Influenza A vs. B: Which is worse?

What are Influenza A and B Causes, Symptoms and Prevention
Influenza A vs. B are common types of flu (Photo: Medical News Today)

It starts small. You might wake up with an annoying throat tickle and a runny nose, or you might feel a little more groggy throughout the day than usual. But there’s more on the way. You come down with a fever, chills, body aches, and you’re couch-ridden with the flu.

“The flu” has become a broad term that people use to incorrectly describe a wide range of illnesses. We often hear people say “oh, I came down with the stomach flu last week,” or “the kids got the 24-hour flu.” But “flu” refers to four types of influenza viruses (A, B, C, and D), most prominently influenza A and influenza B.

Influenza A can infect humans and animals. In most cases, it’s associated with seasonal epidemics in the United States (aka “flu season“) and global pandemics. It’s always changing, so it has various subtypes, including the infamous bird flu (avian influenza) and swine flu. On the other hand, influenza B has two subtypes (Victoria and Yamagata), which occur, for the most part, only in humans and mutate slower, so it’s not really a pandemic risk, cites singlecare.

Causes of Influenza A and B

Influenza A's Causes

The most common form of transmission is through tiny droplets created when an infected person talks, sneezes, coughs, or breathes heavily. Type A is also (albeit very rarely) contracted via contact with an infected animal, like a bird or pig. Influenza can also be transmitted through inanimate objects if a sick individual contaminates it, such as a doorknob.

Influenza B's Causes

Like influenza A viruses, influenza type B is primarily transmitted through contact with the droplets when an infected individual coughs, sneezes, or talks. Animals aren’t usually susceptible to the influenza B virus, so generally aren’t considered to be carriers.


Flu symptoms can range from mild to severe, and they vary from person to person, according to Medical News Today.

Common symptoms of the flu include:

  • fatigue
  • nasal congestion
  • a cough
  • headaches
  • a sore throat
  • body aches
  • chills
  • a fever
  • vomiting or diarrhea, which are more common in children

Some people experience severe symptoms, which can include:

  • chest pain
  • shortness of breath
  • severe pain
  • severe weakness
  • a high fever
  • seizures
  • severe dizziness
  • loss of consciousness

A person who experiences any severe symptom should receive medical attention.

Treatment Influenza A and B

What are Influenza A and B Causes, Symptoms and Prevention
Photo: Webmd

Many people find that home remedies can help ease flu symptoms, but prescription antiviral medication may be a good idea for people with a high risk of complications or severe symptoms.

Home remedies Influenza A and B

To reduce flu symptoms at home:

  • drink plenty of fluids
  • get plenty of rest
  • take over-the-counter medications such as ibuprofen or acetaminophen to relieve any pain

Antiviral medications

Antiviral medications are available by prescription only. They can shorten the duration of symptoms or prevent complications, such as pneumonia.

Antivirals can especially benefit people with a greater risk of flu complications, including young children, older adults, pregnant women, and people with certain chronic illnesses.

Antiviral medications work best when a person takes them within 1–2 days of symptoms starting.

There are a few different types of antivirals for the flu, including:

  • oseltamivir
  • zanamivir
  • peramivir
  • baloxavir marboxil

These can come in pill, liquid, inhalable powder, or intravenous forms.

Diagnosis Influenza A and B

Symptoms of the flu are largely similar to those of the common cold or a respiratory infection, so you may not be able to discern between the issues on your own. Luckily, your doctor can formally diagnose you with the flu with a test that confirms the presence of the influenza virus. However, while fast and non-invasive, a flu test may not always deliver accurate results.

In some cases, your doctor may diagnose you with the flu (or at least recommend you be treated for infection) based on your symptoms, whether or not someone else in your household has the flu, or if cases of influenza are increasing in your area.


The main difference between a cold or upper respiratory infection and influenza is how the illnesses come on. While the first two tend to start slowly and gradually worsen over a few days, the flu progresses rapidly, typically starting with a headache that quickly escalates to severe body aches and fatigue.

Common flu symptoms include:1

  • Fever
  • Fatigue/exhaustion
  • Cough
  • Body aches
  • Headache
  • Chills

If you believe you have the flu, try to see your healthcare provider within the first 48 hours of the onset of symptoms. If you do need a flu test, it is more likely to be accurate if it is performed within this time frame.2

Even if you are convinced that you have the flu, you cannot diagnose yourself. Get a medical opinion to ensure that your self-assessment is accurate and that you are not dealing with another condition that may require treatment.

Physical Examination

Your healthcare provider will ask you what symptoms you have and how long you have been sick to determine next steps. Your doctor will also look in your ears, nose, and throat and listen to your lungs with a stethoscope.

If flu activity is high in your area and your symptoms point to influenza, your doctor may diagnose and treat you simply based on these assessments and an elimination of other causes.

Labs and Tests

What are Influenza A and B Causes, Symptoms and Prevention
Photo: CBS News

There are many viruses that cause symptoms that are similar to those of the flu but will not respond to antiviral medications used to treat influenza.

Given this, your doctor may also perform an in-office flu test to determine if your symptoms are definitely due to the influenza virus. The flu test is especially useful when flu activity is low in your area but your doctor still thinks you might have it.

Rapid influenza tests can be run in the office and takes about 15 minutes to get results. The test typically involves a nasal or throat culture to determine whether influenza A or influenza B is present.

Although flu tests can be useful, some are undermined by the high rate of false-negative results. Some rapid tests, like the widely used BD Veritor System, have demonstrated a sensitivity (the ability to make a correct negative diagnosis) of only 78.8%.3

The rapid test is far more accurate in infants and becomes less and less accurate the older you get. In people over 70, the test sensitivity may be as low as 60%, all but erasing its benefits.2

Other more accurate tests can identify which strain of influenza is circulating in an area (such as influenza A/H1N1, a.k.a. the "swine flu"), although they are almost exclusively used for research purposes.

These tests take longer to run but can help public health officials assess the severity of a flu outbreak, determine the best treatment options, and plan for future influenza vaccines, shows verywellhealth.

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