A father is warning about how serious the flu can be, especially for children, as his 10-year-old son remains hospitalized with the virus.
Cory Tamborelli, from Ramona, California -- about 34 miles northeast of San Diego -- said his son, Tristan, first started experiencing flu symptoms about a week and a half ago.
'A fever and a little bit of a runny nose," he told ABC News local affiliate KGTV.
MORE: Some schools close to stem flu outbreaks -- but is it a good long-term solution?However, the young boy's condition rapidly deteriorated and within 48 hours, Tristan was unresponsive.
"He was limp, couldn't move, couldn't talk. It was the most scared I've ever been in my life," Tamborelli said.
Tristan was life-flighted to Rady Children's Hospital in San Diego, where he tested positive for two strains of flu, according to an update from his aunt, Sara Presley Scott.
Doctors discovered that Tristan's liver and kidney were failing. He was rushed to the pediatric intensive care unit, where he was sedated and placed on a ventilator.
His aunt said he needed to be placed on dialysis to help support his non-functioning kidney.
"It was so bad. I was scared he wasn't going to make it. You feel helpless," Tamborelli said. "Nothing you can do."
Hospitals across the country have been reporting that they are at capacity or near capacity as the flu season has started earlier than usual.
According to the Centers for Disease Control and Prevention, some children are at higher risk of developing flu-related complications including infants, those up to age 5, American Indian/Alaskan Native children, and those up to age 18 with chronic health problems.
MORE: Health officials make urgent push for flu and COVID shots as hospitals feel the strainTristan falls into that latter category. Tamborelli told KGTV that his son suffered a stroke as an infant and, as a result, has several underlying conditions including epilepsy and a blood clotting disorder.
"Each year, millions of children get sick with seasonal flu, thousands of children are hospitalized and some children die from flu," according to the CDC.
Currently, children age 4 and under are being hospitalized at a rate of 42.3 per 100,000 and children between ages 5 and 17 at a rate of 17.9 per 100,000 -- the highest rates recorded since the 2009-10 season, which was the year of the swine flu outbreak, CDC data shows.
Additionally, at least 21 pediatric deaths have been recorded so far this season.
Tristan has since come off the ventilator and his condition is starting to improve, although doctors told his family it will likely be a long road to recovery.
Now, Tamborelli is urging families to make sure their children are vaccinated as the U.S. heads into the colder weather months.
According to CDC data, about 42.5% of all children have been vaccinated as of the week ending Nov. 26, the latest date for which data is available.
MORE: Suffering from flu, RSV or COVID-19? How you can tell the differenceThis is similar to the 40.9% of children who were vaccinated this time last year but less than the 46.9% who were in 2020.
This year, a CDC study -- conducted alongside other experts -- found that flu shots were 75% effective against life-threatening influenza.
Tamborelli said Tristan's flu shot from his pediatrician was delayed last month but is advising other parents not to delay and to be on the lookout for flu symptoms.
"Keep an eye out. If they get sick, and you're not sure, take them to the hospital," he told KGTV. "I'd hate to have anyone else go through this."