REUTERS/Denis Balibouse

GENEVA - The World Health Organisation (WHO) kept its pandemic flu alert at the second highest level on Friday but said that future changes would reflect how severe an outbreak was as well as how widespread

The U.N. agency has been weighing how to revamp its pandemic alert scale to reflect both the severity of the flu as well as its geographic spread around the world.

This follows criticism that it may have caused undue panic about the new strain whose effects have been mainly mild apart from in Mexico, where it is known to have killed 103 people.

There was a broad consensus on the importance of including information on severity in future announcements, said a statement issued after flu experts held hour-long talks.

The experts, meeting as WHO's emergency committee, made recommendations on a number of factors to be taken into account to assess the severity of an epidemic, it said, without giving details.

WHO's top flu expert Keiji Fukuda said this week that one idea was to add three severity notches to the highest marker of 6, so the overall level can reach the peak even if the flu's effects remain moderate, and then be adjusted again later if the virus causes more serious health problems.

The experts also maintained their advice against closing borders or restricting international travel to try to halt the continued spread of the H1N1 influenza virus, measures deemed ineffective.

Production of seasonal influenza vaccines should also continue for now, as work proceeds on developing a vaccine against the new strain, widely known as swine flu, it said.

The meeting, convened at the request of WHO Director-General Margaret Chan, did not consider crossing the threshold to the highest phase 6, according to WHO officials. That issue had not been on the formal agenda.

WHO's pandemic scale remains at the second-highest level, phase 5 on a scale of 1 to 6, meaning a pandemic is imminent.

Before Friday's changes, the WHO would have had to confirm sustained spread of the virus in one country in another region besides North America to declare a full-blown pandemic, although officials had made it clear they were already looking at how severe the epidemic was before going to the top level.

Earlier, WHO spokesman Gregory Hartl told Reuters: The director-general will use the occasion to ask the emergency committee members -- the 'flu gurus' around the world -- how and if we should have some sort of severity index within phase 6.

The experts discussed the latest findings about the virus and reviewed measures under WHO's International Health Regulations, which require countries to report promptly on outbreaks and intensify their surveillance for unusual signs.

The new strain has infected 21,940 people in 69 countries, killing 125 of them, according to the WHO. Mexico, the United States and Canada have borne the brunt of the illness and a case was confirmed in Saudi Arabia for the first time.

Fukuda, the WHO's acting assistant director-general, said on Tuesday that the virus' spread in Australia, Britain, Chile, Japan, and Spain had nudged the world closer to a pandemic.

(For the WHO statement go to here )

(Editing by Jonathan Lynn)