animal / disease

Warnings as swine virus spreads Latest Q&A World ready? Reports map Economy alert In pictures

Infection control experts are scrambling to respond to outbreaks of swine flu in Mexico and the US, and suspected cases elsewhere. HOW SWINE FLU OUTBREAK EMERGED Flu viruses mutate over time causing small changes to proteins on their surface called antigens. If the immune system has met particular strain of the virus before it is likely to have some immunity; but if the antigens are new to the immune system, it will be weakened. The flu currently making headlines is a strain of H1N1 influenza A virus, which affects birds, some mammals and humans.