Influenza B: What You Need to Know

Most flu cases—around 70% of reported cases—are influenza A. However, the influenza B virus is the cause of the next most common type of flu.

Influenza can affect humans and animals, but influenza type B is one type of the illness that causes symptoms in humans only. Also, if you're wondering which is worse—influenza A or B—type A is responsible for more severe illnesses. Read on to learn about influenza type B, including symptoms, treatment, and more.

What Is Influenza B?

Influenza B is a type of influenza known to cause seasonal epidemics along with influenza A. This type of influenza normally affects people. The viruses for this type primarily exist in humans.

Difference Between Influenza A and B

Influenza A and B viruses are each divided into smaller categories. Influenza A viruses fall under different subtypes based on two specific proteins, hemagglutinin (H) and neuraminidase (N). Influenza B viruses, however, are classified into two lineages: B/Yamagata and B/Victoria.

Influenza A also tends to cause worse symptoms than influenza B. Influenza B viruses also change slower genetically compared to influenza A viruses. However, one study did find that infections from Influenza B and Influenza A can be just as severe.

Influenza B Symptoms

The symptoms of influenza B are similar to those of other strains of influenza A. They include:

• Cough
  
• Fatigue
• Fever—though everyone does not have a fever—or chills
• Gastrointestinal symptoms like vomiting and diarrhea—which are more common in children
• Headaches
• Muscle or body aches
• Runny nose
• Sore throat
  

What Causes Influenza B?

The influenza viruses from the Victoria and Yamagata lineages, which can circulate at the same time, cause influenza B. Viruses coming from the Victoria lineage tend to affect younger people. Those from the Yamagata lineage often affect older individuals.

How Is Influenza B Diagnosed?

A healthcare provider can diagnose the flu in general based on the information you give them about your symptoms and if the flu is prevalent in your area. A provider can also use one of the following tests for flu diagnosis:

• Molecular tests: Tests that provide rapid and more accurate results to determine if you have the flu. They may include a provider getting a nose or mouth fluid sample to send to a lab for testing.
• Rapid influenza antigen tests: A provider will use these tests to get a flu diagnosis confirmation in less than an hour, though the tests are less accurate than molecular tests.

Treatments for Influenza B

When treating the flu, the goal is to help reduce and resolve symptoms of the flu. Treatment options include self-care for milder cases or antiviral medications in more severe cases.

Self-Care

You can usually treat the flu with at-home treatments and actions. They include:

• Drinking plenty of liquids
• Getting a lot of rest
• Taking fever-reducing medications like acetaminophen or over-the-counter cold medicines
• Using cough drops or throat sprays for a sore throat

Antiviral Medications

Antiviral medications help cut down the time you are sick with the flu. These medications aren't necessary for all flu cases. A provider may only prescribe them if you become very sick while you have the flu or have a higher risk of flu-related complications.

How To Prevent Influenza B

The best way to prevent the flu—both influenza A and B—is by getting the flu vaccine. The recommendation is for individuals 6 months or older to get vaccinated against the flu. Children 8 and younger would need two doses during flu season, while people 9 and older would only need one dose.

You can also prevent the flu by:

• Keeping your distance if you or someone else is sick
• Staying home when you are sick with the flu
• Washing your hands with soap and water or using hand sanitizer with 60% alcohol

Complications

The main complication of the flu is pneumonia. Other possible complications include brain infection, meningitis, and seizures. Some people have a higher risk of developing flu-related complications, including people who:

• Are more than 3 months pregnant
• Are younger than 2 years old or 65 years and older
• Have chronic heart, kidney, or lung conditions
• Have diabetes or a weakened immune system
• Live in a long-term care facility
  

When to Contact a Healthcare Provider

You don't have to see a healthcare provider for flu symptoms, regardless of the type of flu virus causing them, unless you are at risk of developing complications. You'll also want to see a provider if flu symptoms worsen and don't improve with home care treatments.

A Quick Review

Influenza B is a type of influenza caused by viruses from the Victoria or Yamagata lineages. Symptoms of this flu type are similar to other strains of the flu, though they are mild in comparison to symptoms of influenza A. The flu is both treatable and preventable. However, you should see a healthcare provider if you have problems with treatment and symptoms or may be at risk for complications.