Seasonal influenza is losing its grip.
The infection that has laid low millions of people every winter for generations, causing widespread deaths and wreaking havoc with the NHS and the economy, is at an all-time low. On present trends, this winter is set to register the lowest level of seasonal flu on record.
Figures from the Health Protection Agency show the consultation rate for flu-like illness with GPs was 15.6 per 100,000 population in England last week – half the rate for normal seasonal activity.
Throughout December and January, flu has been running at levels more usually associated with the summer months. Consultation rates have gone up slightly in the last week and experts warn that the flu season is not over yet. But, barring a sudden change, Britain will not see significant illness caused by flu this winter.
The low level of flu has surprised experts after two years dominated by the swine-flu pandemic which broke out in the summer of 2009. It caused widespread illness and over 1,000 deaths in the winters of 2009-10 and 2010-11. Intensive-care units were full and GPs were forced to turn patients away because of a vaccine shortage.
The agency was prepared for another busy flu season this winter – but it hasn't happened. The swine-flu virus H1N1, which has dominated for the last two years has almost disappeared – to be replaced by a different dominant virus, H3N2.
"You can never predict what happens with flu – but we were surprised," an HPA spokesperson said. No one has been more delighted than the embattled Health Secretary, Andrew Lansley.
In an average winter, flu causes long delays in A&E departments as sick patients queue to be admitted and NHS waiting lists for operations lengthen. But this winter – one of the quietest ever for the NHS – the number of patients waiting over 18 weeks in December is down 24 per cent compared with a year earlier.
Though Mr Lansley may lack friends as he struggles to drive his unpopular reforms through Parliament, he can at least take comfort that nature is on his side. The low for this winter's flu is the culmination of four decades of steady decline in the impact of the illness, punctuated by the occasional epidemic.
The reasons for the drop, seen chiefly in children under the age of five, are thought to be better hygiene, less pollution causing fewer respiratory infections (which provide an opportunity for the flu virus to spread), more people self-treating at home and changes in the natural cycle of the disease.
Flu vaccination, offered to the over-65s and those with chronic illnesses, may also have played a part. Though flu vaccines have been available since the 1970s, the national flu vaccination programme only began in 2000. However, the biggest fall has been seen in children, who are rarely vaccinated.
Douglas Fleming, head of the Royal College of General Practitioners' flu-monitoring service, which gathers the figures on flu consultations, said the 40-year decline was linked with improved living conditions.
He said: "The rates of nearly all respiratory infections are falling. There is much less smog, there is far less smoking and there is better hygiene. One of the greatest benefits of central heating may have been not the warmth it brings but the constant hot water." Diseases followed cycles that were sometimes unexplained. "If you look over centuries you see changes," Dr Fleming said.
"We have seen it with polio and tuberculosis. You would expect the flu virus still to infect vulnerable people but it does not seem to attack with the same ferocity."
Professor Nick Phin, a flu expert at the Health Protection Agency, said efforts to dissuade patients from going to their GP with flu were likely to have had an impact, reducing consultation rates.
He said: "It's still too early to say if this is one of the lowest flu seasons we have seen in recent years as the season is not over yet and flu is still circulating in the community."
Most severe flu epidemics had begun before Christmas but in seven winters since 1988, flu started after Christmas and in two of those years (1992-93 and 1997-98) the winter outbreak did not begin until mid-February, he said. Professor Phin added: "Fortunately we seem to have had a relatively mild flu season so far this winter, but this comes off the back of one of most severe flu seasons in recent years, when just over 600 people died from the illness.
"Seventy per cent of the people who died were in a clinical at-risk group, and as we can never predict how severe a flu season will be, we mustn't be complacent – it's vital that those at risk receive their seasonal flu jab every year.
"For most people flu is a mild and manageable illness, but for those at risk – including pregnant women, people with serious medical conditions and the over-65s – it can be fatal, and every effort must be made by health professionals to encourage these groups to take up the offer of vaccination. It's the best way to protect against flu."