Like the great majority of the quickkiller infectious diseases that have emerged to ravage the human race, the influenza virus probably originated in animals that have always lived in relatively dense populations — waterfowl, in this case — and only colonized human beings after we started living in societies millions strong. Clusters of pre-civilized humans, living in tiny and relatively isolated hunter-gatherer groups, would not have been a suitable environment for highly infectious diseases since they would soon have run out of hosts and died out themselves. But you can always trust a virus to spot a new opportunity: the best estimate is that the lethal A strain of the influenza virus first moved from waterfowl to people about 2,500 years ago, probably via domesticated chickens that picked up the virus from wild ducks but were living practically under the same roof as their human owners.
Evidence is accumulating that all the A strains of human influenza originated in birds. Over time, many of these A strains have adapted to their new human environment and become less lethal only because human immune responses have improved. But new strains keep hopping across the species barrier, and some of them are killers when they first arrive. Three times in the eighteenth century, four times in the nineteenth, and three times in the twentieth century, an especially virulent new A strain of the influenza virus has caused millions of deaths.
The first deaths from direct bird-tohuman transmission of the h5n1 virus happened in Hong Kong in 1997, and the authorities responded by killing all 1.4 million domestic fowl in the city’s markets and surrounding countryside. But the virus keeps hopping into human beings — about 130 cases by the end of November 2005, according to the who; of those sixty-eight have died, mostly in Vietnam, but also in Thailand, Cambodia, and now in Indonesia and China.
All flu viruses mutate rapidly in order to get past the immune systems of their target species. That’s why you need to be vaccinated every year to have some protection against recent variants. In fact, human-adapted flu viruses mutate so fast that the vaccines are rarely fully effective against the most recent mutations, which is why a wave of flu travels around the world every winter, usually infecting up to 15 percent of the world’s people. Most suffer only a few days’ discomfort, but even in normal years significant numbers of people, mostly the very young and the very old, die of complications from the disease: roughly 1,000 a year in Canada.
Pandemic planning in Canada began in 1983, but the sars outbreak in Toronto in 2003 gave everybody an added sense of urgency. Establishing itself as a leader in the field, in February 2004 Canada released a comprehensive Pandemic Influenza Plan. “[Avian flu] is the most important threat currently to global health that we know of,” explained Dr. Frank Plummer, scientific director general of the National Microbiology Laboratory.
Plummer’s lab takes up most of the Canadian Science Centre for Human and Animal Health, a sleek new building that looks rather out of place in the nondescript north Winnipeg neighbourhood it calls home. You expect the stringent security measures, the Biosafety Level-4 containment lab and the researchers dressed in something closely resembling spacesuits, but the real surprise is the Emergency Operation Centre. It looks like an upmarket, miniaturized version of the famous norad command centre under Cheyenne Mountain in Colorado Springs, full of computer screens and windows that blank out when the proceedings inside must remain secret even from others in the building. It is from this room, together with a similar facility in Ottawa, that the war against a pandemic would be directed in Canada.
If the h5n1 virus becomes easily transmissible between people, it will probably happen first in China or Southeast Asia, where several hundred million rural families live in close proximity to their chickens, ducks, and pigs. Their domestic fowl are frequently exposed to the feces of the wild birds that are the main reservoir of the virus, and epidemics of avian influenza of increasing virulence have been hitting these domestic birds for the past eight years. In various attempts to contain the outbreaks, over 150 million birds have been killed. If the h5n1 virus does succeed in making the transition to a humantransmissible form, however, it would travel by air, as sars did, and arrive before Canada could close its borders. (It has no current plans to do so.) “By the time we did it, it would be here anyway,” explained Dr. Paul Gully, deputy chief public health officer of the Public Health Agency of Canada.
We are somewhat better equipped to deal with some of the side effects of a major flu pandemic these days than they were in 1918. We have antibiotics to deal with pneumonia and other bacterial infections that strike flu patients and ventilators to help them breathe while their lungs are being overwhelmed. But there is very little “surge” capacity in Canada’s healthcare system (or anybody else’s). When twenty times as many people as usual are stricken with life-threatening infections, we cannot suddenly come up with twenty times as many hospital beds, twenty times as many ventilators, twenty times as many doctors and nurses. Not to mention the fact that health-care workers are just as vulnerable to the virus or may be at home looking after sick family members.
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