Influenza A or B? Know the Differences this Flu Season

Credit: Monstar Studio/Adobe Stock

As the calendar turned to February, many across the US are dealing with or know somebody dealing with the voracity of this year’s influenza season. From children to older adults and everyone in between, this year’s influenza season is proving to be one of the most daunting in recent memory.

With this in mind, understanding the key differences between influenza A and influenza B can help individuals better recognize symptoms, seek timely treatment, and reduce the spread of the virus. While both types cause seasonal flu and share many similarities, there are important distinctions in their behavior, severity, and impact.

More than One Kind of Flu?

While both types cause seasonal flu and share many similarities, there are important distinctions in their behavior, severity, and impact.

Differentiating between influenza types helps healthcare providers tailor treatment strategies, monitor outbreak patterns, and develop effective vaccines. It also aids in understanding the potential severity and risks associated with each type, which is critical for public health planning and response.

Similarities Between Influenza A and B

Influenza A and B are both highly contagious viruses responsible for seasonal flu outbreaks. They spread through respiratory droplets when an infected person coughs, sneezes, or talks. Both types cause similar flu symptoms, including fever, cough, sore throat, body aches, fatigue, and chills. Additionally, both can lead to complications such as pneumonia, bronchitis, sinus infections, and worsening of chronic medical conditions, especially in vulnerable populations like young children, the elderly, and individuals with weakened immune systems.

Key Differences Between Influenza A and B

1. Timing of Symptoms and Outbreak Patterns

Influenza A often emerges earlier in the flu season, typically peaking from December to February. Influenza B, however, tends to appear later, with activity sometimes extending into the spring. This difference in timing can influence the overall length of flu season each year.

2. Symptom Type and Severity

While symptoms of both types are generally similar, influenza A is often associated with more severe illness. This is partly because influenza A viruses can infect both humans and animals, leading to more frequent mutations and the potential for new, more virulent strains. Influenza B primarily affects humans and tends to cause milder, though still significant, symptoms.

3. Duration of Influenza A and Influenza Illness

The duration of illness for both types typically ranges from 5 to 7 days, though symptoms like fatigue and cough can linger longer. However, influenza A may result in more prolonged and intense symptoms in severe cases, especially in individuals with compromised immune systems.

4. Risk of Long-Term Health Effects

Both influenza A and B can lead to serious complications, but influenza A carries a higher risk of severe outcomes due to its potential to cause pandemics and widespread outbreaks. Influenza A's ability to undergo antigenic shifts and drifts makes it more unpredictable and capable of causing long-term health issues in some individuals. Influenza B, while less likely to cause pandemics, can still result in severe illness, particularly in children.

Why It Matters

Understanding these differences is crucial for prevention and treatment. Annual flu vaccination remains the most effective way to protect against both influenza A and B. Practicing good hygiene, such as regular handwashing and covering coughs and sneezes, helps prevent the spread of both types.

By recognizing the unique characteristics of influenza A and B, individuals can make informed decisions about their health during flu season, seek prompt medical attention when needed, and contribute to reducing the spread of the virus in their communities.

Helpful Resources:

Centers for Disease Control and Prevention (CDC) - Types of Influenza Viruses

World Health Organization (WHO) - Influenza