The swine flu outbreak has so far been "contained" in Britain, Health Secretary Alan Johnson has said.
Three more cases of swine flu were later confirmed by the Department of Health, bringing the total number of victims in the UK to 18.
Mr Johnson acknowledged there would be more cases in the UK and the authorities had to be prepared for the possibility of a more serious "second wave" when the colder, wetter weather returns in the autumn.
"Our evidence from all previous pandemics is that you get two phases. You get a first wave that is often very mild and then you get a much more serious wave that comes along in the autumn and the winter," he told BBC1's The Andrew Marr Show.
"So we have to not just deal with this outbreak now, but prepare, perhaps, for a second phase further down the line."
Although the World Health Organisation has declared a phase 5 alert level - one step short of declaring a pandemic - Mr Johnson said that the measures taken in the UK had proved effective in limiting the spread of the disease.
"Pandemic just describes the geographic spread, it doesn't describe the severity. So far ... I think it is contained," he said.
"There will be more cases. There are 15 confirmed at the moment, that will go up, there is absolutely no doubt of that.
"But at the moment all the evidence is that we can confine it, contain it, and treat it effectively."