What is Swine Flu?
Swine flu (swine influenza) is a disease of pigs. It is a highly contagious respiratory disease caused by one of many Influenza A viruses. 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.
Most commonly, swine flu is of the flu.mytipsonline.info”title=”" >H1N1 influenza subtype. However, they can sometimes come from the other types, such as H1N2, H3N1, and H3N2.
The current outbreak of swine flu that has infected humans is of the H1N1 type – this type is not as dangerous as some others.
Avian Influenza (Bird Flu) can also infect pigs
Avian flu and human seasonal flu viruses can infect pigs, as well as swine influenza. The H3N2 influenza virus subtype, a virulent one, is thought to have come from pigs – it went on to infect humans.
It is possible for pigs to be infected with more than one flu virus subtype simultaneously. When this happens the genes of the viruses have the opportunity to mingle. When different flu subtypes mix they can create a new virus which contains the genes from several sources – a reassortant virus.
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Although swine influenza tends to just infect pigs, they can, and sometimes do, jump the species barrier and infect humans.
What is the risk for human health?
Outbreaks of human infection from a virus which came from pigs (swine influenza) do happen and are sometimes reported. Symptoms will generally be similar to seasonal human influenzas – this can range from mild or no symptoms at all, to severe and possibly fatal pneumonia.
As swine flu symptoms are similar to typical human seasonal flu symptoms, and other upper respiratory tract infections, detection of swine flu in humans often does not happen, and when it does it is usually purely by chance through seasonal influenza surveillance. If symptoms are mild it is extremely unlikely that any connection to swine influenza is found – even if it is there. In other words, unless the doctors and experts are specifically looking for swine flu, it is rarely detected. Because of this, we really do not know what the true human infection rate is.
Examples of known swine flu infecting humans
Since the World Health Organization’s (WHO’s) implementation of IHR (2005) in 2007, they have been notified of swine influenza cases from the USA and Spain.
In March/April 2009 human cases of influenza A swine fever (H1N1) were first reported in California and Texas. Later other states also reported cases. A significant number of human cases during the same period have also been reported in Mexico – starting just in Mexico City, but now throughout various parts of the country. More cases are being reported in Canada, Europe, and New Zealand – mainly from people who have been in Mexico.
How does a human catch swine influenza?