It was only going to be a matter of time before an outbreak of the H5N1 strain of bird flu appeared in the UK.

With cases reported across Europe, including nearby France, and an isolated case of a swan in Scotland last year, scientists had braced themselves for the inevitable.

Professor Jon Cohen, a renowned expert in infectious diseases, says at this stage the only people at risk of becoming ill are those who work very closely with infected poultry.

He said: "You would need to work with them pretty intensely and over a prolonged period but even then the risk is slight.

"The concern among many people however is the theoretical risk the H5N1 strain will come into contact with a human form of flu and adapt so that it can be passed between humans.

"There is no case that has happened but it remains a very real possibility that this could take place and it is something that is being worked on all the time.

"Studies are continuing to work towards a vaccine and there have been some preliminary vaccines which are being developed to see if they are effective.

"Normally flu vaccines are developed through the use of chicken eggs but obviously in this case that can't be done."

Prof Cohen said there was also no need to stop eating chicken or turkey.

He said: "There are no cases of the disease being linked to consumption and as long as it is cooked properly, chickens and turkeys are safe to eat.

"The important thing is people should not panic. The incident at Suffolk appears to have been contained within the farm effectively and there is no evidence this is going to affect humans."

Despite the risk being low, Sussex has already put itself on standby with contingency plans drawn up by West Sussex County Council, East Sussex County Council and Brighton and Hove City Council.

West Sussex cabinet member for public protection, Lionel Barnard, said: "We have a well rehearsed action plan in place should the disease edge nearer."

If ten birds of any species are found dead in the same location, each council would contact the State Veterinary Service based at Reigate in Surrey.

Anyone finding ten dead birds should call DEFRA helpline on 08459 335577.

All authorities have stressed that the infection has not entered the food chain.

Almost 159,000 birds are being culled at the Bernard Matthews farm in a bid to contain the outbreak and the Health Protection Agency have offered workers anti-viral drugs.

They are also being monitored and seen by doctors.

The source of the infection is still a mystery and studies are under way to pinpoint how it might have happened.

Some experts believe the source is from a wild bird that has flown in.

Wardens are closely monitoring wild birds on reserves around Britain as experts try to trace the source.

RSPB officials said staff were maintaining regular patrols at the Minsmere reserve near Saxmundham, Suffolk - closest to the outbreak of bird flu at the Bernard Matthews farm but similar checks were being held at all 200 of its reserves. including Pulborough Brooks in West Sussex.

A spokesman said: "We have been monitoring wildlife at all our reserves very closely since the outbreak of bird flu early last year.

"That is still going on today. To be honest, I'm not sure how much more stringent we could be.

"So far we have seen nothing on any reserves to give us cause for concern."

Farmers are also bracing themselves against potential impact on sales of poultry.

Charles Bourns, chairman of the National Farmers Union poultry board, is urging shoppers to carry on buying chicken and eggs.

He said: "Just keep eating chicken and enjoying it. There is no danger from it. This is a disease of chickens and not of humans."

Health Secretary Patricia Hewitt said the risks of a pandemic were very remote but the Government was preparing very seriously and thoroughly just in case.

The Department of Health has stockpiled enough Tamiflu anti-virals to cover a quarter of the population, as advised by scientists and conducted a massive preparatory exercise last week.

Although 164 people have died from H5N1 since January 2003, mostly in Asia and the Middle East, the virus is not transmitted through food.

For more information on avian flu visit www.defra.gov.uk