FRIDAY, Jan. 22, 2016 (HealthDay News) -- Halfway through this year's rather mild flu season, disease activity is still increasing, albeit slowly, a U.S. health official said Friday.
"Activity is continuing to increase; it looks a little bit more impressive this week," said Lynnette Brammer, an epidemiologist with the U.S. Centers for Disease Control and Prevention.
So far, this flu season has been much milder and kicked in later than last year. By this time last year, flu was already severe and sending thousands of older Americans to the hospital, Brammer said. In fact, "by this time last year we had peaked and were coming down," she noted.
Unlike last year, this season the H1N1 strain of the flu is the most common circulating strain, replacing the H3N2 strain, Brammer said. "But H3N2 is still hanging in there, it's not going away," she said. "We've got a little bit of everything out there."
Both of these strains, and another besides, are included in the current flu vaccine, Brammer said, making this year's flu shot a better match than the one from the 2014-2015 season.
As to the illness' reach, "we are seeing flu everywhere, but it is most active still in the Southeast, Arizona and the West Coast," Brammer said.
Worse activity could come, she added.
"I would be very shocked if we didn't see flu activity increase in the next couple of weeks," Brammer said. And with flu still at moderate levels but increasing, it's a great time to get vaccinated, she said, noting that plenty of vaccine is still available.
Milder weather may be one factor delaying this year's flu, Brammer said. But it's only one factor of many that affect how flu spreads. Other factors include how many people are immune because they've been vaccinated and the low number of people with flu who could infect others.
In a typical flu season, flu complications -- including pneumonia -- send more than 200,000 Americans to the hospital. Death rates linked to flu vary annually, but have gone as high as 49,000 deaths in a year, the CDC says.
Virtually everyone older than 6 months of age is advised to get a flu shot. The exceptions are people with life-threatening allergies to the flu vaccine or any ingredient in the vaccine, according to the CDC.
Pregnant women are at high risk and should get vaccinated. Women with newborns also need to get their flu shot to help protect their infants, who can't be vaccinated until they are at least 6 months old. Also at risk are seniors and people with chronic health problems, such as lung and heart disease, the CDC says.
How effective the vaccine is in preventing the flu depends on how good a match it is to the strains of flu virus circulating that year. Most years, the vaccine is between 40 percent and 60 percent effective, according to the CDC.
For more on flu, visit the U.S. Centers for Disease Control and Prevention.