Severe upward pressure, what you should know

Although this year's influenza season has not been as abrupt as in previous years, health experts say we're still not clear: a more serious strain now accounts for almost half of new cases and the influenza season could last until May.

A different strain of influenza virus, a "variant" virus, now accounts for 46.9% of cases, says the Center for Disease Control and Prevention. This could mean an increase in the number of diseases. Although more people have been vaccinated this year, the current vaccination protects better against the main strain, the H1N1 virus, and less well against the H3N2 viruses, according to data released Friday.

Here's what you need to know:

Strains of flu

There are four types of influenza viruses, and then subtypes. In this influenza season, health experts are mainly discovering the H1N1 and H3N2 viruses. The H3 virus is considered more serious, according to the CDC.

"It looks like we're going from a H1 wave to a H3 wave," said Lynnette Brammer, head of the CDC's influenza surveillance team, HealthDayNews reported. "There is still a lot of flu coming."

Vaccines remain the best way to prevent both strains of influenza. Brammer told HealthDayNews that this year's vaccine is 62% effective against H1N1 and 44% against H3N2.

How long does the flu season last?

Although the timing of the flu season varies each year, the CDC estimates that viruses multiply in October and November and continue until May. The flu season is usually from December to February.

sYMPTOMS

Unlike colds, flu symptoms suddenly hit – in just a few hours. Symptoms include fever, feverish chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache and fatigue. Children with flu could also vomit and have diarrhea, according to the CDC.

But here's the kicker: It's impossible to know if you have the flu just because of symptoms. The only way to ensure this is to pass a lab test, but this is not always necessary for treatment.

More: The flu is widespread in the United States with 7.3 million people sick, but experts see a season more lenient

Influenza deaths

Last week, a girl from an Ohio elementary school died the same day she was diagnosed with strep throat and flu. Although the complications of influenza are rare, they occur. This year, nearly 22,300 adults died of the flu and hundreds of thousands were hospitalized. More than 40 children died.

More: The fourth year dies the same day he is diagnosed with flu, strep throat: "Our heart is completely broken"

Signs of a deadly disease

Influenza can cause complications that can become fatal later. Examples include pneumonia; inflammation of the heart, brain or muscle tissue and multi-organ failure. Influenza can also aggravate chronic medical conditions, including asthma and chronic heart disease.

Children under 5, the elderly, pregnant women, American Indians and Alaska natives are most at risk for serious complications related to the flu, says the CDC.

If you think you have the flu and you are at high risk of developing complications, the CDC recommends consulting a doctor.

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