Nor is it simply a problem for just one season. WHO says that for at least the next decade there must be continuous monitoring, response and mitigation by control measures including education, vaccination and changes to animal husbandry and food production. It also means that each outbreak must receive an appropriate emergency response.

Because the flu is widespread among the migratory bird populations, there are fears that it will be spread to domestic bird populations around the globe. In both the Netherlands and Germany, farmers are now obliged to keep their birds indoors.

Australia is host to many migratory birds that fly in to avoid the rigours of the northern hemisphere winter. For example, tens of thousands of geese, gulls and cormorants that summer at Lake Qinghai in western China have begun to leave on their trip south to India, Bangladesh, Myanmar and eventually Australia

Avian flu was detected at Lake Qinghai last April. By May, it had spread through the bird population of the lake, killing thousands in what one ornithologist called “the biggest and most extensively mortal avian influenza event ever seen in wild birds”.

So far, there have been 112 recorded cases of people infected with the H5N1 bird flu - more than half of whom have died. Fortunately, H5N1 has not acquired the ability to spread easily from person to person. But its fatality rate of 55% outstrips any human flu epidemic on record, including the Spanish flu of 1918-19 that swept the globe killing at least 50 million people.

The Spanish flu was so-called because that country had a particularly grim time with the pandemic, but most influenza epidemics originate in Asia. In fact, it was in the Asian flu epidemic of 1957 that the linkage between the human strain and bird-life was first identified.

It was discovered by New Zealand-born scientist Robert Webster, who at 72 now heads a research team at St Jude’s Children’s Research Hospital in Memphis. In an interview with The Washington Post, Webster said he believed an avian flu pandemic “is inevitable. One of these is just going to blow”.

If we did experience a full-blown pandemic, the economic and investment implications would dwarf anything we have seen in the way of a systemic shock since the Great Depression of the 1930s.

You could kiss goodbye to the commodities boom that we are now celebrating. In any pandemic, China - with its 1.2 billion population and meagre health resources - would be hard hit. Also, if the SARS episode is any guide, the pandemic could quickly entrench itself in the face of local government denial and secrecy.

Two Canadian analysts, Dr Sherry Cooper and Donald Coxe, who are with the Toronto-based BMO Financial Group have just published what they call “An Investor’s Guide to Avian Flu”. You might feel this a tad insensitive compared with the other issues involved, but the economic fallout from a crisis in confidence could well affect more people and linger longer than an actual pandemic, which could be bowled over in relatively short order by the development and distribution of a suitable flu vaccine.

There are a number of treatments already available, although they will take time to produce and are not in sufficient supply to deploy on any large scale. These include the Relenza antiviral drug developed by the Australian company Biota. The German government last week placed an order for 1.7 million packs of Relenza - greater sales than the drug had achieved in the previous five years.

Cooper and Coxe say in their report that should a pandemic occur, governments “would not hesitate to impose quarantining, including requiring people who may have had an exposure to the virus to stay within their homes, denying landing rights to planes and ships from countries where the disease is spreading, forcibly isolating people showing suspicious symptoms, banning concerts, parades and sporting events, and making business responsible for enforcing such emergency rules on their staffs.”

WHO believes that stock markets would close once a pandemic was confirmed. Cooper and Coxe reckon there would be a sequential response, with Asian markets closing first and North American and European markets staying open “until local business closures and soaring death rates precipitated panic”.

According to Cooper and Coxe, a runaway pandemic would hit commodity prices especially hard. The combination of collapsing demand from China and India and the likelihood of a collapse in demand for housing and cars in the OECD nations would mean that prices of base metals and steel would plunge, probably reversing their entire post-9/11 rally.

Oil prices would also plummet because of the ending of the economic booms in China and India and because of the sudden reduction in the number of consumers in the OECD.

There would, they say, be no rush into precious metals, if only because high global death rates would mean a large-scale estate liquidation of jewellery.

Lack of meaningful surge capacity in healthcare systems worldwide would also magnify the economic impact, because rates of both absenteeism and death would be sharply higher than should be the case.

Income and profitability of businesses of all kinds would suffer. Financial institutions would be under enormous pressure to sustain their services, due to employee absenteeism and chaotic financial markets. The insurance industry in particular would take a heavy hit.

Attendance at public events, such as theme parks and movies, would collapse - if not banned outright. Patronage of restaurants (particularly Asian-style), hotels and bars would plummet.

People would shun high-rise buildings not because of terrorism but because of nature’s microbial attack. Stockpiling of basic food, pharmaceuticals, water, energy and safety appliances would initially lead to shortages and skyrocketing prices.

Looking at the North American residential property scene, Cooper and Coxe claim that soaring death rates would puncture the housing bubble and create vast housing oversupply. Apartment owners would slash rates to try to replace deceased tenants. As prices of houses and apartments fell, the many millions who had bought their properties with little or no money down, would default, exacerbating the rate of price decline. The 1918 experience was that infection and death rates were much higher in the cities than in smaller centres.

But take heart. Unlike the 1918 catastrophe, investors will not simply have to depend on luck to protect the value of their portfolios.

Cooper and Coxe write: “Cash, put options on volatile stocks, high-quality bonds and high-quality dividend-paying stocks of companies with minimal exposure to the risks we have described, will be the best survival packs. They will provide the survivors of the pandemic with the capital to take advantage of the wide array of cheap assets that will - however temporarily - be available after the virus has joined its predecessors in whatever resting places the world has to offer.”

The Walsh family super fund owns Biota shares.