Officials at Cook Children's Medical Center in Fort Worth said their emergency rooms have been packed with sick children.
Hospital officials said they average 400 patients per day in the emergency room. The average number of admitted children jumped from 20 to 30 in December to 40 to 50 in February.
"Our ED is running beyond full capacity and has been since December," Emergency Department Assistant Medical Director Dr. Corwin Warmink said. "But in the last few weeks we're seeing a larger number of very ill children than even during flu season."
Doctors also said there has been a 60 percent increase in the number of children who need critical care compared to last year.
"It's common for us to experience a brief interval of a lot of a certain illness," Warmink said. "We'll have flu, then RSV, then gastroenteritis illness. Right now, we're experience all three together."
Doctors suggested that parents consult with their pediatrician or an urgent care clinic and only take their children to the emergency room only in case of emergency.
NBC 5's Todd L. Davis contributed to this report.
