The Government's chief scientific adviser has said swine flu could effectively make its last stand in the UK within weeks.
Professor John Beddington said a second wave of infections was expected “not much before October at the earliest”.
Thereafter research and epidemic modelling suggested the virus would be weakened.
“You can get infections coming back in a number of waves but it's likely that the next one will be larger than any subsequent ones,” Prof Beddington told the British Science Festival at the University of Surrey.
Members of the Scientific Pandemic Influenza Advisory Committee (Spi), which advises the Government on flu pandemics, is due to meet today for a swine flu update.
“What is likely to happen will depend on a number of things, firstly the number of unreported cases,” said Prof Beddington.
“Whether it comes in October early and at a fairly high level, or in more moderate waves later in the year, is hard to predict.”
Long term, the fate of the virus would depend on how it competed with normal seasonal flu, he said.
It was possible swine flu might become the new “default” seasonal flu.
“There may be some quiescence of incidence in summer next year after which it could come back as a normal seasonal flu; we don't know, it's early days,” said Prof Beddington.
There were 17 new cases of laboratory confirmed swine flu during last week, the Department of Health in Northern Ireland yesterday stated.
The total number of laboratory confirmed cases on September 9 was 189. The overall number of swine flu hospitalisations was 78 at this point, with one death related to the virus to date.
Health Minister Michael McGimpsey said: “As part of our plans and pandemic preparedness, work is on-going locally and nationally to plan for increasing critical care capacity to cope with additional demand during the expected surge of cases in the autumn.”