PHILADELPHIA (CBS) -- The number of people sick with influenza is growing and expected to get worse with germs being spread over the holiday season. Pennsylvania now has 17,000 confirmed cases of the flu, but the actual numbers are much higher because doctors say most people don't go to a doctor or get tested.
Cases in New Jersey, where there's also been one flu-related pediatric death, have tripled in the last two weeks.
The flu has killed 27 children nationwide so far this season. Along with influenza, children are also coming down with a respiratory virus known as RSV.
Four-week-old Brianna Gordon has been in intensive care for more than a week.
"I started noticing her retracting really bad and her lips started turning blue so I just called an ambulance," Brianna's mother, Kathleen Gordon, said.
RSV usually causes mild, cold-like symptoms but can be dangerous for infants and older adults.
Doctors say the bigger danger is with the flu. Activity is high around the country right now and could be nearing the peak of the season.
"We have to wait and see what happens in the coming weeks. Even if we are at peak, we still have half the flu season to go and there may be other viruses circulating after the influenza that are here right now," said Lynette Brammer, an epidemiologist with the CDC.
The CDC surveillance map shows much of the country in red, indicating flu activity is high, including in Pennsylvania and New Jersey. Delaware is one of only two states with a minimal number of cases.
Officials say this season has gotten off to an early and unusual start, with flu B viruses dominating. Those viruses tend to affect children and usually aren't seen until spring.
So far, there have been at least 6.4 million illnesses, 55,000 hospitalizations and 2,900 deaths from the flu.
"The hospitalizations and pneumonia and influenza mortality is not elevated right now. But that is what you would expect to see when you have a lot of children ill and not a lot of elderly ill," Brammer said.
More than 2 million children under the age of 5 are diagnosed with the highly-contagious virus each year. It's the No. 1 cause of pneumonia in babies.
With so many viruses out there this time of the year, doctors say it's critical to stay home when you are sick and to wash your hands frequently.
Emergency room visits and admissions have surged in recent weeks, topping the three-highest flu seasons ever recorded in New Jersey at this point of the year, according to the latest data from the New Jersey Department of Health.
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