STOCKHOLM (Reuters) - The H1N1 pandemic flu virus could kill up to 40,000 people across Europe and be followed by seasonal flu waves that could kill the same number, European health experts said on Friday.

Dynamo Kiev's fans wear face masks as a preventive measure against the H1N1 flu during their Champions League soccer match against Inter Milan in Kiev November 4, 2009. REUTERS/Gleb Garanich

The Sweden-based European Center for Disease Prevention and Control said epidemics of H1N1, known as swine flu, were now affecting almost all countries in the European Union but it could not predict how intense the peaks would be.

What was certain, it said, was that the pandemic would continue to kill thousands and put many patients into intensive care as the northern hemisphere’s winter sets in.

“All European countries will be affected, and this will put considerable stress on healthcare systems,” said ECDC director Zsuzsanna Jakab.

The ECDC, which monitors disease in the European Union and European free trade area (EFTA), said it was hard to predict what the mix of pandemic and seasonal flu viruses would bring but there was a risk of seasonal flu epidemics “early in 2010 when the pandemic waves have passed.”

Angus Nicoll, the ECDC’s flu coordinator, said in non-pandemic situations, seasonal flu could kill up to 40,000 people in Europe -- and H1N1 could do the same.

“That is not a trivial number,” he said. “And the fact that H1N1 is happening in younger adults, pregnant women and people without risk factors ... makes it feel different.”

RISKS AND DEATHS

The ECDC said experience from the United States and the southern hemisphere showed pregnant women with the virus are 10 times more likely to need intensive care than those with no risk factors. Those with asthma and chronic respiratory diseases have three times the risk and the very obese six times the risk.

But it also said evidence so far shows some 20 to 30 percent of H1N1 deaths are among healthy young people.

The ECDC’s latest daily update said all 27 EU and four EFTA countries have cases of H1N1 pandemic flu and there have been 389 deaths linked to H1N1 in the region since April, including 154 in Britain, 73 in Spain, 25 in Italy and 22 in France.

The ECDC’s global toll showed 6,005 fatal cases of H1N1 have been reported. The WHO, which updates its figures weekly, said on Thursday 5,712 people have died worldwide since H1N1 was discovered earlier this year.

The ECDC said the numbers of fatal cases associated with pandemic flu were “likely to be gross underestimates” as access to healthcare and lab tests varied from country to country.

GlaxoSmithKline and Sanofi-Aventis are among some 25 companies making pandemic vaccines, while other drugmakers including Roche are making antiviral therapies for use as frontline H1N1 treatment.

Nicoll said vaccination programs which started in some European countries in recent weeks were vital to protecting those most at risk but had come too late to halt the disease.

“We’re not trying at this stage to protect the whole of society with the vaccines. The strategy is to protect the vulnerable.”