A Birmingham hospital is vaccinating its nurses and calling up reservists to be on standby as the region braces itself to cope with a potential swine flu outbreak.

Heartlands Hospital, the regional centre for infectious diseases, said action plans were underway to deal with any cases as one Walsall family were facing an anxious wait for swine flu test results.

The World Health Organisation said four in ten of the UK population could catch the deadly disease over the next six months if a pandemic breaks out.

The family of four from Walsall, who did not want to be identified, were tested for swine flu after returning from a two-week trip to Mexico.

They were tested at Walsall Manor Hospital after a daughter developed flu symptoms on Thursday. They were told to stay at home in isolation for two days. They are due to get the results back on Wednesday.

Two British cases have been confirmed so far, of Iain and Dawn Askham, of Polmont, near Falkirk, who had been on honeymoon in Mexico.

More swine flu tests being carried out on 23 people across Scotland and suspected infections have emerged across England and Wales with the Health Protection Agency awaiting test results.

Emergency medicine consultant Tony Bleetman, head of emergency planning at Birmingham’s Heartlands Hospital, said action plans were under way to ensure hospitals continued to run effectively.

The senior doctor added that the first victims of swine flu across the West Midlands would be referred to isolation wards at Heartlands, in Bordesley Green, as it is the regional centre for infectious diseases. Another is based in Stoke on Trent.

“It’s early days and we don’t know how serious this will be,” said Mr Bleetman. “Staff in the emergency departments and acute medical units are being provided with masks, gloves and aprons and vaccinated with the flu vaccine which gives some protection from this Mexican variant.

“We have identified staff who did not take up the option of a flu jab in November and are offering it them now.

“We have a list of clinical reservists and we are already contacting them to see if they will be prepared to assist. They are people like healthcare professionals and medical students.

“We are also making plans to accommodate staff on site if a pandemic breaks out.

“There are theories that the virus is mutating as it spreads worldwide and losing its virilent strain, making it easier to treat. There is also a theory that healthcare in this country is better than in Mexico, so people will benefit from that better treatment.”

Mr Bleetman added: “The emphasis will be to only admit those who need to go into hospital and put them in a safe area. If swine flu spreads then we have plans on treating people safely in the community with anti-viral drugs.

“Heartlands will initially take the most serious cases but if it spreads quickly, other hospitals will need to admit patients as well.

“Over the next few days we will be testing our plans for major incidents again, especially looking at how we support local residents and our staff should we face a major flu outbreak.”

Prime Minister Gordon Brown said Britain was “among the best prepared countries in the world” with enough of anti-viral drug Tamiflu for half the population if they became ill.

So far 152 people are thought to have been killed in Mexico by the virus, which is caused when the H1N1 strain associated with pigs crosses over to the human population.

Outbreaks have also been confirmed in Scotland, the United States, Canada, Spain, New Zealand and Israel.