High fever, coughing, body aches, chills, and fatigue are possible symptoms of influenza B, but they may also indicate other conditions. A healthcare professional can provide an accurate diagnosis.

Influenza, commonly known as the flu, is a respiratory infection caused by flu viruses.

There are four main types of influenza. Types A, B, and C affect humans, while influenza D mainly affects cattle.

According to the Centers for Disease Control and Prevention (CDC), types A and B are responsible for the majority of seasonal illnesses, such as in winter.

Although they’re both similar, influenza B can only pass from human to human. They can also be equally severe, challenging a previous misconception that type B tends to be a milder disease.

Influenza B accounts for just over 23% of influenza illnesses around the world.

It’s highly contagious and, in more serious cases, may lead to life threatening complications.

Keep reading to learn more about the symptoms of influenza B.

Early detection of an influenza infection can help prevent the virus from worsening and help you find the best course of treatment.

The most common symptoms of type B influenza include:

Similar to the common cold, influenza B can cause respiratory symptoms, including:

However, influenza respiratory symptoms may be more severe and can lead to other health complications.

For instance, if you have asthma, the Asthma and Allergy Foundation of America suggests the flu may worsen your symptoms and even trigger an attack.

If left untreated, or in more severe cases, influenza B may cause:

A common sign of the flu is a fever that could reach as high as 106ºF (41.1ºC). This may last up to 4 days, according to the CDC. However, it’s important to get medical attention if your fever doesn’t improve after 1 week.

In addition, you may also experience:

In rare cases, the influenza B virus may cause gastrointestinal (GI) symptoms, such as:

The authors of a 2015 review note the research is mixed on whether GI symptoms are more common in influenza B than type A.

It’s important to note that GI symptoms caused by influenza aren’t a sign of viral gastroenteritis, a viral infection commonly referred to as the stomach flu.

Several risk factors may increase the likelihood of developing complications that could require medical treatment. High risk groups include:

  • children under 5 years old, especially those younger than 2 years old
  • adults ages 65 years and older
  • people who are pregnant or up to 2 weeks postpartum
  • Native Americans (American Indians and Alaska Natives)
  • people with weakened immune systems or obesity
  • people with chronic conditions, such as diabetes, heart disease, and asthma

Research has also found that children with influenza B have a higher risk of developing severe complications or requiring hospitalization than those with influenza A.

If you experience flu symptoms and have any risk factors, get medical attention immediately. Early treatment could greatly reduce your risk of complications.

In most cases, influenza will go away on its own without medical treatment.

However, a doctor may prescribe antiviral medications if your symptoms are severe, gradually worsen, or you’re at a high risk of developing complications.

Antiviral medications for influenza include:

  • oseltamivir phosphate (Tamiflu)
  • zanamivir (Relenza)
  • peramivir (Rapivab)
  • baloxavir marboxil (Xofluza)

Getting the flu vaccine may also help prevent you from developing severe flu symptoms and any complications.

According to the CDC, the flu vaccine could help reduce your risk of developing influenza by up to 60%, especially if you’re at risk of complications. The vaccine is most effective against types B and A.

Some additional tips to help speed up your recovery may include:

  • drinking plenty of fluids, such as water, broth, and herbal tea
  • getting plenty of rest
  • taking over-the-counter medications, such as pain relievers, decongestants, and cough suppressants

The Healthline FindCare tool can provide options in your area if you need help finding a primary care doctor or pediatrician.

Learn more about treatments for the flu.

How long does influenza B last?

Influenza B may last between 2 and 8 days, according to a 2020 review.

Is flu A or B worse?

Research suggests influenza A and B may both cause serious symptoms and complications.

How contagious is influenza B?

Like influenza A, influenza B is highly contagious. If you have the flu, it’s important to practice proper hygiene to prevent transmitting the virus to someone else. This includes staying away from others, washing your hands, wearing a mask, and covering your nose and mouth when coughing or sneezing.

What is the best treatment for influenza B?

In many cases, home remedies like drinking plenty of fluids and resting is enough to help treat influenza B. However, you may require antiviral medications if you’re at risk of developing complications or you experience severe symptoms.

Type B influenza can cause you to experience symptoms more severe than a common cold.

In some cases, this infection resolves without the need for medical attention.

However, if your symptoms worsen or don’t improve after a few days, visit a doctor. They could provide a treatment plan to help prevent complications.