William Lodge / Alamy
“Swine flu” is the common name for a disease that emerged in January 2009, causing a pandemic that lasted until the middle of the following year. It is caused by a novel strain of the influenza virus called H1N1, which seems to have .
What set swine flu apart from other strains of seasonal flu is that children and younger adults were most likely to be infected. The explanation for this is that many older people had previously been exposed to a variant of the H1N1 virus, which, although substantially different, gave them some immunity to swine flu. The virus is estimated to have in the first year it circulated.
As H1N1 spread from its epicentre in Mexico, it evolved to become less deadly. It continues to circulate and is now a regular seasonal flu virus. Many people now have immunity to it and a . If you do contract it, the symptoms are likely to be the same as other types of flu. However, swine flu does still just as seasonal flu does.
