More than 600 people were on Saturday awaiting test results to find out whether they have contracted swine flu as the number of those infected with the potentially fatal virus rose to 13, AFP reported.
On Friday, health officials confirmed they had discovered the first two cases of people being infected with the virus who had not travelled to Mexico, the epicentre of the outbreak.
Graeme Pacitti, 24, who comes from from Polmont, about 20 miles west of Edinburgh, tested positive for the H1N1 virus after coming into contact with a friend who had fallen ill after going on honeymoon to Mexico.
Barry Greatorex, 42, from Chipping Sodbury in Gloucestershire, was also found to have contracted the virus from a workmate who had recently come back from Mexico.
"The first non-imported cases of swine flu have been confirmed in England and Scotland," the government's chief medical advisor Liam Donaldson said late on Friday.
"The infection appears to have been acquired by person-to-person spread within the United Kingdom.
"Until now, cases were confined to people who had themselves recently come back from Mexico. The person in the southwest is being treated with Tamiflu."
There are now 10 confirmed cases in England and three in Scotland, officials say -- all said to involve mild symptoms.
An official said the case in southern Gloucestershire was not linked to that of a 12-year-old girl in the same region who was diagnosed with the illness after flying in from Mexico last week on the same flight as the honeymoon couple.
Iain and Dawan Askham, the honeymooners from Scotland who were among the first thought to have caught the virus, were released from hospital on Thursday after spending five nights in quarantine.
The 12-year-old's school has been closed and will not reopen until May 11, with students in her year also given a flu remedy.
The swine flu virus originated in Mexico, where it has killed at least 15 people and infected more than 320.