Swine flu contained but officials still on guard

New Zealand has contained its outbreak of swine flu but health officials remain concerned that it could flare up in a more dangerous form in the future.

The new virus, H1N1 SW1, can be treated with anti-virals such as Tamiflu and Relenza, but because of the history of influenza pandemics, virologists and health authorities are wary.

Experts still have much to discover about the new strain, but their picture so far is that it spreads very easily between humans, more easily than seasonal flu, and kills around four in every 1000 who catch it.

The deaths, outside Mexico where the outbreak began, tend to be among those with other health problems.

This contrasts with the last potential pandemic influenza, an H5N1 bird flu, which is difficult to transmit between humans but kills at least half of those it infects.

The new swine flu first appeared in New Zealand last month after a group of Rangitoto College students returned from Mexico.

College teacher and spokesman Peter Harwood said yesterday that the 22 students and three staff were all back at school and everyone had "moved on".

In letters to Government agency chiefs this week, the Ministry of Health predicted New Zealand might experience either widespread mild to moderate infection, or in a second wave, a more severe illness.

"Our successful containment efforts so far provide an opportunity for district health boards to finalise your operational plans for managing an escalation, something which WHO [the World Health Organisation] believes is imminent."

The ministry also suggested fine-tuning of pandemic plans as the nature of the swine flu became clearer and highlighted Mexico's seven-day shutdown to try to break the cycle of virus transmission, suggesting similar measures could be required in New Zealand.

"Some of the key decisions of the [pandemic] plan are potentially sweeping in nature, and if circumstances suggested they were necessary ... we would not hesitate to recommended to Cabinet that they be taken, and possibly at short notice."

A leading virus expert, Dr Lance Jennings, of Christchurch, says the fear remains the unpredictability of influenza viruses.

"Our concern with H1N1 SW1 swine flu virus is that it's going to evolve and emulate the 1918 Spanish influenza virus where we had a mild wave followed by a wave caused by a virus which was [far] more virulent and had with it the associated high mortality among young children and young adults."

Of concern for New Zealand is the WHO's fear that the chances of the virus mutating could increase in the Southern Hemisphere as it enters the winter flu season.

Dr Jennings said this was because arriving in the flu season - when conditions meant there was more flu virus circulating - might facilitate the new virus' transmission, its evolution, or its acquisition of genes from seasonal flu viruses.

THE GLOBAL REACH

Laboratory-confirmed cases in 40 countries

Worldwide: 9830 cases, 78 deaths

New Zealand: 9 cases, no deaths

Canada: 496 cases, 1 death

Japan: 159 cases, no deaths

Mexico: 3648 cases, 72 deaths

United States: 5123 cases, 5 deaths

CONTAINMENT

* In New Zealand, authorities consider they have successfully contained the outbreak.

* Border controls are still in place to detect, isolate and treat suspected cases as planes arrive.

* New Zealand had 21 suspected cases yesterday and 12 people were in isolation and being treated with Tamiflu.

* But authorities are still planning for "sweeping" closures of public facilities and isolation of regions at short notice if necessary to break the infection cycle.

* In Japan, more than 4000 schools and colleges have been closed and companies are discouraging unnecessary travel.

* Mexico closed many business and schools in late April, but by this week all students were back in class.