Knowing which flu is worse, A or B, can be helpful as we head into flu season.
Influenza, or the flu, is a highly contagious respiratory illness that spreads from person to person and comes in two main types that affect humans: flu A and flu B. Both types produce similar symptoms, but they can differ slightly in symptom severity, symptom onset and how their symptoms impact various individuals.
These variations can be crucial, particularly in diagnosing and managing flu cases during peak seasons. Case numbers for flu viruses typically peak between December and March of each year in the United States, although flu season can start earlier and continue into late spring.
Let’s quickly review the common symptoms of both types of flu virus.
According to the Centers for Disease Control and Prevention (CDC), the following are the shared symptoms of flu A and B:
- Fever and chills
- Coughing and sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches
- Fatigue
These symptoms often overlap with other types of respiratory illness, which can make distinguishing if you have the flu challenging. But once you’ve been diagnosed with the flu by your health care provider, slight variations in symptom onset and intensity can sometimes give clues to which influenza type you might have.
Symptom severity, duration and risk groups
Flu A
Known to be more intense in symptom severity, influenza A often causes stronger fevers and body aches, making people feel significantly worse than they might with influenza B. The symptoms of flu A also tend to escalate quickly, sometimes within hours of infection.
Flu A tends to produce more severe upper respiratory symptoms as well, such as a dry cough and sore throat. Patients with influenza A may notice that their cough is more intense and persistent, which can last even after other flu symptoms subside. As for gastrointestinal symptoms, they are rarer in flu A but can occur, especially in young children and people with weakened immune systems. When GI symptoms, like vomiting and diarrhea, arise with flu A, they tend to be mild.
Older adults, pregnant people and immunocompromised individuals often experience more severe symptoms from influenza A. Complications, including pneumonia and bronchitis, are more common in flu A cases, making it more challenging for these individuals to recover fully. However, flu B can also cause severe symptoms in this group and should not be underestimated.
Flu B
Symptoms of flu B tend to be milder overall compared to flu A, although this can vary from person to person. Body aches, fever and other symptoms can be less intense, and the fever may break sooner. However, this isn’t always the case, as flu B can also cause severe symptoms, particularly in young children. Symptoms associated with influenza B may also develop at a slightly slower pace than with flu A.
As for nasal congestion and a runny nose, they are more frequently reported with influenza B than with flu A, though both types can cause these symptoms. Children with flu B, in particular, might experience more pronounced nasal congestion, which can sometimes lead to sinus infections.
Influenza B is more commonly associated with gastrointestinal issues and can cause nausea, vomiting and occasionally diarrhea, especially in children. This difference means that parents might be more likely to see GI symptoms in their children if they have flu B rather than flu A.
Both flu A and B can cause severe illness in children, but flu B is more frequently associated with higher rates of illness in young children and teens. Flu B symptoms in children may include higher rates of fever and more intense GI symptoms, making the illness appear distinct from the typical respiratory symptoms seen with flu in adults.
Which strain of flu is covered in the flu vaccine?
Both influenza A and B strains are included in the seasonal flu vaccine, which is updated annually based on predictions about the most common strains for that flu season. Flu vaccines remain the most effective preventative measure, which is why it is so important to get one every year!
“Parents should know that children should receive the influenza vaccine twice, greater than four weeks apart, during their very first influenza season, once they are 6 months or older,” Brady S. Christensen, DO, a family physician at Bon Secours Medical Associates, shares. “Now, patients with any history of egg allergy can receive an influenza vaccine. Be sure to speak with your primary care provider about which vaccine is best for you. Also, the influenza vaccine is safe and recommended during pregnancy!”
And for those that do end up getting sick this flu season, antiviral medications, such as oseltamivir (Tamiflu), are effective for both influenza A and B when taken early in the illness. These drugs can reduce symptoms, shorten the duration of the illness and decrease the risk of severe complications
“The best way to treat influenza A and B is by early diagnosis and treatment,” Dr. Christensen adds. “There are antiviral medications that can shorten the duration of symptoms and reduce the severity of influenza, but they need to be started within 48 hours of symptom onset.”
If antivirals aren’t an option for you, over-the-counter medicines, like acetaminophen and ibuprofen, can help you manage any discomfort with symptoms such as fever and body aches. Also, make sure you are drinking plenty of fluids and getting lots of rest.
For most individuals, symptoms from flu A or flu B should resolve within one to two weeks. However, in severe cases, both types can lead to complications such as pneumonia, bronchitis and sinus infections, especially in higher-risk groups.
So, which flu is worse, A or B? As you can see, it’s a complicated answer that depends on a lot of different factors! The most important thing you can do this flu season to help keep everyone safe is to practice prevention methods such as handwashing, getting your flu shot and staying home when you are under the weather.
Need to speak with a health care provider about your flu-like symptoms? Learn about the primary care services we provide at Bon Secours.
