GENEVA - The spread of H1N1 flu in Australia, Britain, Chile, Japan and Spain has nudged the world closer to a pandemic, the World Health Organisation said on Tuesday.

The newly-discovered strain had caused more infections than seasonal influenza at the start of Chile's flu season, raising concern about how it would spread in the southern hemisphere, according to Keiji Fukuda, the WHO's acting assistant director-general.

The virus has mainly affected people aged below 60 and caused 117 deaths worldwide, including some otherwise healthy people, he said. For now, the WHO's pandemic scale remained at the second-highest level but the threshold may soon be crossed.

Globally we believe that we are at Phase 5 but we are getting closer to Phase 6, Fukuda told journalists. The future impact of this infection has yet to unfold.

He added: It is probably fair to call the situation something like moderate right now. We do have some hesitation to call the situation mild.

The new flu, a mixture of swine, bird, and human viruses, remains most prevalent in North America but has infected nearly 19,000 people in 64 countries, according to the U.N. agency's latest toll, which tends to lag behind national figures but is considered more secure.

Fukuda said that, while many countries had reported only a small number of infections linked to people traveling to the disease epicenters of Mexico and the United States, others were starting to see more sustained patterns of infection in schools, offices and neighborhoods.

There are a number of countries that appear to be transition, moving from travel-related cases to more established community types of spread, he said, citing Australia, Britain, Chile, Japan and Spain as examples.

We still are waiting for evidence of really widespread community activity in these countries. It is fair to say that they are in transition and are not quite there yet which is why we are not in Phase 6 yet, Fukuda said.

PANDEMIC PATTERNS

Experts say it is nearly impossible to gauge how widespread the H1N1 flu has become because many patients suffer only mild symptoms and are not formally diagnosed, treated and documented.

We don't know the full number of people who are infected across the entire spectrum. So right now it appears that the number of severe illnesses appears relatively limited, but again we don't have a perfectly good handle on the numerator and the denominator of what we are seeing, Fukuda said.

In Chile, which is just entering its normal flu season, Fukuda said the H1N1 variety appeared to be eclipsing other strains in circulation.

Most of the influenza viruses that they are seeing so far are the new influenza A-H1N1 viruses, he said. They are seeing many fewer of the normal seasonal influenza viruses and the majority of viruses are the H1N1.

We need to see whether this pattern holds up in other countries, Fukuda continued. This is one of the patterns that have been seen with earlier pandemics so I think it bears very close watching.

The WHO consulted more than 30 public health experts from 23 countries on Monday about how to revamp its pandemic alert scale to reflect both the severity of the flu and its geographic spread, as many governments have asked it to do.

One idea, Fukuda said, was to add three severity notches to the highest marker of 6, so the overall level could reach the peak even if the flu's effects remained moderate, and be adjusted later if the virus caused more serious health problems.

All pandemics are not the same. Some pandemics can be mild, other pandemics can be more severe, he said, also stressing that the same virus could have drastically different effects in different countries and regions, for instance posing greater risks in poor or disease-stricken communities.

Radical actions imposed in immediate response to the outbreak, including quarantines, trade bans and the culling of swine certainly didn't make people safer and caused undue concern about the safety of animals and food, Fukuda said.

Some of the things that we would like to do is improve how we are able to communicate information, how we are able to provide guidance on what can be done in this situation so that actions which are really unnecessary and potentially anxiety provoking and unhelpful can really be modified or curtailed.

(Additional reporting by Jonathan Lynn; editing by Andrew Dobbie)

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