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influenza A vs B

Influenza A vs. Influenza B: What are the Differences?

, by AussiePharmaDirect, 8 min reading time

Influenza A and Influenza B, two prevalent viral infections, have gained quite a reputation over the years, owing to their ability to cause widespread infections and impact many people globally. According to the WHO, seasonal influenza (generally known as the flu) infects millions of people worldwide each year. The estimated range of global influenza cases is between 1 billion and 1.5 billion!

The impact of influenza extends beyond mere infection rates. Each year, seasonal influenza is responsible for causing severe illness in approximately 3 to 5 million people and results in 290,000 to 650,000 respiratory-related deaths. These figures reflect the toll that influenza can take on vulnerable individuals, such as the elderly, young children, pregnant women, and those with underlying health conditions.

Despite belonging to the same Orthomyxoviridae family, influenza A and influenza B exhibit distinct characteristics that set them apart. In this blog, we’ll unravel the mysteries and shed light on the contrasting features, clinical implications, and epidemiological factors that make each of these viruses stand out.

What are the common symptoms of the flu?

Influenza A and influenza B share many similarities in terms of symptoms. Both types of viruses typically manifest as respiratory illnesses with a rapid onset. These symptoms can range from mild to severe, depending on the individual and the specific strain of the virus. Below are the hallmark symptoms:

  • Fever 
  • Cough
  • Stuffy or runny nose
  • Sore throat
  • Fatigue or weakness
  • Body aches
  • Headaches 
  • Chills
  • Chest discomfort or tightness
  • Shortness of breath
  • Vomiting or diarrhoea (more frequently observed in paediatric cases compared to adults)

Complications and severity

When it comes to the flu, there's good news and challenging news. The good news is that the majority of people who contract the flu will recover without complications by practising self-care and utilising simple flu remedies.

However, there are some individuals who are at a higher risk of developing severe complications, particularly in certain high-risk groups. These complications include:

  • Pneumonia
  • Bronchitis
  • Sinus and ear infections
  • Worsening of existing health conditions
  • Inflammation of the heart (myocarditis), brain (encephalitis) or muscle tissues (myositis, rhabdomyolysis)
  • Multi-organ failure
  • Sepsis 

Emergency signs to watch out for

Recognising the emergency signs of influenza and seeking immediate medical attention can be crucial in potentially saving lives. It's important to be vigilant for certain warning signs that indicate a need for urgent medical care. Prompt recognition and treatment of these emergency signs can help prevent severe complications and even fatalities.

For both children and adults, the following emergency signs associated with influenza should be taken seriously:

  • Difficulty breathing or shortness of breath: Difficulty breathing can be a sign of pneumonia, bronchitis, or other respiratory complications.
  • Cyanosis or bluish lips/face: Indicates a lack of oxygen in the blood. This is a severe symptom that warrants immediate medical attention.
  • Severe or persistent vomiting: While vomiting can be a symptom of influenza, severe or persistent vomiting, especially in children, should be evaluated promptly. Excessive vomiting can lead to dehydration, electrolyte imbalances, and other complications.
  • Confusion or altered mental status: Influenza can sometimes cause neurological complications, leading to confusion, disorientation, or changes in mental status. These signs may indicate encephalitis or other serious conditions.

Severe dehydration: Flu-related symptoms such as fever, sweating, and respiratory issues can contribute to fluid loss. If you or your child experience signs of severe dehydration, including decreased urination, dry mouth, dizziness, or extreme thirst, it's crucial to seek immediate medical attention.

So, what’s the main difference between Influenza A and B? Which is worse - Influenza A or B?

The "worseness" of influenza A or B is not solely determined by the virus type, but rather by various factors such as the specific strain, individual health status, and any pre-existing medical conditions. Influenza A and influenza B viruses exhibit distinct patterns in terms of their epidemiology, prevalence, and seasonal activity. 

1. Epidemiology

Influenza A viruses have a broader range of hosts, including humans, birds, and some other animal species. They are known to cause more severe outbreaks and pandemics. It has a higher propensity for genetic mutations, leading to the emergence of new strains and subtypes. The subtypes are categorised based on their surface proteins: hemagglutinin (H) and neuraminidase (N), to which the most notable subtypes of influenza A include H1N1 and H3N2.

On the other hand, influenza B viruses primarily infect humans and cause milder illness compared to influenza A. The viruses are not classified into subtypes but are further divided into different lineages, including Victoria and Yamagata. Influenza B viruses are less likely to cause large-scale outbreaks or pandemics. However, this does not mean that influenza B should be taken lightly, as it can still lead to significant illness, especially in vulnerable populations.

2. Prevalence and seasonal activity

Generally, influenza A viruses are more commonly associated with large-scale seasonal outbreaks and epidemics, whereas influenza B viruses often cause more localised outbreaks. According to a study, it has been observed that influenza A infections account for approximately 75 percent of confirmed seasonal influenza infections, while influenza B infections make up the remaining 25 percent.

In temperate regions, including North America and Europe, influenza activity typically follows a distinct seasonal pattern. Influenza A and B viruses tend to peak during the winter months, typically between December and February in the Northern Hemisphere. The flu season in Australia typically occurs from June to August, aligning with the Southern Hemisphere.

The reasons behind the varying patterns of influenza A and B activity are multifactorial. One major factor is antigenic drift, the gradual genetic changes that occur in both influenza A and B viruses over time. These changes make it necessary to update the flu vaccine annually to ensure its effectiveness against the prevalent strains.

Treatment options

The treatment of influenza typically involves a combination of antiviral medications and supportive care aimed at relieving symptoms and promoting recovery. The general approach to treatment is similar for both influenza A and B:

  1. Antiviral medications: Antiviral drugs can help reduce the severity and duration of influenza symptoms when taken early in the illness. The two main classes of antiviral drugs used for treating influenza are neuraminidase inhibitors and adamantanes. Neuraminidase inhibitors, such as Tamiflu and Relenza, are particularly effective against both influenza A and B viruses.
  2. Supportive care: When you're feeling under the weather, some good old-fashioned TLC can go a long way. Give your body a rest and keep the fluids flowing like a champion for hydration. Need some relief from those nagging symptoms? Reach for over-the-counter pain relievers. And let’s not forget adding some steamy ambiance to your flu battle. A humidifier or a steamy shower can help ease your nasal congestion and make breathing a breeze!
  3. Supplements: Supplements are not typically considered primary preventive treatment for influenza but they’ll lend a helping hand in supporting your overall health and immune system, and it’s easier to buy supplements online and in stores around Australia.

Flu vaccination: Flu vaccines are specifically designed to target the prevalent strains of influenza viruses anticipated for each flu season. By receiving the vaccine, your immune system learns to recognise and defend against these strains, providing a shield of protection. To benefit from flu vaccination, consult with your healthcare provider or you can book your flu shot at vaccination clinics around Australia.

Influenza A vs B


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