The flu season this year has reached its peak and health professionals are now monitoring a recent wave of illnesses from a flu strain that is worse than before. Flu was reported to have spread in 48 states last week, down from 49 the week before, the Centers for Disease Control and Prevention said Friday in its latest report on this winter's flu season. The federal agency's flu forecasters think there's a 90 percent chance the flu season has reached its peak already. 

But health professionals are also monitoring an increase in illnesses from a kind of flu virus that has resulted to more hospitalizations and deaths, especially amongst the elderly. It's not unusual for several flu viruses to spread around the country at the same time, but one kind usually predominates.

This season, a milder virus has been the most common cause of flu. But for the last two weeks, more illnesses have been reported and linked to a virus that tends to cause more deaths. Last week, about 60 percent of the flu virus samples tested and it is known as Type A H3N2.

The type of H3N2 virus that will be spreading this year is still uncertain, but this led the World Health Organization to postpone its decision on which virus should go into the flu vaccine for next season. Last season, an estimated 80,000 Americans died of flu and its complications, the disease's highest death toll in at least fourty years. In the last few years, flu-related deaths have ranged from about 12,000 to 56,000, according to the CDC.

CDC officials estimate there have been somewhere around 20,000 to 30,000 deaths so far this winter, all of which are flu-related. They also think there have been around 300,000 hospitalizations and around 25 million flu illnesses in this winter season alone. 

Health officials are also encouraging the public to get their flu shots. Studies show that the vaccine was reported to be 36 percent effective at this time last year.

The vaccine must be tested and changed each year to match the most common flu virus. This year's vaccine was designed to attack four different viruses: H1N1, H3N2, Influenza A, and Influenza B. The predominate virus this year has been the H1N1 virus, with the H3N2 virus being reported more in southeastern states. Because this year's shot are focused on the viruses mentioned, those who got vaccinated are well protected.

The vaccine not only prevents the flu but it can also lessen the duration of the flu and symptom's severity. The CDC encourages people who haven't gotten the shot to get one as soon as possible. Even if you already had the flu this year, it is still best to get vaccinated. 

"Flu vaccines protect against more than one strain of the flu, and just because you were infected with one strain of the flu doesn't mean you won't get a second infection with another strain that's circulating," Dr. Amesh Adalja, an infectious disease specialist at the Johns Hopkins University Center for Health Security, told Healthline. Adalja is also a spokesperson for Theraflu.