Vulnerable people who have not had a flu vaccination, including the elderly and the chronically-ill, were yesterday urged by the Department of Health to see their GPs amid rising fears of a pre-Christmas epidemic.
Figures due out later this week are expected to show a rapid rate of increase of flu and flu-like illness, particularly in central and southern England, after GPs reported thousands of extra calls over the weekend.
The incidence of infection was last week running at 90 cases per 100,000 of the population, up from about 60/100,000 the previous week. The expected incidence at this time of year is around 50/100,000.
Dr Douglas Fleming, director of the Royal College of General Practitioners' flu monitoring bureau in Birmingham, said that reports of an epidemic were "premature". The recently revised threshold for a moderate epidemic was 250 cases/100,000, he said, and the real epidemic threshold was over 400/100,000.
However, Dr Fleming urged people who have coughs and colds and may be harbouring the virus to avoid contact with babies, the frail and elderly, asthmatics, bronchitics and other at risk groups. "Individuals cannot easily prevent it but those who have got it can prevent spreading it," he said.
The RCGP bureau collates reports from 93 GP practices covering about 700,000 patients. Latest figures show that in central England there were 120 cases per 100,000; 82 in the South; and 58 in the North. In East Anglia, one in four children in some areas have been off sick with flu- like symptoms.
A spokesman for the Department of Health said the current vaccine would protect against the most common viral strain now being reported which is A/Johannesburg, named after the city where it was first isolated last year. There are around 6 million vaccine units available, with priority given to at risk groups and those in residential homes.
Major influenza epidemics and pandemics (a global epidemic) are largely unpredictable and occur when there is a fundamental change - known as genetic drift - in the structure of the virus, producing a strain to which few people are resistant. This tends to happen every 10 years or so, although minor changes in viral structure can also cause havoc.
During the 18th and 19th centuries there were about eight influenza epidemics; during the winter 1889/90 it is estimated that more than 10 million people died worldwide.
The worst flu pandemic on record was that caused by the infamous Spanish flu which killed 20 million worldwide and led to widespread panic. In Chicago police arrested people who sneezed in the street, and in Australia it was an offence not to wear an anti-microbe mask.
In 1957 Asian flu claimed one million lives worldwide; 11 years later Hong Kong flu killed 700,000. At its peak there were around 900 cases per 100,000 of the population and 4,000 deaths per week.
In 1976, a combination of Australian and English strains of the virus took their toll in Britain in January and February. The last epidemic year was 1989 when cases started to increase between mid to late November. The outbreak peaked at around 538 cases per 100,000 and between 19,000- 25,000 deaths were eventually attributed to flu. In a non-epidemic year there are between 3,000 and 4,000 deaths from flu.
A mini-epidemic in 1993 made headlines, but attention was focused more on a vaccine shortage due to bureaucratic bungling than on the number of cases or deaths. The outbreak, due to the Beijing A strain, peaked at 235 cases per 100,000.