Definition & Overview

Also known as influenza, flu is a common infectious condition that is viral in nature. Flu is often mistaken for common colds due to similar symptoms. However, the virus that causes flu is different from that of colds, and flu tends to be more serious than the latter. In fact, the most serious cases can be life threatening.

Cause of Condition

Flu is caused by the influenza virus. People usually catch it through the following means:

  • by breathing in tiny virus-containing droplets from the sneeze or cough of someone who has the flu

  • by coming in direct contact with the secretions of an infected person, such as through touching, kissing, or sharing food utensils

  • touching a part of the body or an object (doorknobs, towels, handles, TV remotes, keyboard, telephone, etc.) that contains the virus. The virus can be transferred or absorbed by one touch of the eyes, nose, or mouth.

Flu viruses are classified as Types A, B and C, with Type A classified further into sub-types depending on the virus’ chemical structure (surface proteins). The Type of virus contracted would result in varying symptoms, details of which will be explained shortly. Types A and B cause the most common types of viruses and are responsible for influenza epidemics and seasonal outbreaks of flu. Type A viruses can occur in both animals and humans, while type B influenza occurs in humans alone.

Type C flu is not as common and is unrelated to seasonal flu. It usually causes mild respiratory symptoms and is less serious than other types.

Many people catch the flu more often than others. Moreover, flu outbreaks usually occur in winter months due to ideal conditions for the virus to survive and when people are mostly indoors and in more constant contact with others.

Key Symptoms

Flu symptoms start from one to seven days after coming in contact with the flu virus. The virus mostly affects the throat, nose and lungs. The symptoms often start quickly, and typically start with a fever between 38.8 to 40 ºC (102 - 106 ºF). Along with the fever, common symptoms include the following:

After a few days, the body pains and fever usually subside. However, new symptoms start to occur which may include:

  • Dry or phlegmy cough
  • Runny nose (clear and watery)
  • Sneezing
  • Nasal congestion
  • Heavy breathing

It usually takes about 7 days for all symptoms to completely go away. For some people, the cough and the feeling of tiredness may persist for weeks. For others, breathing problems like asthma and other long-term illnesses are made worse by flu.

It is important to note the difference between flu and cold symptoms. A common cold is also viral in nature, but is generally milder in symptoms and goes away after a few days. Flu, however, makes you unwell and exhausted for a long period of time. The flu can also complicate into serious health problems like pneumonia and may sometimes require hospitalization.

A flu patient is contagious from a day before to up to seven days after the first symptoms were observed, even after most symptoms have subsided. Young children with the flu can be contagious even after the second week of the illness.

Who to See & Types of Treatments Available

If you are completely healthy and fit, and you are experiencing flu-like symptoms or suspect that you have the flu, there is usually no need to see a doctor. Most healthy people can recover from influenza without any complications. It is best to stay in to rest, keep warm and hydrated. Over-the-counter medications such as paracetamol or ibuprofen can work well in lowering high temperature, relieve body aches and control other symptoms.

However, higher risk patients and very young children experiencing flu symptoms should visit their general practitioner as soon as possible for proper guidance and medical advice. This is because the flu virus can have more serious effects on you and your doctor can prescribe an appropriate anti-viral medication. You are considered high-risk if you:

  • have a long-term medical condition such as heart, kidney, lung or neurological disease or diabetes
  • are aged 65 or over
  • are pregnant
  • have compromised immune system due to genetic factors

Anti-viral medications can prevent serious flu symptoms and shorten its duration, but only if taken promptly as soon as the symptoms start. Anti-bacterial medications, on the other hand, are not recommended for flu as it is not bacterial in nature.

Seeking medical attention immediately is a must if you are experiencing atypical flu symptoms including:

  • Difficulty in breathing
  • Blue or purple discoloration of the lips
  • Sudden, uncontrollable dizziness
  • Confusion in everyday things
  • Unconsciousness
  • Appearance of rashes
  • Severe vomiting
  • Body temperature of more than 40 ºC (105 ºF)
  • Seizures
  • Pain in the abdomen or chest

Some of the complications that may be caused by influenza include: ear or sinus infections, dehydration, pneumonia, and worsening of existing chronic medical conditions.

Preventing flu

Since influenza is viral in nature, one can prevent it by strengthening the immune system with a balanced diet, adequate exercise, and enough rest or sleep. Proper hygienic practices such as regular hand washing and regular cleaning of surfaces you regularly touch can help prevent contracting the virus. It also helps to avoid unnecessary contact with people with flu.

Moreover, flu vaccine is available today in the form of injection or nasal spray in children. Flu vaccine is advisable for all and is strongly suggested for those who are at a higher risk for complications (as described above). Flu vaccine can work against Types A and B flu virus.


  • Asthma and Allergy Foundation of America: "Flu (Influenza).
  • National Institute of Allergy and Infectious Diseases: "Flu (Influenza): Causes."
  • Influenza (Flu) Viruses. (2011) Centers for Disease Control and Prevention.
  • About the Flu. (n.d.)
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