NZ prepares for possible flu pandemic

The 7am radio bulletin shocks you awake with the latest death toll. On the bus, the surgical masks make everyone look the same. A queue is already forming outside your pharmacy, one of the few shops still open.

Those queuing hope to buy some of the last remaining stocks of anti-virals. Fat chance. There's been little in the country for a fortnight, except the government stockpile.

It has been 20 days since the World Health Organisation declared it an influenza pandemic; 18 since the first cases started turning up at Auckland clinics - and dying.

It is a frightening scenario, but one that gains credence from health experts' predictions of a pandemic, the history of past worldwide flu outbreaks and descriptions in new phone books of how to prepare for a pandemic.

No one knows when the next flu pandemic might occur, but by the rough guide that three occurred in the 1900s and the last was 37 years ago, the next one is anticipated any time. Likewise, no one knows how severe it might be, but officials are preparing for the worst.

The World Health Organisation (WHO) says between 2 million and 7.4 million is a reasonable working forecast.

New Zealand predictions are that between 1600 and 3700 people will die, based on between 15 and 35 per cent of the population becoming ill.

In a severe pandemic, hospitals are likely to be quickly overwhelmed by huge numbers of patients and staff being off sick. Schools, pre-schools and universities would be forced to close, public events could be banned and many shops, offices and factories would close.

Christchurch virologist Dr Lance Jennings says a pandemic flu could land in New Zealand within hours of an outbreak because of air travel, although the country's geographic isolation could act as a natural barrier if tight border controls were in place.

The last three human flu pandemics - 1918-19, 1957 and 1968 - all arose from influenza in birds which is why virus experts are watching the progress of the present outbreaks of H5N1 flu in birds mainly in Asia and emphasise the need to kill affected flocks rapidly.

Romania and Turkey are the latest countries to cull affected birds.

The 1918 Spanish flu pandemic swept the world for 18 months.

It killed between 40 million and 50 million people. In New Zealand, it infected between one-third and half of the population and killed more than 8000.

Hospitals overflowed and makeshift hospitals had to be opened in schools, halls and tents.

The Government shut schools and other facilities to stop public gatherings where the virus could be spread by coughing and sneezing.

Citing a paper this month in the international journal Nature, Jennings says the 1918 pandemic might have been caused by an avian virus which adapted to humans.

"The 1957 avian influenza virus was a mixture of the 1918 virus with three new genes from avian species, from ducks. The 1968 virus was the 1957 virus with two new genes from ducks.

"So the 1957 and 1968 viruses emerged from a re-assortment process and it is postulated that that re-assortment of genes occurred within pigs.

"It appears the 1918 virus emerged directly from an avian virus which was adapted to human infection and can be transmitted efficiently from human to human.

"Because it was a totally new virus and there was possibly no natural immunity, it may have been the cause of the severe outcome of the 1918 pandemic. The 1957 and 1968 pandemics were a lot milder. That may have been because there is some residual immunity or protection within the population so while you still got explosive outbreaks, they were not associated with the high mortality of the 1918 pandemic.

"What we are really concerned about now is the H5N1 when it does cross the species barrier and infect tigers and cats, as we have seen. In humans it has a very high mortality rate of about 52 per cent."

If it adapted to efficient human-to-human transmission, "you could see an outcome similar to 1918".

While the virus has infected millions of birds, it has so far infected only 117 humans since late 2003 - as far as authorities know - of whom 60 have died, a high case/fatality rate.

But the virus is not yet easily transmitted between humans, a necessary condition for a pandemic.

Thailand last year reported a "probable" case of human-to-human transmission: a mother who may have been infected by close contact with her sick daughter, but also said she might have been infected by an "environmental source".

The WHO says " ... evidence to date indicates that transmission of the virus among humans has been limited to family members and that no wider transmission in the community has occurred".

Bird flus are among the A strains of the virus. Influenza A strains also cause winter outbreaks of human flu, and protection against them and B strains is included in the annually updated flu vaccine.

In New Zealand, flu kills more than 100 people a year. Symptoms start suddenly and include a high fever, headache, aching muscles, cough, sore throat and runny nose. It is spread mainly by coughing and sneezing, but also through touching door handles or other surfaces infected with mucous then touching your eyes or mouth.

Pandemic flu is spread the same way and causes the same symptoms. The differences are that many more people become sick because they have no immunity to the novel strain and the symptoms can be more severe.

Some who caught Spanish flu collapsed within hours and died the same day.

In birds, flu can replicate in the gut as well as the respiratory tract, but in humans it infects only the respiratory system.

The virus' surface proteins fit snugly into receptor sites on certain cells in humans' upper airways.

"You get a bushfire spread through those cells," says Jennings. "The incubation period of 24 to 72 hours results in initially damage to those cells. It triggers an immune response which responds to the damaged cellular material and activates a cascade of responses. This results in the signs and symptoms associated with infection."

Preparation for a pandemic has sped up in New Zealand this year. Measures include advice sent out to GPs and the public, district health boards submitting their plans to a national review committee, and the Government spending $26 million to stockpile 835,000 courses of anti-viral tablet Tamiflu and $6.3 million on extra clinical supplies.

A vaccine against the as-yet unknown virus also figures in the ministry's planning, even though it would take months to make.

Public health director Dr Mark Jacobs said one of the first strategic goals was to keep the virus out.

"One of the main reasons is to buy time to get the vaccine. If we can get the vaccine into the country and immunise people before the pandemic strikes we are not going to get big impacts from the pandemic."

But if that could not be done before the first wave of the pandemic, it could head off a second wave.

Tamiflu can be used to prevent infection or to shorten the course of the flu, although some doctors say there is no proof it will work against the next pandemic flu virus.

The ministry's stockpile will be enough for one course to be given to 20 per cent of the population.

It has not decided who will be allowed to use its Tamiflu, but healthcare workers are likely to be first.

A January cabinet paper lists health and ambulance workers first; police, fire and defence second; key civil infrastructure workers third; and the agricultural, transport and manufacturing workforces fourth, although no priority order is stated.

It says 720,000 courses would be enough for all of them and the rest of the population if the infection rate was 15 per cent.

But if it was 35 per cent, the upper end of pandemic plan modelling, the paper indicates there will be a shortfall of around 600,000 courses. The rest of the population will get it in order of priority.