More than 300 people are in intensive care in hospitals across Britain with flu, and European health officials say the region should act now to encourage more people to get vaccinated.
A spokeswoman for the British government's health department said a total of 302 people were in critical care beds with flu. She could not say how many had the H1N1 strain which spread around the world as a pandemic from 2009, but experts said it was likely that H1N1 would be dominant.
"From around the country, reports from frontline staff are showing unprecedented levels of hospitalisation with severe flu in high-risk adults," said Peter Openshaw, director of the Centre for Respiratory Infection at the National Heart and Lung Institute, Imperial College London.
According to the latest data from the UK Health Protection Agency, 14 people have died in Britain with confirmed H1N1 flu so far this flu season and another three have died with a strain known as flu type B. That number is expected to increase.
Angus Nicoll, a flu specialist at the European Centre for Disease Prevention and Control (ECDC), which monitors disease in the region, said the situation in the UK was as he had expected for flu season, but should nevertheless serve as a warning to other countries in Europe to prepare themselves.
"Usually flu moves from west to east in Europe....so the fact that it's starting in a western country is not that surprising, but it's quite useful," he said in a telephone interview from Stockholm, where the ECDC is based.
"This is an indication of what we are likely to be seeing in other parts of Europe not too long from now."
Experts said the evidence from Britain suggested H1N1 flu, which is also known as swine flu, was behaving much as it did last year, affecting younger adults, those in high risk groups such as pregnant women and also some children.
H1N1 flu was discovered in Mexico and the United States in March 2009 and spread rapidly across the world. The World Health Organisation said about 18,450 people died from the virus, including many pregnant women and young people. The WHO declared the pandemic over in August.
"All the evidence we have so far is that the virus has not changed," Openshaw said in an e-mailed statement. "It is affecting the same type of person as last year and still behaves like swine flu rather than normal seasonal flu (which mostly affects the over-65s)."
The ECDC is asking European governments to encourage people, especially those in high risk groups, to get seasonal flu vaccinations, even if they had the H1N1 shot last year.
Seasonal flu vaccines being offered across the world include for the H1N1 strain this year after the WHO advised it was likely to be the most dominant strain of the northern hemisphere's 2010/2011 flu season. Flu vaccines are made by several drugmakers including GlaxoSmithKline, Sanofi-Aventis and Novartis. (Reuters Health/ December 2010)