By Laura MacInnis and Stephanie Nebehay
GENEVA (Reuters) - The world must be ready for H1N1 flu to become more severe and kill more people, World Health Organisation chief Margaret Chan said on Friday.
Japan meanwhile prepared major aid to poorer Asian states to fight the virus, as the approach of winter in the southern hemisphere threatened to rekindle its global spread.
The highly-infectious strain must be closely monitored in the southern hemisphere, as it could mix with ordinary seasonal influenza and mutate in "unpredictable ways," Chan told the WHO annual congress in Geneva.
"In cases where the H1N1 virus is widespread and circulating within the general community, countries must expect to see more cases of severe and fatal infections," she said.
"We do not at present expect this to be a sudden and dramatic jump in severe illness and deaths."
But she added: "This is a subtle, sneaky virus. We have clues, many clues, but very few firm conclusions."
The H1N1 flu strain, which has sparked fears of a global pandemic, is a mixture of swine, bird and human viruses that spreads easily among people.
Worldwide, it has killed 86 people -- most in Mexico -- and infected more than 11,000 in 42 countries, the WHO said.
Outside North America, the biggest concentrations of infections are in Japan with 294 cases, Spain with 113 and Britain with 112.
Russia said on Friday it had its first confirmed case of the disease and the WHO was testing two suspected cases in Democratic Republic of Congo, which would be Africa's first.
ASIAN PROJECT
Japan said on Friday it would launch a $31.85 million (20.06 million pounds) project to fight the virus in poorer Asian states when foreign ministers from Asia and Europe hold a two-day meeting in Hanoi from Monday.
Under the initiative, Japan will store anti-flu medicines like Tamiflu and Relenza and gear like masks and gowns at a warehouse in Singapore in case of a major outbreak. The WHO will decide when and where to use them.
When the project was first announced last October it was intended to counter bird flu, which has been prevalent in east Asia for several years, rather than the latest H1N1 strain.
WHO officials say Asian nations, with young populations and endemic chronic illnesses, are particularly vulnerable to the spread of the new virus.
Most of Japan's own 300 infections appear mild and officials relaxed preventive measures on Friday.
Under the new guidelines, some suspected patients can go to regular medical institutions rather than special "fever centres," and schools will not be automatically shut down.
Quarantine checks will no longer be carried out on most flights. Japan has also relaxed its travel warning for Mexico.
But Robert Booy, who heads Sydney University's immune research and surveillance centre, said more people than usual in Southern Hemisphere countries could become infected this winter and die from the new flu because of its "novelty."
"Once you have enough virus out there, evolution is simple," Booy said, adding the H1N1 virus could change to the point that it could get "nasty."
In Australia, where cases have spread across several states and two of its 11 infections were locally contracted, the government raised its flu alert level to mid-range "containment" on Friday. This would give it power to shut schools.
In Hong Kong, the epicentre of the SARS epidemic in 2003, officials were taking no chances even though it has only four cases of H1N1 so far, all apparently imported.
"If there are many patients, we will have designated clinics that will perform checkups and monitor them and administer antiviral drugs (Tamiflu) if needed. We will require them to be quarantined at home," Health Secretary York Chow said.
(Reporting by Reuters reporters worldwide; writing by Andrew Roche; editing by Philippa Fletcher)