Flu Influenza Types

When someone says that he or she has the flu, you envision the person lying in bed with fever, aches, cough, sneezing, and sniffling. All one needs to do is pop a few pills and hope to get better soon, right? It may seem that simple, but not all flu viruses are created equal! There are several types of influenza that you should learn to recognize. Some types of flu can cause severe health problems and even become fatal in extreme circumstances.

The Impact of Influenza in the United States

According to the World Health Organization, each year, influenza results in about 114,000 hospitalizations and over 35,000 deaths in the US alone. The influenza virus can spread rapidly and have potentially severe consequences, especially in people who have weak immune systems. Vaccinations, or “flu shots,” remain an important method of controlling outbreaks. Without them, the virus can spread like wildfire. Most commonly, viruses spread by respiratory air droplets. That’s why it’s important to cover your sneeze or cough.

There is more than one type of influenza. Predicting the types that will spread in a given flu season allows researchers to create vaccinations against those particular strains.

What are the Different Types of Influenza?

Experts recognize three different flu viruses that affect humans: type A, B, and C. Type A and B cause the yearly flu epidemics. Type C infects fewer people with milder symptoms. Type A and B are further broken down into subtypes, also known as “strains.” About 20 percent of the population will be affected each year by a certain group of flu strains. This year, there is a huge concern worldwide about the “swine flu,” or the influenza type A H1N1 virus.

Influenza Type A

Strains of influenza type A generally have their origins in wild birds. In humans, influenza type A causes moderate to severe symptoms. Influenza Type A constantly shifts its genetic makeup, meaning that it can infect and spread among people who are thought to be immune. Thus, the virus is able to “sneak past” our immune system defenses, causing recurrent flu symptoms.

The “swine flu,” or H1N1 virus, belongs to the influenza type A category.

Influenza Type B

Influenza type B is only found in humans and seals. For the most part, influenza type B only causes mild to moderate symptoms, but may still be very problematic in immunocompromised individuals (such as those with AIDs). Influenza type B viruses are not responsible for pandemics.

In addition, influenza type B can appear at any time during the year, while influenza Type A usually peaks around the winter and early spring months.

Types of Influenza - Influenza Virus Changes

Do I have the Flu?

Many people confuse the common cold with the flu. In general, one will be affected by the flu once every few years, and symptoms are more severe than those of the common cold.

Common flu symptoms include:

  • Body aches
  • Chest discomfort
  • Extreme fatigue
  • High fevers
  • Headaches.

The influenza A H1N1 (“swine flu”) should be considered when you have these flu symptoms. Your doctor can help diagnose your illness and take appropriate measures.


WebMD staff. (2009). Learn about the types of flu. Retrieved November 27, 2009, from the WebMD Web site: http://www.webmd.com/cold-and-flu/flu-guide/advanced-reading-types-of-flu-viruses?page=2.

Medline Plus staff. (2010). Flu. Retrieved November 27, 2009, from the Medline Plus Web site: http://www.nlm.nih.gov/medlineplus/ency/article/000080.htm.

World Health Organization. (2003). Influenza. Retrieved November 27, 2009, from the World Health Organization Web site: http://www.who.int/mediacentre/factsheets/2003/fs211/en/.