SCIENCE is all about understanding the natural world. And a big part of that has always been understanding those bits of the natural world that threaten us, so we can protect ourselves.
While medical science has helped keep disease from the door, we haven鈥檛 licked it. For the past year, New 杏吧原创 has warned that an epidemic of bird flu in east Asian poultry could turn into the next great human plague. Twelve months on, you might expect that scientists would have worked out exactly what we鈥檙e up against and how we should protect ourselves. Yet surprisingly 鈥� and scarily 鈥� they haven鈥檛. It is surprising and scary because the stakes are so high.
The H5N1 bird flu virus has so far had trouble infecting people, but when it does it kills 75 per cent of them. The fear is that it could evolve to spread easily between people 鈥� and when flu viruses do that, they can infect a third of the people on the planet within months. The scary part is that, according to virologists, the virus could become that contagious and remain deadly at the same time.
Advertisement
Do the maths: a third of the people on the planet catch a virus that kills three-quarters of them. That鈥檚 1.5 billion people dead. This is the worst-case scenario that is keeping virologists awake at night.
But cheer up, it may never happen. Asia has an awful lot of H5N1 in its billions of birds, rubbing up against billions of people with their own flu viruses. Despite this, a pandemic strain has not yet evolved. Maybe H5N1 just doesn鈥檛 have what it takes 鈥� whatever that is.
A flu virus is a wonderfully simple thing 鈥� a mere 10 genes and a few proteins, and you have something that is as inescapable a part of human life as death and taxes. And yet we don鈥檛 know what subtle genetic change 鈥� it could be as little as one letter of RNA code 鈥� makes the difference between a people killer and a trivial infection in ducks. So we don鈥檛 know if H5N1 has the genetic constitution to pull off the worst-case scenario, or even what changes to watch for.
Understanding these issues is certainly part of the science we need to head off this threat. But more urgently, we need better epidemiology. In this week鈥檚 issue of The New England Journal of Medicine (vol 352, p 405), Klaus St枚hr of the World Health Organization outlines a few of the basics we still do not know. Which species play the biggest roles in keeping the virus going? How can we distinguish H5N1 faster and more accurately from other kinds of respiratory ailments? Without that information we will never know how widespread infection is. And how long can people be infected before they show symptoms? A virus that is contagious during its incubation period can be virtually unstoppable 鈥� just look at HIV.
鈥淒o the maths: a third of all people on Earth catch a virus that kills three-quarters. That鈥檚 1.5 billion dead鈥�
Epidemiology must also inform our plans for protecting ourselves if the pandemic virus does emerge. Plan A is to nip it in the bud. We watch carefully for the first cluster of human cases. Then we somehow confine everyone who has been exposed within a limited area and treat them aggressively with drugs and vaccination. If the virus gets out we watch for the brush fires and quench them. If this works, the virus is extinguished. Plan B is to protect everyone with a vaccine or drugs.
Right now governments do not seem to have understood that these are the only options on offer. And even in combination, they leave a lot to be desired. A few developed countries are laying in stocks of antiviral drugs. But these are in national stockpiles far from where the first cluster is likely to occur, and few governments have concrete plans for deploying them early to contain any outbreaks.
Plan B will in any event be impossible unless we have a vaccine and can make enough of it in time. Phase I trials of a putative vaccine are under way, but we do not have the manufacturing capacity to make it quickly enough for everyone to be vaccinated once a pandemic starts. Likewise, 鈥渄rugs for all鈥� will only work if the drugs are stored on a truly global scale and if we can make enough of them 鈥� which at present we cannot.
We may be lucky. There could be something about H5N1 that stops it becoming pandemic. But then there are its worrying cousins, H9 and H7. Science has taught us enough about flu to know one thing: a pandemic is overdue. Luck won鈥檛 last forever.
