Hans Classroom: 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. 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 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.

Although swine influenza tends to just infect pigs, they can, and sometimes do, jump the species barrier and infect humans.

People who are not in close contact with pigs generally have no immunity to the swine influenza viruses - they are less likely to be able to prevent a virus infection. If the virus infects enough people in a given area, the risk of an influenza pandemic is significantly greater. Experts say it is very hard to predict what impact a flu pandemic caused by a swine influenza virus would have on the global human population. This would depend on how virulent the virus is, what existing immunity among humans there already is, plus several other factors.

Do we have a specific swine flu vaccine? No - not for humans. Will current human flu vaccines help protect people from swine influenza infection? We really don't know. Influenza viruses are adapting and changing all the time. If a vaccine was made, it would have to be specifically for a current strain that is circulating for it to be effective.