What is a Influenza? | Types, Definition, Structure, Function & Facts

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What is (Disease) Influenza?

Influenza is the long name for the illness we commonly refer to as “the flu”. It occurs when the body is infected with one of many influenza viruses. The virus usually attacks the respiratory system, including the lungs, throat, and nose.

Typical Symptoms

Because there are many different types of flu, the symptoms are not always the same. Also, different people will have different symptoms. However, most people with the flu have some common symptoms, including:

  • Fever over 100 degrees F
  • Cough
  • Have a runny nose
  • Body aches and soreness
  • Headache
  • Tiredness and weakness
  • Chills and sweating

Some of the rarer symptoms include rash, diarrhea, and stomach pain. It usually takes about a day after infection for symptoms to begin.

How do you get the flu?

Influenza viruses are transmitted from person to person. It can move through the air when someone sneezes or coughs. It can also be transmitted when someone touches an object that an infected person has just touched.

We usually get the flu when the virus spreads on our hands and then we touch our mouth, nose or eyes. It can happen to us when we shake hands with a sick person or touch something like glass, a doorknob, or a phone that an infected person has held. That’s why it’s so important to wash your hands if you don’t want to get sick.

Is influenza Dangerous?

In general, the flu is not dangerous. Most people get better in about a week. However, sometimes people can become sicker from the flu, and this can lead to other complications like pneumonia and ear infections. People over 65, young children, and pregnant women are at higher risk of complications. Thousands of people die each year from flu-related complications. Most of them are elderly people with pneumonia.

Influenza viruses in the past were much more deadly. In 1918, a global flu pandemic known as the Spanish flu killed more than 50 million people.

Types of Influenza

There are several different strains and types of influenza virus. The three main types are called A, B, and C. Type “A” is generally the deadliest with the most severe symptoms in humans. Each year a new breed is born, different from the previous year. That’s why you should get a flu shot every year.

Sometimes different strains of flu are named with letters and numbers. Influenza A viruses with an H and an N in their name refer to the scientific terms Hemagglutinin and Neuraminidase. Some examples of this include H1N1 (which caused the 1918 Spanish flu and 2009 swine flu) and H5N1 (commonly known as avian flu).


There are not many treatments for the flu once a person is infected. Most of the time, doctors recommend bed rest and plenty of fluids. People at risk of complications should see a doctor and possibly go to the hospital.

Can you help prevent Influenza?

Several measures can be taken to avoid getting the flu virus:

  • Vaccine against Flu
  • Wash your hands often
  • Cover your mouth and nose with a tissue or with your elbow when sneezing or coughing
  • Avoid shaking hands with others
  • Avoid crowds during flu season

Interesting Facts about Influenza

Not everyone infected with the flu virus has symptoms. Some people (about 33%) are asymptomatic, meaning they carry the flu virus but have no symptoms.

People are usually contagious one day before they get sick, and then five to seven days after.

More people died from the Spanish flu than all the wars of the 20th century combined.

Flu outbreaks tend to be seasonal. Winter is often referred to as “flu season”.