Influenza virus

What is Influenza (also called Flu)?

The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.

Signs and Symptoms

People who have the flu often feel some or all of these signs and symptoms:

  • Fever* or feeling feverish/chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue (very tired)
  • Some people may have vomiting and diarrhea, though this is more
  • common in children than adults.

*It’s important to note that not everyone with flu will have a fever.

How Flu Spreads

Most experts believe that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can end up in the mouths or noses of people who are nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes or possibly their nose.

Period of Contagiousness

You may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer period. The time from when a person is exposed to flu virus to when symptoms begin is about 1 to 4 days, with an average of about 2 days.

Complications of Flu

Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

People at High Risk from Flu

Anyone can get the flu (even healthy people), and serious problems related to the flu can happen at any age, but some people are at high risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant women, and young children.

Preventing Flu

The first and most important step in preventing flu is to get a flu vaccination each year. The CDC also recommends everyday preventative actions (like staying away from people who are sick, covering your mouth when you cough and sneeze and frequent handwashing) to help slow the spread of germs that cause respiratory illnesses (i.e. of the nose, throat, and lungs), like flu.


There are influenza antiviral drugs that can be used to treat flu illness.

Oseltamivir, zanamivir and peramivir

More References:

  1. John, Pramod R. John (2008). Textbook of Oral Medicine. Jaypee Brothers Publishers. p. 336. ISBN9788180615627.. CDC. 6 October 2015. Retrieved 4 February 2016.
  2. Eccles R (November 2005). “Understanding the symptoms of the common cold and influenza”. Lancet Infect Dis. 5(11): 718–25.
  3. Bennett, John E.; Dolin, Raphael; Blaser, Martin J. (2014). Principles and Practice of Infectious Diseases. Elsevier Health Sciences. p. 750. ISBN9781455748013.
  4. Allan, GM; Arroll, B (18 February 2014). “Prevention and treatment of the common cold: making sense of the evidence.”. CMAJ : Canadian Medical Association.
  5. Heikkinen T, Järvinen A (January 2003). “The common cold”. Lancet. 361(9351): 51–9.  Arroll, B (March 2011). “Common cold”. Clinical evidence. 2011 (3): 1510.  3275147 .  21406124. Common colds are defined as upper respiratory tract infections that affect the predominantly nasal part of the respiratory mucosa
  6. Kim, SY; Chang, YJ; Cho, HM; Hwang, YW; Moon, YS (21 September 2015). “Non-steroidal anti-inflammatory drugs for the common cold.”. The Cochrane database of systematic reviews. 9: CD006362.
  7. Simasek M, Blandino DA (2007). “Treatment of the common cold”. American Family Physician. 75(4): 515–
  8. Pelczar (2010). Microbiology: Application Based Approach. p. 656.
  9. medicine, s cecil. Goldman(24th ed.). Philadelphia: Elsevier Saunders. p. 2103. .
  10. Michael Rajnik; Robert W Tolan (13 Sep 2013). “Rhinovirus Infection”. Medscape Reference. Retrieved 19 March 2013.
  11. National Institute of Allergy and Infectious Diseases. 27 November 2006. Archived from the originalon 6 September 2008. Retrieved 11 June 2007.}}
  12. Eccles, Ronald; Weber, Olaf (2009). Common cold