What is swine flu?

Swine flu , now known as the 2009 H1N1 flu, is caused by the orthomyxovirus which usually affects pigs but viral mutations allows the virus to cross species to other hosts like humans. The swine influenza virus (SIV) is another example of cross species viral infection which was previously seen with other zoonotic infections like in civets to humans (SARS or Sudden Acute Respiratory Syndrome) and from birds to humans as seen with avian (bird) flu.

Unlike SARS and bird flu, swine flu has mutated to the point where the virus can now spread from human-to-human. This current mutation is the cause of the global scare of the recent 2009 outbreak which is feared to become a pandemic. With the popularity of air travel, infected passengers from one region can easily travel to other nations and result in new outbreaks occurring in regions that were not prone to swine flu. The current human-to-human transmission of swine flu is caused by droplet spread through the contact with infected body fluids as in saliva or mucus when sneezing.

2009-swineflu-h1n1

Scientific Name for Swine Flu

What was originally called, and is widely known as ‘swine flu’ since April 2009, when a new type of flu was discovered in a human in Mexico, is now named (according to World Health Organisation - WHO) as influenza A (H1N1) or, with a long term 2009 pandemic influenza A, subtype H1N1.

Other names for influenza A (H1N1):

  • ‘Novel flu’ or ‘new flu’ (in Europe)
  • ‘Pandemic flu’ or ’2009 pandemic flu’
  • ‘Pig flu’ (rarely)
  • ‘Mexican flu’

Symptoms of Swine Flu

Swine flu infection causes symptoms that are similar to the symptoms of influenza infection as seen during the annual ‘flu’ season. This may result in many cases of swine flu being misdiagnosed as a common cold or the ‘flu’ and if infected persons do not seek professional medical treatment, the infection can spread further in the general population.

The general symptoms of swine flu include :

  • Fever with or without chills.
  • Sore throat.
  • Respiratory symptoms, usually a cough or less frequently as dyspnea (difficulty breathing) or pneumonia.
  • Fatigue and lethargy
  • Myalgia (general body aches)
  • Vomiting

The current swine flu epidemic has seen gastrointestinal symptoms like diarrhea and vomitting that are more severe than previous swine flu outbreaks. Unfortunately these gastrointestinal symptoms may often be misdiagnosed as a ‘gastric flu’ and it is important to consult with your medical practitioner if your symptoms persist.

Treatment of Swine Flu

  • Oseltamivir (commonly marketed under the trade name Tamiflu) is being touted as the frontrunner in combatting this outbreak. Oseltamivir is an antiviral drug that is useful both as a treatment and as a preventative meausure against many influenza type viruses including swine flu, SARS and bird flu.
  • Zanamivir, another widely used antiviral has also been found to be effective in the treatment of swine flu. (CDC) Zanmivir is marketed under the trade name Relenza.

Prevention of Swine Flu

As with any disease, prevention is better than cure and a few conservative measures can greatly reduce your risk of swine flu infection. Proper hygiene and common sense are of the greatest benefit in dealing with any viral outbreak. A few simple tips to reduce your chances of swine flu infection include :

  1. Avoid close contact with any person suffering with the ‘flu’.
  2. Bed rest is advisable if or when you are feeling unwell. This will prevent further spread of the infection and allow your body the rest and relaxation required to recuperate.
  3. Always wash your hands after touching objects, other people and at regular intervals. A good antimicrobial soap is useful.
  4. If you are suffering with the ‘flu’, practice good hygiene to avoid infecting your loved ones. This includes blocking your mouth and nose when sneezing, throwing away used tissues and not sharing food, drink or personal items.

Diagnosis of Swine Flu

The symptoms of swine flu are non-specific meaning that it could be indicative of many other conditions including the common cold or the annual flu. However in the presence of these symptoms and a strong history of exposure to infected persons or other related factors, a differential diagnosis of swine flu should be considered.

A laboratory testing of mucus should be conducted to confirm the diagnosis. This is only relevant in the first few days of infection as swine flu is only contagious for 5 days.

How did the 2009 H1N1 flu develop?

Through close contact with humans, the swine influenza virus can be transmitted from pigs to humans. However the concern has revolved around human-to-human transmission of the swine influenza virus and it appears that the 2009 H1N1 flu virus has undergone a mutation which allows for the spread from human-to-human.

Human infection with swine flu has been noted previously in history notably in 1918, 1930 and 1976.  In these cases, the primary mode of zoonotic infection was from pig to human seen in farm workers who came in close contact with pigs.

The three main types of influeza viruses known to infect humans are influenzavirus A, B and C. Of these three types influenza virus A is common and endemic to pigs. This means that the influenza virus A commonly infects both humans and pigs.

The 2009 H1N1 flu is believed to be a result of a combination of bird strain of influenza virus A and the human strain of influenza virus A which may have infected pigs. As the virus reproduces within the pig host, there is a mix or reassortment of genes from both the bird and human strain of influenza type A. This results in a new strain of influenza virus A which is termed as the reassortment strain of influenza virus A.

This reassortment strain of influenza virus causes swine flu (pig-to-human) but can be transmitted from human-to-human and in the current outbreak, it is known as the 2009 H1N1 flu.


Article reviewed by Dr. Greg. Last updated on September 9, 2012