What is Flu?

Updated at: Feb 28, 2013
What is Flu?

Flu is a common viral infection, which affects the throat, nose and lungs. Flu is caused because of infection with any of the three types of influenza virus namely, type A, B, or C. Severity of symptoms in flu may vary from mild to severe. Treatme

Dr Poonam Sachdev
Communicable DiseasesWritten by: Dr Poonam SachdevPublished at: Feb 28, 2013

What is FluIn a closed community, such as school or workplace, most people develop symptoms within 2 or 3 weeks of the flu's arrival in the place. A person with flu is infectious i.e. he/she can transmit the infection to others a day before the symptoms start and for about five or six days after the start of symptoms.


Flu is caused because of infection with any of the three types of influenza virus  namely, type A, B, or C. It spreads by droplets formed when you cough or sneeze (influenza virus is present in small droplets formed when a person coughs or sneezes).

Many people think that flu and common cold are similar, however, in fact, both are different illnesses even though they have many similar symptoms. Common cold is also a viral infection, but it can be caused by several different types of viruses (>200 types), such as rhinovirus, coronavirus, adenovirus, respiratory syncytial virus and parainfluenza virus. The symptoms of flu tend to be more severe and last longer. You may get flu at any time of the year, but it is especially common in winter. The virus may spread by contact as well.

Severity of symptoms in flu may vary from mild to severe. In occasional cases, it may cause death, however, in most cases, it is a self limited disease in which the symptoms improve in a few days without complications.

Some factors that increase the risk of complications in flu are:

  • age more than 65 years
  • pregnancy (especially after the first three months)
  • chronic diseases, such as chronic heart disease; asthma or any other chronic lung disease;  kidney disease (such as renal failure, end stage renal disease); chronic liver disease (such as cirrhosis, chronic hepatitis); diabetes, which increases the risk of complications and death in flu
  • any serious medical problem (such as cancer; weak immune system because of  disease, medication or treatment)
  • living in a long-term care facility

Symptoms of flu

Symptoms typically start abruptly 1 - 7 days (usually within 2 - 3 days) after getting infected.

Some common symptoms of flu include:

  • fever. This is usually the first symptom and is high grade (between 102 and 106 °F). Adults usually do not have fever as high as a child.
  • body pain and aching muscles (myalgia)
  • feeling tired or without energy
  • headache
  • cold or runny nose
  • sore throat
  • cough
  • decrease in appetite
  • stomach upset, such as diarrhoea or vomiting (more common in children).

In most people, the symptoms peak after two to three days (of start of symptoms). Most people recover in a week or so, but you may feel tired for much longer.


Treatment of flu includes symptomatic treatment, such as rest, taking plenty of fluids, fever reducing medicine, such as acetaminophen and tepid sponging to reduce high fever. Antiviral drugs are not prescribed for every one with flu-like symptoms. These are recommended for people, who have severe infection or who are likely to develop complications.




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