Influenza B: Symptoms to Watch for Explained

The United States is in the grip of an aggressive winter flu season, with the U.S. Centers for Disease Control and Prevention (CDC) having recently reported a surge in visits to doctors on a scale not seen in 15 years.

Two types of influenza viruses are responsible for seasonal flu outbreaks: Influenza A and B. Influenza A accounts for around 75 percent of all cases and tends to cause more severe illness in adults.

Influenza A is divided into subtypes based on two proteins on the virus’s surface: hemagglutinin and neuraminidase.

These lead to different combinations—with H1N1 and H3N2 presently the most common subtypes in humans—and allow influenza A to mutate more often, which is why our bodies can struggle to recognize it and fight off an infection.

Influenza A can also infect other animals, notably birds (e.g., the H5N1 subtype behind the ongoing outbreak) and pigs (such as in the 2009 H1N1 “Swine Flu” pandemic).

In contrast, influenza B can only infect humans and is less likely to mutate than the A-type counterparts. Alongside being rarer, it tends to cause more severe illness in children and often circulates later in the flu season, peaking in spring.

According to the CDC, there are two other types of flu viruses: C and D.

Influenza C typically only causes mild illness and is not thought to cause human epidemics. Influenza D, meanwhile, mainly affects cattle and other animals via spillover infections—with this type not known to cause illness in humans.

What Are The Symptoms Of Influenza B?

Both influenza A and B infections typically manifest the same broad symptoms, although they can vary case by case. Only testing by a doctor can reveal which type a patient has contracted.

Common symptoms include a cough, headaches, fatigue, muscle aches, a runny or stuffy nose and a sore throat, according to the CDC. Many patients will exhibit a fever, but this is not a diagnostic symptom.

Some patients may also suffer from diarrhea and/or vomiting, although these symptoms are more common in children than in adult patients.

“Most people who get flu will recover in a few days to less than two weeks, but some people will develop complications as a result of flu, some of which can be life-threatening and result in death,” the CDC warns on its website.

Complications are a greater risk in those aged 65 and above, young children, pregnant women and those with specific chronic medical conditions—for example, asthma, diabetes or heart disease.

On the moderate end, flu patients may go on to develop ear or sinus infections. More severe complications can include pneumonia, inflammation of the heart, brain or muscles, and multi-organ failure.

“Flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s life-threatening response to infection,” the CDC says.

Flu is also known to exacerbate the symptoms of preexisting medical conditions, like asthma and chronic heart disease.

Do Influenza Vaccines Cover A and B?

The best way to protect yourself against both types of seasonal flu and reduce an infection’s severity is to get vaccinated.

“Seasonal flu vaccines are formulated to protect against influenza viruses known to cause epidemics, including: one influenza A(H1N1) virus, one influenza A(H3N2) virus, and one influenza B/Victoria lineage virus,” the CDC explains.

“Getting a flu vaccine can protect against these viruses as well as additional influenza viruses that are antigenically similar to the viruses used to make the vaccine.”

Other sensible precautions during flu season include regularly washing one’s hands with soap and water or an alcohol-based rub, avoiding touching your eyes, nose or mouth, ensuring adequate ventilation or indoor air purification, and avoiding people who are sick.

To treat cases of flu, doctors will often prescribe antiviral medications. Those with flu are recommended to get rest, drink plenty of fluids and consider over-the-counter medications if needed to help relieve aches and fever.

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