Healthy Living

Influenza B: What You Need to Know

Influenza B virus


Influenza, also commonly called as the flu, is a highly contagious respiratory infection caused by viruses, particularly influenza A or influenza B. These viruses usually infect the throat, nose, and lungs. Although the flu causes mild symptoms in most people, it can also cause severe illness and even death in high-risk groups, such as infants, young children, and the elderly. The flu frequently appears during winter and early spring. 

Each year, different strains of the flu are circulated. The flu frequently appears during winter and early spring.

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Influenza B

Influenza B is one of the subtypes of the influenza virus. This virus tends to sporadically occur and causes an epidemic and not pandemic. It is very contagious, especially in patients who are very young, old, or with serious medical conditions. Influenza B can also cause severe symptoms. The severity may vary, but the symptoms commonly involved are constitutional and respiratory. 

Although most flu symptoms are the same, influenza viruses can mutate and different strains can be produced. Since the virus frequently mutates, regular flu vaccinations are needed to have protection against new viral strains. Before, influenza B was considered to only infect humans, but according to new scientific data, seals (harbor seals and gray seals) can also be infected. 

Typically, there is one strain of influenza B included in the seasonal flu vaccine, aside from the two strains of influenza A. Moreover, the influenza B virus usually evolves much slowly at a rate of 2-3 times slower than the type A strain. Influenza B viruses usually infect different age groups. However, when compared to influenza A viruses, influenza B tends to be more common in children than adults. 


When someone who has the flu sneezes, coughs, or talks, flu viruses travel through air droplets. You can get the flu virus when you directly inhale these infected droplets or when you pick up the viruses from contaminated objects, such as remote controls, door knobs, or telephone. These viruses can enter your mouth, nose, or eyes. 

Flu viruses tend to constantly change or mutate, which is why new strains of influenza viruses regularly appear. People who have had the flu usually develop antibodies to fight off that specific viral strain. In cases when they get infected again by a similar flu virus, the antibodies produced by their body against that strain may help prevent the infection or reduce the severity of their illness. However, such antibodies may not provide protection against other subtypes of influenza, since they are immunologically different from the ones they had before. 


At first, you may feel that you have a cold since you have its common symptoms, such as sneezing, runny nose, and a sore throat. However, colds tend to gradually develop while the flu usually comes on suddenly. You may feel weak for a few days when you have a cold, but when you have the flu, the symptoms usually make you feel very sick for several days to weeks. When you have the flu, other serious medical conditions may also arise such as pneumonia.

Below are the most common signs and symptoms of the flu:

  • High fever (more than 38 degrees Celsius or 100.4 degrees Fahrenheit)
  • Weakness and fatigue
  • Sore throat
  • Nasal congestion
  • Dry and persistent coughing
  • Headache
  • Body aches (particularly in the arms, legs, and back)
  • Periods of chills and sweats

Risk Factors

Some of the factors that may increase a person's risk of getting flu viruses include:

  • Age: Young children and adults who are older than 50 are more prone to developing complications from influenza. 
  • Being Pregnant: Pregnant women are more likely to develop complications when they get the flu. They are more often at risk when they reach their second and third trimesters. After childbirth, some women also have an increased risk of developing flu-related complications. 
  • Chronic Diseases and Conditions: People who have chronic health problems, such as heart disease, diabetes, or asthma are more prone to developing complications from the flu. 
  • Working and Living Conditions: People who work in military barracks and nursing homes, as well as those who live in crowded areas, have an increased risk of developing influenza. 
  • Obesity: Complications from the flu may be often experienced by people who have a body mass index (BMI) of 40 and above. 
  • Low Immune Function: People who have a weakened immune system due to cancer therapy, corticosteroid therapy, or HIV/AIDS are more likely to develop complications from the flu. 

Complications of Influenza B

  • Bacterial Pneumonia - This lung infection is the most common complication of influenza B. The flu virus may damage the surface of the lungs and restrict the airway, thereby increasing people’s risk of developing bacterial infections in the lungs.

    When a person develops bacterial pneumonia, harmful bacteria tend to rapidly grow and multiply in the respiratory tract. This bacterial invasion can cause inflammation, fluid, and swelling of the lungs’ air sacs. If the lungs are filled with fluid, people usually have breathing difficulties along with coughing, high fever, and chest pain

  • Encephalitis - Encephalitis is the medical term for swelling or inflammation of the brain. This rare complication occurs when the brain is inflamed due to viral infections, including influenza B. Encephalitis can also happen when there is an overstimulation of a person’s immune function due to the presence of the flu virus. The initial signs of encephalitis are headache and fever. These signs are then followed by confusion, drowsiness, seizures, or coma. The elderly and young children are more prone to developing this complication. 
  • Myositis - This is the term used when referring to progressive or chronic muscle inflammation. In this condition, movements become difficult and the muscles become weak. The symptoms usually last for 1-5 days. Children are more likely to be affected by this complication.
  • Reye's Syndrome - This is a rare medical condition that affects the liver and brain. It often occurs following a recent viral infection, such as the flu, in children. It causes confusion, vomiting, delirium, and nausea. Children who might have taken aspirin for the infection increases their risk of developing the condition. 
  • Other Complications - Sinus infection, ear infection, and bronchitis.


Influenza B is a viral infection, so treating it using antibiotics won’t work. Antibiotics are usually effective when it comes to treating bacterial infections. Instead of antibiotics, antiviral medications are given when it comes to flu. Treatment using antivirals can help reduce the duration of the flu and its complications.  

Antiviral medications can help stop viral replication and may reduce complications. Most healthy individuals who have the flu do not need antivirals. Such treatment should only be given to high-risk groups and those who have serious health conditions. Antivirals are ideally administered at the onset of symptoms, which is usually within 48 hours. Antiviral medications include:

To help relieve nasal symptoms, the following medications may be given:

  • Decongestants (phenylephrine, oxymetazoline, or pseudoephedrine)
  • Antihistamines (chlorpheniramine, diphenhydramine, clemastine, or doxylamine)
  • Ipratropium bromide nasal spray (Atrovent)

When it comes to fever and body aches:

  • Acetaminophen (Tylenol)
  • Naproxen (Aleve)
  • Ibuprofen (Advil, Motrin)

Always consult a doctor before taking these drugs since naproxen and ibuprofen have side effects, such as stomach bleeding and high blood pressure that can affect kidney function. Acetaminophen can also affect the liver if not taken in correct dosages. 

The best defense against the flu is to receive annual vaccinations.