What is Influenza B and How is It Different From Other Forms of the Flu?

Published June 29th, 2022 by Chris Riley
Fact Checked by
Jacqueline Hensler
Medically Reviewed:
Dr. Angel Rivera

What is the Flu | Changes in the Flu | Symptoms of Influenza B

The flu, also known as influenza, is a highly contagious virus that can cause severe illness in people of all ages.

Human influenza viruses are classified into three types: A, B, and C and each type has many different strains.

The flu virus is spread through contact with respiratory secretions and can also be spread through contact with objects or surfaces that have been contaminated.

The virus can also change over time, which leads to new strains of the virus.

In this article, we will discuss what influenza B is, how it is different from other forms of the flu, and how to protect yourself from this virus.

What is the flu?

The flu is a highly contagious respiratory infection that can be caused by several different viruses.

It affects your nose, throat, and lungs and is most common in children although you can get it at any age.

The elderly, children, and those with underlying health conditions are the most vulnerable to complications with the flu which can include pneumonia, bronchitis, sinus infections, ear infections, and in rare circumstances even death.

There are seasonal flu epidemics that cause flu cases in the United States to spike during flu season which lasts from October through May, often peaking in December through February.

The Centers for Disease Control and Prevention (CDC) estimate that approximately 8% of the United States population gets the flu every year although the number can vary from year to year.

The flu is different from the common cold in that its symptoms are typically more severe.

How does the flu virus spread?

Flu viruses are usually spread from person to person by respiratory droplets that are made when you cough, sneeze, or talk.

These droplets can land in the mouths, eyes, or noses of people who happen to be in close proximity to the infected individual.

In rare instances, you may also get the flu by touching a contaminated surface that has the flu virus on it and then touching your own mouth, eyes, or nose.

You can also spread the flu virus to others even if you do not have any symptoms yourself, which is called being asymptomatic, and typically you are asymptomatic for a day before your symptoms start although it is possible to never show any symptoms.

If you have the flu, you are most contagious in the first three to four days after your illness begins but can still spread the virus for up to a week after you start feeling sick.

How do flu viruses change?

Flu viruses are constantly changing and the main way that flu viruses change is through a process called antigenic drift which is when the virus mutates slightly and then changes the surface proteins of the virus called antigens.

These proteins are what your immune system uses to recognize and trigger a response to fight the virus.

Antigenic drift happens slowly over time and is the reason why you can get the flu more than once in your lifetime as well as why there is a new flu vaccine each year that is designed to protect against the most common strains of the virus that are expected to circulate during that particular flu season.

Another way flu viruses change or mutate is through antigenic shift which is a much more drastic change and happens when the virus swaps genes with another flu virus.

An antigenic shift can happen between two different animal flu viruses or between an animal and human flu virus.

These types of mutations are what cause pandemics, or global epidemics, like the 1918 Spanish Flu pandemic that killed an estimated 50-100 million people worldwide.

What are the different types of influenza viruses?

There are four different types of influenza virus: A, B, C, and D.

Influenza A and B viruses are the most common and are responsible for the vast majority of flu cases each year.

Both humans and animals can get infected with influenza A viruses while only humans can get infected with influenza B viruses.

Influenza C viruses infect both humans and animals, specifically pigs, but usually only cause a mild respiratory illness in humans and do not cause large outbreaks.

Influenza D viruses primarily affect cattle but have been known to infect pigs as well but have never been known to infect humans.

test for influenza a or influenza b image

What are the symptoms of influenza B?

The symptoms of influenza type B are similar to the symptoms of other types of flu and have respiratory symptoms, body symptoms, and stomach symptoms.

The most common symptoms of influenza B virus include:

  • Fever
  • Chills
  • Cough
  • Sore throat
  • Runny nose or stuffy nose
  • Congestion
  • Body aches or muscle aches
  • Headache
  • Tiredness or fatigue
  • Vomiting (most common in children)
  • Diarrhea (most common in children)
  • Abdominal pain
  • Lack of appetite
  • General weakness

Symptoms can range from mild to severe and typically last for about a week.

The flu can also lead to serious complications like pneumonia, bronchitis, sinus infections, ear infections, sepsis, respiratory infections, and inflammation of the heart also known as myocarditis.

It can also lead to hospitalization and in severe cases can even be fatal.

What are the treatment options for influenza B?

If you have influenza B, it is important to see your doctor as soon as possible so that he or she can prescribe an antiviral medication that is most effective against the specific strain of virus that you have.

These antiviral drugs can help to shorten the duration of your illness and make your symptoms less severe but they are most effective when taken within 48 hours of when your symptoms first start.

You also need to drink plenty of fluids, get rest, and stay away from others as much as possible to prevent the spread of the virus.

You are no longer contagious when your fever has gone away without the use of medication for 24 hours.

Are there ways to prevent the spread of the flu?

Yes, there are a few different things that you can do to help prevent the spread of influenza B and other types of flu.

The best way to prevent the flu is by getting vaccinated each year with the seasonal flu vaccine (flu shot).

The flu vaccine is designed to protect against the most common strains of the virus that are expected to circulate during that particular flu season.

You can also help to prevent the spread of the flu by washing your hands regularly, avoiding close contact with people who are sick, and disinfecting surfaces that are frequently touched like door handles, light switches, and countertops. If you cough, remember to cough into your elbow, sleeve, or tissue to help prevent the spread of germs.

Do not cough into your hands as you may forget to wash them and contaminate other surfaces.


The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs.

It is typically spread through coughing or sneezing, close contact with someone who is sick, or touching surfaces that have been contaminated with the virus.

The flu can cause mild to severe illness and in some cases can lead to hospitalization or even death. Influenza B is one of the most common types of influenza viruses and is responsible for causing a large number of flu cases each year. The symptoms of influenza B are similar to the symptoms of other types of flu and are listed above. If you have influenza B it is important to see your doctor as soon as possible so that they can prescribe the antiviral medication that is most effective. If you have any more questions regarding the flu or influenza B, please talk to your doctor or health care provider.

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