Swine flu symptoms similar to those of human flu

Swine flu has similar symptoms to the more common, human seasonal form of influenza.

It is one of a number of viruses that cause illness among people and animals, causing respiratory problems, fever and fatigue.

Avian flu - which has previously been the subject of pandemic fears after humans began contracting it - is another deadly strain.

According to the Health Protection Agency, outbreaks of swine flu - a disease caused by type A influenza - regularly affect pigs.

People who are around pigs are most likely to suffer from the H1N1 virus but it is also possible for the virus to spread from person to person.

Evoking memories of the fears associated with bird flu, the latest perceived threat of a pandemic was brought to public attention after cases of human swine flu were reported in Mexico and parts of California and Texas in the US.

There have been no cases identified in the UK for at least 10 years.

Scientists found this virus is contagious and spreading from human to human although they do not know how easily the virus spreads between people, the HPA said.

The symptoms of swine influenza in people are similar to the symptoms of regular human seasonal flu and include fever, fatigue, lack of appetite, coughing and sore throat. Some people have also reported vomiting and diarrhoea.

Testing has shown that the human swine influenza H1N1 can be treated with the antivirals oseltamavir (Tamiflu) and zanamivir (Relenza).

Seasonal flu is caused by viruses that are adapted to spread in humans, who have some natural immunity to common strains and can boost it by immunisation with a vaccine.

Avian flu is caused by influenza viruses adapted for infection in birds while swine flu is caused by influenza viruses adapted for infection in pigs.

Potentially major problems can arise when human and animal flu viruses mix and lead to the development of new viruses which are resistant to immunity and can spread through the population, sparking a pandemic.

The HPA said it was too early to say whether the cases in Mexico and the US would lead to a larger outbreak or could represent the appearance of a potential pandemic strain of influenza virus.

There is currently insufficient evidence to understand the extent to which the cases are firmly linked.

Experts from around the world are working in close collaboration with the World Health Organisation to help determine what risk this situation poses to global public health.