,” his mother told the station.

According to his obituary, he enjoyed “motocross, reading, and going to the gym.”

That’s one reason his family wants to send this message to others: Listen to your body.

“Try and know your body. Don’t let things go,” Kyler Baughman’s father, Todd, told WPXI through tears. “Whenever you have a fever for multiple days, don’t let it go, get it taken care of.”

This post has been updated.

Read more:

CDC says flu is now widespread, and not going away anytime soon

Why this may be a bad flu season, especially around the holidays