National planning assumptions have been updated in line with the latest data on the severity of the current H1N1 strain.
The assumptions represent the scenario the NHS needs to prepare for, Sir Liam said.
Plans will now be based on the assumption that there could be 19,000 deaths. In July, a figure of 65,000 was suggested by government officials.
The figures are based on up to 30 per cent of people catching swine flu and 0.1 per cent of those dying as a result of infection.
The estimates take no account of the possible impact of vaccination on the spread and severity of the disease, because of uncertainties around delivery and licensing of the vaccine, the DoH said.