GENEVA - The World Health Organization (WHO) is on the verge of declaring the first influenza pandemic in more than 40 years, but wants to ensure countries are well prepared to prevent a panic, its top flu expert said on Tuesday.

Keiji Fukuda, acting WHO assistant director-general, voiced concern at the sustained spread of the new H1N1 strain -- including more than 1,000 cases in Australia -- following major outbreaks in North America, where it emerged in April.

Confirmed community spread in a second region beyond North America would trigger moving to phase 6 -- signifying a full-blown pandemic -- from the current phase 5 on the WHO's 6-level pandemic alert scale.

The situation has really evolved a lot over the past several days. We are getting really very close to knowing that we are in a pandemic situation, or I think, declaring that we are in a pandemic situation, Fukuda told a teleconference.

Fukuda said a move to phase 6 would reflect the geographic spread of the new disease.

It does not mean that the severity of the situation has increased or that people are getting seriously sick at higher numbers or higher rates than they are right now, he said.

A decision to declare a pandemic involved more than simply making an announcement, he said. The United Nations agency had to ensure that countries were able to deal with the new situation and also handle any public reaction.

One of the critical issues is that we do not want people to 'over-panic' if they hear that we are in a pandemic situation. That they understand, for example, that the current assessment of the situation is that this is a moderate level, Fukuda said.

The WHO and its 193 member states are working hard to prepare for a pandemic, for instance developing vaccines and building up supplies of anti-viral drugs, he said.

The disease, which has infected over 26,500 people in 73 countries, with 140 deaths, has been most severe in Mexico, which has reported the highest number of fatalities, more than 100. These include infections in otherwise healthy young people.

PRESSURE ON HOSPITALS

A very real danger after declaring a pandemic was that hospitals could be overwhelmed by people seeking help when they did not really need it, while other patients requiring emergency treatment risked being neglected, according to Fukuda.

In earlier pandemics, in earlier outbreaks, we have often seen that people who are in the category of being worried but who are not particularly sick, have overrun hospitals, he said.

Since the new flu strain first appeared, many people have stopped eating pork, pigs have been culled in some countries, trade bans on meat imposed, travelers quarantined, and some countries have discussed closing borders.

These are the kinds of potential adverse effects that you can have if you go out without making sure people understand the situation as well as possible, Fukuda said.

Combining human, avian and swine viruses, the new strain has been dubbed 'swine flu', although scientists say this is misleading and stress there is no risk from eating pig meat.

The world is better prepared but also more vulnerable to the adverse effects of a flu pandemic since the last one occurred in 1968, due to the speed and volume of international travel.

An H3N2 virus caused an estimated 1-4 million deaths at the time, and became known as Hong Kong flu. But Fukuda said the WHO would not name the new disease after a country or animal to avoid misleading stigmas.

He voiced concern that Canadian Inuits had suffered disproportionately in the current outbreak, often needing hospitalization. It was not clear if this was due to higher levels of underlying chronic disease, genetics or poverty.

Inuit populations were very severely hit in some of the earlier pandemics. This is why these reports raise such concerns to us, he said.

(For a WHO note on its pandemic alert scale go to:

here )

(Additional reporting by Jonathan Lynn; Editing by Mark Trevelyan)

Australia Mexico Medicine