"In the medium term, nobody really knows because it’s in an early stage of the outbreak. It may be that it will disappear because we are at the end of the influenza season. But we just have to keep watching it.

"If it spreads and spreads then everyone needs to be far more worried."

Swine influenza is a respiratory disease normally found in pigs. It is suspected to have killed more than 100 people in Mexico, with cases also reported in the USA, Canada and Spain.

Antiviral drugs can effectively prevent and treat the infection, and most reported cases outside of Mexico have recovered fully without the need for medical attention.

But the UN has warned that the virus has the potential to become a pandemic.

Liverpool’s executive member for health, care and safeguarding Cllr Ron Gould, a professional pharmacist, said: "There will undoubtedly be concerns about swine flu.

"A lot of people go to Mexico on holiday from this area, but if they're not showing any symptoms that's fine, but we’ve got drugs including Relenza and Tamiflu.

"One works on the effects of the disease and the other tries to stop it spreading. But it seems the problem with this particular flu is it affects healthy people in the age range 15 to 45 and attacks the immune system."

"People should ring their doctor first or contact NHS Direct, but if they really feel ill they should go to A and E.Spokesperson for the HPA in Merseyside, Hugh Lamont, added: "People visiting these countries should be aware of the symptoms and if they experience them they should seek medical help.

"People coming back should monitor their health and call their GP or NHS Direct for a phone consultation if they start to develop flu symptoms."