▶ Watch Video: Doctors fear a triple threat of viruses this winter: COVID-19, RSV and flu

California health officials are warning families to take precautions against the flu and Respiratory Syncytial Virus, known as RSV, after a child under the age of 5 died after contracting the illnesses. 

The California Department of Health reported the child’s death on Monday, saying that no identifying details of the child would be released to protect the family’s privacy. It was the first reported death of this nature and age range this winter season, officials said. 

“Young children are most vulnerable to severe complications from RSV and the flu, especially if they have underlying medical conditions or were born premature,” officials said. 

The child’s death “serves as a stark reminder,” said Dr. Tomás Aragón, state public health officer and department of health director.

“Respiratory viruses can be deadly, especially in very young children and infants,” Aragón said. “We are entering a busy winter virus season – with RSV, flu and COVID-19 spreading – and urge parents and guardians to vaccinate their children as soon as possible against flu and COVID-19.”

Aragón also urged people to follow “basic prevention tips” – washing hands frequently, wearing a mask and staying home when sick. 

California has seen an increase in positive antigen RSV tests since August, hitting a 28.7% positivity rate by mid-October, according to data from the Centers for Disease Control and Prevention. Nationally around the same time, there was a 17% PCR positivity rate and a slightly declining roughly 15% antigen positivity rate, CDC data shows. That data was last reviewed by the CDC on November 2. 

The rapidly spreading illness prompted Orange County, California, to issue a state of emergency on Oct. 31, with officials saying the spread has caused “record numbers of pediatric hospitalizations and daily emergency room visits.” 

Every year, RSV causes about 58,000 hospitalizations in children under 5, according to the National Institute of Allergy and Infectious Diseases, and causes about 14,000 deaths among older adults. 

The flu tends to be more widespread. This year, five pediatric deaths caused by the flu have been reported to the CDC. And just last week, more than 6,400 people were hospitalized with the flu nationwide. 

Doctors elsewhere are concerned by this triple threat of viruses. On Monday, Dr. Dyan Hes, the medical director at Gramercy Pediatrics in New York, told CBS News that RSV tends to just be like a “common cold” in most kids, but can cause respiratory distress in some. 

The symptoms of RSV tend to be similar to that of the flu and COVID-19, she said. Any concerns, she said, should be addressed by a pediatrician. 

“The problem is that these kids have been masked for two years, so they’re just getting sick back-to-back,” she said.

The combination of illnesses has become known as a “tripledemic” that has already filled up many pediatric ICUs around the country. In many parts of the nation, these ICUs are full, CBS News medical contributor Dr. David Agus said earlier this month, adding that many of those hospitalizations are related to the flu and RSV.