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What is influenza B?

Understanding Influenza B: The Lesser Known Virus

, by AussiePharmaDirect, 9 min reading time

Influenza, or simply “the flu”, is a common respiratory illness that can be found worldwide. There are four types of influenza viruses: Influenza A, Influenza B, Influenza C, and Influenza D. Among these types, Influenza A and Influenza B are the most common and frequently encountered. You can't escape it; chances are, you've had a not-so-pleasant encounter with it at some point in your life. While it may not generate the same level of global impact as Influenza A, it remains an important player in seasonal flu activity.

In this blog, we will delve deeper into what influenza B is, exploring its characteristics, transmission patterns, impact on public health and some tips on prevention and improving our resilience against the flu.

What is influenza B?

Unlike Influenza A, Influenza B does not have subtypes but is classified into distinct lineages, such as Yamagata and Victoria. It is known to cause localised outbreaks and can lead to a significant number of flu cases, albeit on a smaller scale compared to Influenza A.

Regarding the ecology of the virus, Influenza B has a complex interaction with its natural hosts. Influenza B is primarily associated with human-to-human transmission and exhibits seasonal patterns of activity. In addition to humans, some evidence suggests that Influenza B viruses can infect seals and ferrets, although their significance in the overall ecology of the virus remains relatively limited compared to the human population. Certain subtypes of Influenza A viruses, on the other hand,  have occasionally been transmitted from animals to humans. This is known as zoonotic transmission and has occurred in cases such as avian influenza (H5N1) or the swine flu (H1N1). 

In temperate regions, Influenza B typically causes outbreaks during the winter months, similar to other respiratory viruses. The virus can persist and spread more easily in colder and drier conditions, allowing it to thrive during the winter season.

Is influenza B contagious?

Just like its other influenza siblings, it is a highly contagious respiratory virus that can spread easily from person to person. When an individual infected with influenza B coughs, sneezes, or talks, they release respiratory droplets containing the virus into the air. These droplets can be inhaled by nearby individuals, leading to the transmission of the virus.

In addition to inhalation, influenza B can also spread through direct contact. If an infected person has the virus on their hands and touches surfaces or objects, they can contaminate those surfaces. When another person touches the contaminated surface and then touches their mouth, nose, or eyes, they can introduce the virus into their own body, potentially causing an infection.

So, how long are you contagious with the flu? Influenza B is most contagious during the first few days of illness when symptoms are most severe. However, infected individuals can still spread the virus before symptoms appear or even if they have mild symptoms.

Influenza B symptoms

Common symptoms of influenza B include:

  • Fever: A sudden onset of high body temperature, often above 100.4°F (38°C).
  • Cough: A persistent, dry or productive cough that may worsen over time.
  • Sore throat: Irritation or pain in the throat, often accompanied by difficulty swallowing.
  • Fatigue: Profound tiredness and weakness that can last for several weeks.
  • Body aches: Generalised muscle or body aches, often described as feeling sore or tender.
  • Headache: A persistent, throbbing pain in the head.
  • Chills: Shivering or experiencing cold sensations, often accompanied by fever.
  • Runny or stuffy nose: Excessive nasal discharge or congestion.
  • Sneezing: Frequent, involuntary expulsion of air from the nose and mouth.
  • Watery eyes: Excessive tear production or eye irritation.
  • Respiratory symptoms: Some individuals may experience shortness of breath or chest discomfort.

These symptoms can vary in intensity and may overlap with other respiratory illnesses. Influenza B symptoms can resemble those of the common cold, but the flu tends to cause more severe symptoms and rapid onset of illness.

Health complications from influenza B

Influenza B can lead to various health complications, especially in individuals who are more vulnerable or have weakened immune systems. Some common complications associated with influenza B include:

  • Pneumonia: Influenza can increase the risk of developing bacterial or viral pneumonia, which is an infection in the lungs that can cause severe respiratory symptoms.
  • Bronchitis: Influenza B infection can lead to bronchitis, an inflammation of the bronchial tubes that carry air to and from the lungs. It can cause coughing, chest discomfort, and excessive mucus production.
  • Sinusitis: In some cases, influenza B can result in sinusitis, which is inflammation and infection of the sinuses, causing symptoms such as facial pain, pressure, and nasal congestion.
  • Ear infections: Children with influenza B may be prone to developing ear infections, such as otitis media, which can cause ear pain, fluid buildup, and temporary hearing loss.
  • Asthma exacerbation: In individuals with asthma, influenza B can trigger or worsen asthma symptoms, leading to increased wheezing, coughing, and shortness of breath.
  • Myositis: In rare instances, influenza B infection can result in myositis, which is inflammation of the muscles, causing muscle pain, weakness, and swelling.
  • Cardiac complications: Influenza B can increase the risk of cardiovascular complications, such as myocarditis (inflammation of the heart muscle) or exacerbation of existing heart conditions.
  • Neurological complications: In rare cases, influenza B can cause neurological complications, including encephalitis (inflammation of the brain), seizures, and Guillain-Barré syndrome (a rare autoimmune disorder affecting the nerves).

Exacerbation of underlying conditions: Influenza B infection can worsen chronic conditions, such as diabetes, respiratory diseases, or immune disorders.

Flu symptoms for 3 weeks now. What does that mean?

Experiencing flu-like symptoms for an extended duration, such as 3 weeks, may raise concerns and indicate the possibility of complications or an underlying condition. While the typical duration of uncomplicated influenza is usually around one to two weeks, the severity and duration of symptoms can vary among individuals.

It's important to monitor your symptoms closely and seek medical advice if:

  1. Symptoms worsen or do not improve after a few weeks.
  2. New or severe symptoms develop, such as persistent high fever, chest pain, shortness of breath, or significant fatigue.
  3. You belong to a high-risk group, such as the elderly, young children, pregnant women, or individuals with underlying health conditions.

Can you have influenza A and B at the same time?

It is possible to have both influenza A and influenza B at the same time. During flu season, multiple strains of influenza viruses can circulate in the community. It is not uncommon for individuals to be infected with more than one strain or type of influenza virus simultaneously. This co-infection can occur if a person is exposed to multiple strains of influenza viruses at the same time or during separate instances of exposure.

There are antigen test kits available that you can use as a preliminary measure to get an indication of whether you may have the virus. These test kits are designed for home use and can detect the presence of flu antigens in respiratory samples such as nasal swabs

Influenza B treatment and prevention

Once diagnosed with influenza B, treatment options are available to help manage the illness. Antiviral medications, such as oseltamivir (Tamiflu), zanamivir (Relenza), and peramivir (Rapivab), can be prescribed by healthcare professionals. These medications work by inhibiting the replication of the influenza virus, thereby reducing the duration and severity of symptoms.

These antiviral medications are most effective when initiated early in the course of the illness, ideally within the first 48 hours of symptom onset. They can help shorten the duration of symptoms by a day or two and potentially reduce the risk of complications.

In addition to antiviral treatment, supportive care is crucial in managing influenza B symptoms. This includes getting plenty of rest, staying hydrated, using over-the-counter pain relievers (under medical guidance), and implementing measures to alleviate symptoms such as fever, cough, and congestion.

Prevention through vaccination is the most effective strategy to reduce the risk of influenza B infection. Annual flu vaccines are designed to provide protection against the most prevalent strains of influenza viruses expected to circulate in a given flu season. You can schedule a flu vaccination for yourself by contacting your healthcare provider, local clinic, or pharmacy to inquire about availability and appointment options. It is recommended to get vaccinated before the flu season starts, as it takes about two weeks for the vaccine to provide optimal protection.


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