Picture this:

Hong Kong has virtually shut down as hospitals are inundated with thousands of suspected bird flu cases.

After months of warnings from health officials, an avian influenza virus capable of rapid human-to-human transmission is a reality. The virus has mutated quickly from an earlier form passed from poultry to people.

The announcement by the World Health Organization (WHO) that the virus is now a pandemic, affecting numerous countries including Hong Kong, has prompted the Secretary of Health, Welfare and Food to elevate the city's response level to Emergency, effectively mobilizing the city's stockpile of anti-viral medication in an attempt to slow the virus' progress.

Despite drafting a plan conceived precisely for such a scenario, the government is overwhelmed on all fronts, with more than a quarter of the city infected.

Because the virus causes few initial symptoms, it is proving far more infectious than SARS.

Seventy percent of those infected could die without anti-viral medication, and even with medication, the prognosis for recovery is grim.

With practically everyone in the city a potential carrier, the government is unable to implement the quarantine measures that proved so useful in containing SARS. Its call for the closure of all schools and a ban on all non-essential public gatherings will do little to improve the situation in the city as most people, including carriers who have yet to display symptoms, are already staying home of their own accord for fear of infection.

The Department of Health has commandeered large amounts of television and radio broadcast time to educate the public in self-management of influenza-like illnesses, including advice about how and when to get treatment.

Over the next few days, increasing numbers of people are likely to feel the effects of the virus and seek medical attention.

The health care system, already seriously strained by the crisis, could buckle under the pressure.

Health officials have long since abandoned confirmation testing on suspected carriers, realizing that the sheer number of people with flu-like symptoms makes the procedure too burdensome and unnecessary at such a late stage.

The government is struggling to keep the city running with a skeleton crew of health, transport, tele-communications, law enforcement, and utilities workers while it buys time and waits for the virus to run its course.

Despite the efforts of scientists worldwide, a vaccine is at least six months away.

Even then, the vaccine may not be entirely effective against this terrifying new strain of human bird flu.

Meanwhile, with many top government officials themselves infected, many of the city's services are running on autopilot with little supervision.

Could this nightmare scenario occur?

Officials at the World Health Organization take it very seriously. If the present H5N1 avian influenza strain were to mutate into a virus capable of rapid person-to-person transmission, the picture painted above is likely, according to WHO spokesman Peter Cordingley. So likely that an emergency plan aimed at dealing with broad territory-wide paralysis and significant deaths from pandemic influenza has already been drawn for governments worldwide to adopt.

Cordingley says governments should prepare for scenarios where ``one third of the workforce is sick or too frightened to leave home'' and come up with contingency plans to keep such basic services as transport and telecommunications running while the virus is still active.

Hong Kong, where the first instance of direct bird-to-human transmission of the virus was documented during an outbreak of avian influenza among poultry in 1997, has taken the lead in creating an emergency plan of its own.

Designed to match the guidelines suggested in the WHO's emergency plan, Hong Kong's ``Preparedness Plan for Influenza Pandemic'' is broken down into three response levels - Alert, Serious and Emergency. The Emergency response level will be declared if the existence of an easily transmitted human-to-human strain is confirmed, or an influenza pandemic is already under way.

According to Department of Health spokesman Edmond Chow, Hong Kong has a stockpile of 3.7 million doses of the anti-viral drug Tamiflu for emergency use in the event of a pandemic - enough for more than half the city. It wants to boost the stockpile to 20 million doses within the next 12 months.

Cordingley believes Hong Kong is doing everything it is supposed to do to prepare for the worst. He has nothing but praise for its resolve to deal with the influenza threat.

``Hong Kong is among the best in the world at this business,'' he says.

The city is also doing its part to help other Asian countries that lack resources or expertise in the area. ``Hong Kong is well placed and is already helping its neighbors,'' he adds.

In the area of preventative measures, the city has taken dramatic steps to ensure that new strains of bird flu don't come from its own poultry. New influenza strains capable of spreading through a human population will likely emerge overseas before emerging from inside Hong Kong.

Professor Leo Poon Lit-man, an expert in influenza viruses at the University of Hong Kong, says the government has done ``a fantastic job'' reducing the risk of infection from poultry with a host of effective screening and transportation measures.

But is it all enough? Would we be able to stop bird flu if it hits Hong Kong?

Despite the preparedness plan, stockpiles of anti-viral medications and aggressive prevention measures, there is little that could be done if a pandemic reaches Hong Kong. A rapidly mutating virus moving at will through the world would be almost impossible to stop at the city borders.

``There will be nothing that can stop it,'' Cordingley says.

Adds Poon: ``If [the virus] adapts in humans, I don't think we'll be able to control it. It will be out of hand.''

In the event of an influenza pandemic, the plan should be effective in at least keeping the city running rather than lowering the infection rate.

Says Cordingley, the quarantine measures that proved effective in controlling SARS would be ineffective in an influenza pandemic. The bird flu virus' short incubation period of two to three days means significant parts of the population would be infected quickly and show few visible symptoms, frustrating efforts to isolate high-risk groups and prevent further infection.

It is unlikely that any isolation ward could contain the infection. Nor is it likely there would be an epicentre of the disease, as the Amoy Gardens housing estate was in the SARS epidemic. Facemasks, however, would be of help.

``You can [implement quarantines] with SARS, but you can't do it with influenza,'' Cordingley says.

``How are you going to quarantine people if you don't even know who has it?''

Surveillance activities such as identifying potentially infected inbound travelers at airports would be irrelevant should the virus reach Hong Kong.

Equally bleak is Cordingley's belief that government plans to provide anti-viral medication to the infected would have limited impact since the medications currently available can only ease the symptoms of infection. A more effective vaccine would take months to create.

``Work [on the vaccine] would not start until the pandemic happens,'' after countless people had already been infected, he adds.

And the chances of a doomsday virus with rapid person-to-person capability emerging?

Cordingley says we are two quick mutations away from such a virus. The current H5N1 virus, which has shown only moderate ability to transmit from birds to humans, must first mutate into a strain that passes easily from poultry to the public, then mutate into a strain that can transmit as easily between people as common flu does now.

``We just don't know,'' says Poon, referring to if or when those mutations will happen.

``We really don't know what's going to happen in the future.''