The Killer Plague is one of Hollywood's favourite apocalypses, a stalwart alongside thermonuclear war, asteroid impact and alien invasion. For decades, science fiction writers have had morbid fun contemplating what would happen if a mutant virus emerged from some shadowy corner of the world to spread around the planet: the collapse of civilisation, the abandonment of cities, bodies piling up in the streets and the end of life as we know it.
The latest addition to the genre is Contagion, directed by Steven Soderbergh and starring (briefly) Gwyneth Paltrow as an American businesswoman and "patient zero", who falls ill after a trip to Hong Kong. As the virus spreads, killing first dozens, then thousands, then millions, scientists led by Dr Erin Mears (Kate Winslet) try desperately to sequence its genetic code and produce a vaccine. What is striking about this latest attempt to portray microbial doomsday is that it is 100 per cent scientifically plausible.
Up to now, the film world has given us the unlikely "Rage" virus (28 Days Later); the emergence of an ebola-like organism (Outbreak) that causes victims to bleed to death; and a microbe that kills almost everyone and turns survivors into flesh-eating zombies (I Am Legend). But while these films played fast and loose with the truth in the name of plot and carnage, Contagion plays it straight, according to John Oxford, professor of Virology at Queen Mary, University of London and a world authority on epidemics. "I've seen it, and it's a cracking film," he says. "It shows my world."
Another expert, Dr Ian Lipkin, professor of Epidemiology at Columbia University in New York, was a technical adviser on the film. Having discovered more than 400 viruses and worked closely with the World Health Organisation after the 2002-03 outbreak of severe acute respiratory syndrome (Sars) in the Far East, he was able to tell the filmmakers what would happen if a new deadly flu strain were to emerge. For a start, Contagion lingers on shots of hands. While many people assume coughing and sneezing are the way in which viruses are transmitted, experts know that the greatest risk comes from objects that people have touched — door knobs, handrails, lift buttons and so on. It is probably more important to wash your hands constantly than to wear a mask. Then there is the virus itself. The deadly influenza strains, which sweep periodically round the world, are "zoonoses", viruses that emerge typically in chickens or wild birds and which swap genetic information with human influenza viruses when exposed to them. It is the ease with which the influenza virus is able to mutate and to swap genes, even within the body of a single host, that has meant that, to date, there is no generic vaccine that will work against all strains. When a new strain emerges, it typically takes several weeks or even months to develop a viable vaccine.
Two recent outbreaks — the 2009 H1N1, which originated in Mexico (and is expected to be in circulation again this winter), and the H5N1 "bird" or avian flu, which emerged in several locations in the middle of the past decade — did not turn out to be global killers, despite the hype at the time. In the case of H1N1, although the virus was highly transmissible and millions were infected, the mortality rate was low, probably less than 1 per cent. Bird flu was much more virulent, killing about half of the people infected. To date, the virus H5N1 has not mutated into a form that can be transmitted from person to person — direct contact with birds is necessary for infection.
Although the number of outbreaks has fallen since its peak in 2006, the United Nations recently warned of a possible global resurgence. The nightmare scenario is a strain that combines the virulence of H5N1 with the transmittability of H1N1. Such a "doomsday" strain did emerge 93 years ago, a variety of H1N1 that swept across the globe. The 1918 "Spanish" flu epidemic (which had nothing to do with Spain and may have been brought by migrating birds to First World War field hospitals in Picardy) killed between 50 million and 100 million people, about 4 to 7 per cent of the world population, and many more than were killed in the Great War. The mortality rate was between 5 and 7 per cent, and the virus was easily transmissible (in Contagion, the mortality rate is a nightmarish but, according to Oxford, "plausible" 30 per cent).
If a virus such as this were to emerge today, what would happen? On the positive side, we know a great deal more about viruses and have access to the technology to help contain them. A vaccine would be developed eventually and antiviral drugs would be distributed, doubtless saving many lives. In the 1918 outbreak, millions died from secondary bacterial infections, which we now treat with antibiotics. But, in many ways, we would be in an even worse position to deal with such an epidemic. Back then, few people moved much beyond their local communities and intercontinental travel took weeks. Today a million humans are in the air at any given time and an aggressive, transmissible influenza (with an incubation period typically of a few days) could be on every continent within 36 hours. Our cities are far bigger, and tens of millions more people live in proximity to each other than in 1918, maximising the ability of the infection to spread.
The Achilles' heel of modern society is its complexity. It is easy to imagine the mass panic if something such as the "Spanish" flu strain were to emerge. Power-station workers, delivery drivers and fuel-depot managers would either be sick or dead. The lights would go out, the shops would empty and the cities would grind to a halt; law and order would probably break down — something not seen in 1918.
Some people have accused the virologists of crying wolf. After the 2009 H1N1 outbreak, one commentator said we had become "demented", in thrall to the "scaremongering" scientists. These outbreaks always fizzle out, he said; few people die. But the only reason we have not seen a rerun of the 1918 outbreak is that, at any one time, some 30,000 doctors and scientists around the world are engaged in a massive international exercise in monitoring and watching, testing, swabbing, gene-sequencing and cultivating. We know our enemy and we are on its case, but unfortunately, in genetic terms, our enemy knows us.
