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You might know you have flu, but do you know which type you are dealing with? As if flu season wasn't stressful enough, it turns out there are actually three different types of flu that affect humans: influenza A, B, and C. While we generally use "the flu" as a catch-all term for all three viruses, each one affects us differently, and some types of flu are more severe than others.
According to the Centers for Disease Control and Prevention (CDC), the flu is primarily spread through respiratory droplets (created from sneezing, speaking, or coughing). If you come into contact with a surface or object that has any of the flu viruses on it, then touch your mouth, nose, or eyes, you are at risking of contracting the flu. Infectious disease expert Amesh A. Adalja, MD, notes that there are also countless different types of influenza A viruses that circulate in water fowl (the recent "bird flu" is the result of avian influenza A viruses). The flu can infect people within a six-foot radius and "live" for up to 48 hours depending on the surface — a fact that has us washing our hands frequently during flu season.
To give you a better idea of what to expect from each kind of influenza, we asked experts to break down the different types of flu. Read on to learn more about the various signs, symptoms, and treatments of each, plus how to tell them apart.
Experts Featured in This Article:
Amesh A. Adalja, MD, is an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security.
Raelene Brooks, PhD, RN, is a registered nurse and dean of the college of nursing at the University of Phoenix.
Different Types of Flu
The three main types of flu in humans include influenza A, B, and C. There's also influenza D, but this primarily affects cattle and is not known to infect people. Although each type of flu may affect your body differently, they can all have a serious impact, says nurse Raelene Brooks, PhD, RN.
"[A flu] is usually viral, and often involves both the upper airways (nose and throat) and lower airways (bronchus which is the passage leading to the lungs, and the actual lung tissue)" Dr. Brooks says. "Anytime the lower airway is affected, there is a concern surrounding the entire body's oxygenation and circulation."
Here's what sets each virus apart from one another:
- Influenza A: This type of flu is responsible for larger epidemics, and according to the CDC, it's the only category known to cause flu pandemics. Influenza A viruses can be broken down into further subtypes determined by the two proteins found on the surface of the virus: hemagglutinin (H) and neuraminidase (N). You might be familiar with H1N1 (aka "swine flu") which caused a pandemic in 2009. Influenza A can infect both animals and humans, and as previously mentioned, avian influenza (aka "bird flu") also falls into this category.
- Influenza B: Influenza B viruses are responsible for many of the seasonal flu epidemics. Still, influenza B is often milder than influenza A, can only infect humans, and does not usually cause pandemics.
- Influenza C: Of the three viruses that affect humans, influenza Type C is the most mild type of flu. According to the CDC, influenza C generally causes mild respiratory illness, can only infect humans, and does not lead to epidemics.
How to Tell Different Types of Flu Apart
There are a few ways to narrow down the type of flu you're dealing with. This can be especially useful if you have a weakened immune system, chronic illness, or are actively experiencing another medical condition. "Viral sub-typing is performed using diagnostic tests," Dr. Adalja says. This might include a rapid influenza diagnostic test (RIDT) which involves a nasal swab (although these typically don't differentiate between subtypes of Influenza A, per the CDC). Molecular flu tests are another option, including polymerase chain reaction (PCR) tests. These are generally more accurate and can detect smaller amounts of the flu, according to the Cleveland Clinic.
Different Types of Flu Symptoms
Generally speaking, symptoms of the flu include body aches, fever, and chills, Dr. Brooks says. However, if you want to know the specific virus you're dealing with, she says influenza A and B are usually similar in symptom presentation. These may include:
- Aching
- Cough
- Fever
- Congestion
- Runny Nose
- Sore Throat
Dr. Brooks says influenza C generally causes milder symptoms or sometimes no symptoms at all. Common flu C symptoms may include:
- Dry Cough
- Headache
- Muscle Pain
- Runny Nose
Which Type of Flu Is Most Severe?
Influenza A is generally considered the most severe. "Certain avian influenza viruses (H5N1, H7N9) have high case fatality rates (50 to 60 percent) but are constrained in the ability to spread between humans," Dr. Adalja says. "The 1918 H1N1 influenza virus, which was of avian origin, killed just one to two percent of those it infected, yet because of its transmission efficiency, may have killed 100 million people."
That said, influenza B is not to be underestimated. "Both can be severe, with influenza A and B reported to have similar rates of hospital stays, intensive care unit admissions, and deaths," Dr. Brooks says. "Another study reports that Influenza B was more likely to cause death in hospitalized children aged 16 or younger."
How to Treat the Different Types of Flu
For starters, it pays to know that the flu vaccine is designed to help prevent influenza A and B epidemics, Dr. Brooks says. Beyond getting your flu shot, "The body needs adequate hydration and nutrition to support the cells that are fighting on the front lines against bacteria and viruses," she says. Here's what she recommends for flu treatment and prevention:
- Get as much sleep as possible: Listen to your body and give it the rest it needs to fight the virus.
- Drink more water: Dr. Brooks recommends 10 to 12 glasses of water a day. "When more fluids are consumed, this adds to the body's overall blood volume and circulation," she says. "This increase in volume and blood flow carries more oxygen and nutrients to support our front-line immunity cells to fight the good fight against the virus/bacteria."
- Get some vitamin C: "Taking extra Vitamin C, zinc, and micronutrients found in any over the counter multivitamin will help to decrease inflammation," Dr. Brooks says. "Vitamin C is an antioxidant that helps neutralize free radicals in the body, so making sure you're getting enough Vitamin C will help support a healthy immune system." As always, make sure to check with a healthcare professional before trying any new supplements or medications.
- Maintain a healthy diet: What you eat when you're sick can make a big difference. Dr. Brooks specifically recommends foods rich in vitamins and protein. "Stick to whole foods such as fruits, vegetables, chicken, fish, potatoes, rice, and beans," she says. "These foods contain the macro and micro nutrients the body needs to support the front-line immunity fighter cells." Try to avoid foods high in sugar, fat, and preservatives — all of which can increase the body's inflammatory response, Dr. Brooks says.
- Have a cup of tea: "Ginger tea (boil raw ginger) and honey is another great anti-inflammatory remedy used in eastern medicine," Dr. Brooks says.
- Try vapor rub: If you're suffering from a bad cough and congestion, vapor rub can provide some temporary relief. "Vapor rub is a great over the counter remedy to open the nasal and throat passages," Dr. Brooks says.
- Gargle salt water: It might not sound appealing in the moment, but gargling with salt and warm water can help decrease inflammation of the throat lining, Dr. Books says.
— Additional reporting by Tamara Pridgett
Chandler Plante (she/her) is an assistant health and fitness editor for PS. She has over four years of professional journalism experience, previously working as an editorial assistant for People magazine and contributing to Ladygunn, Millie, and Bustle Digital Group.
Tamara Pridgett was an associate editor with PS Fitness. She's a NASM-certified personal trainer and Precision Nutrition level 1 coach, and was a Division 1 All-American sprinter.
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