HC Deb 10 February 2000 vol 344 cc258-9W
Mr. Maclean

To ask the Secretary of State for Health(a) how many cases of influenza per 100,000 there have to be for an influenza outbreak to be defined as an epidemic and (b) how many cases of influenza per 100,000 there were on 11 January. [105677]

Yvette Cooper

The epidemiologists' definition of an epidemic is an increase in the frequency of occurrence of a disease in a population above its baseline level for a specified period of time. The term epidemic can be used when describing the pattern of either infectious or chronic diseases in the population.

Administrative definitions can be set for diseases in which an arbitrary threshold is selected above which the term "epidemic" is applied. In the case of influenza, the Department introduced in 1996 an administrative definition of an "epidemic" for a rate of consultation (with a sample of general practices) of 400 per 100,000 population in a week.

Such influenza activity in England is thus monitored through the Royal College of General Practitioners (RCGP) sentinel surveillance scheme. This records the number of first visits to a general practitioner with influenza-illness. Other respiratory illnesses prevalent at this time of year are recorded separately.

This system does not and cannot measure the real incidence of influenza since it is restricted to those people who visit their general practitioner. This year a major campaign was run to encourage people to choose their own remedy, to consult a pharmacist and to use NHS Direct, as alternative sources of advice.

The severity of the disease itself can also vary from year to year. This year the elderly have been particularly affected by the complications of influenza. The level of cases of acute bronchitis, a serious complication of influenza, is the highest the RCGP surveillance system has seen for 15 years. In describing epidemics some other countries formally include measures of severity in the definition of an epidemic. For example, the United States declares an epidemic when the proportion of deaths due to pneumonia and influenza passes a certain threshold.

The latest confirmed figures from the RCGP show an overall rate of consultation of 236 per 100,000 for England for the week ending 16 January 2000.