Monday, 05 May 2014 09:53



Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs and result in nasal secretions, a barking cough, decreased appetite, and listless behaviour. Approximately 1% to 4% of pigs that get swine flu die from it. It is spread among pigs by direct and indirect contact, aerosols, and from pigs that are infected but do not have symptoms. In many parts of the world pigs are vaccinated against swine flu.

Influenza A viruses in swine are categorized into subtypes based on two viral surface antigens called hemagglutinin (H) and neuraminidase (N). Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine flu viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge.

Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2 and H3N1. However, most of the recently isolated influenza viruses from pigs have been H3N2 and H1N1 viruses. The current outbreak of swine flu that has infected humans is of the H1N1 type.


The virus spreads by tiny droplets that are released when a person coughs or sneezes. The droplets reach a distance of about one metre (3ft). These droplets remain suspended in the air for a short duration, and then settle on a surface. The virus suspended in airborne droplets can infect a person, if the person inhales the contaminated droplet.

Common objects such as door handles, remote control, hand rails and computer keyboards can get contaminated with the virus when the droplet settles on these surfaces. If a person touches these surfaces and places the contaminated hands on their mouth or nose he or she can get the infection. They can spread it further by touching other things. If the droplets land on a hard surface the virus can survive for about 24 hours, and on a soft surface it survives for about 20 minutes.


Symptoms of swine flu are similar to most influenza infections: fever (100 0F or greater), cough, nasal secretions, fatigue, and headache, with fatigue being reported in most infected individuals. Some patients also get nausea, vomiting, and diarrhea.

Some patients develop severe respiratory symptoms and need respiratory support (such as a ventilator to breathe for the patient). Patients can get pneumonia (bacterial secondary infection) if the viral infection persists, and some can develop seizures. Death often occurs from secondary bacterial infection of the lungs; appropriate antibiotics need to be used in these patients.

High-risk groups

Some people are more at risk of complications if they catch flu. People are particularly vulnerable if they have:

• chronic (long-term) lung disease

• chronic heart disease

• chronic kidney disease

• chronic liver disease

• chronic neurological disease (neurological disorders include motor neurone disease, multiple sclerosis and Parkinson's disease)

• immunosuppression (whether caused by disease or treatment)

• diabetes mellitus

Also at risk are:

• patients who have had drug treatment for asthma in the past three years

• pregnant women

• people who are 65 years of age or over

Treatment H1N1 swine flu virus is sensitive to the antiviral drugs Tamiflu and Relenza. These antiviral drugs are most effective when taken within 48 hours of the start of flu symptoms. It's resistant to older flu drugs.

A third antiviral drug, peramivir, can be used only in hospitalized patients with severe flu.




Last Updated on Monday, 05 May 2014 10:01

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