DELEGATES from across the world will meet next week at the World 午夜福利1000集合 Organization in Geneva, Switzerland, to consider an irrevocable act: the deliberate and final extinction of a species.

Everyone agrees that the world is a better place without this particular species roaming free. There was universal celebration when it was all but wiped out more than three decades ago. Even so, the WHO debate stands a fair chance of stalling because the group is well practised in not quite making things happen where this species is concerned. It will be the sixth attempt to resolve this issue. So what鈥檚 going on?

The species is the Variola virus, which causes smallpox, and the group deciding its fate will be the 67th World 午夜福利1000集合 Assembly, the WHO鈥檚 decision-making body.

At its height, smallpox killed 1 person in 12 and mutilated hundreds of millions more. During the 20th century, vaccination steadily edged it towards extinction. Like most doctors of my generation, I never saw a case after qualifying in 1977 and hopefully never will, because the global eradication of smallpox was confirmed in 1980.

The disease may have disappeared globally but the virus is not extinct. After eradication, the WHO closed smallpox research labs across the world and destroyed all stocks of the virus except for two duplicate sets of representative strains, which were kept for research in two high-security establishments. This was in 1983, when US president Ronald Reagan鈥檚 Star Wars initiative dominated the headlines. In true cold war symmetry, the WHO handed one batch to the US Centers for Disease Control (CDC) in Atlanta, Georgia, and the other to the State Research Centre for Virology and Biotechnology in Koltsovo, Novosibirsk, then part of Soviet Russia. At both sites, the virus samples were locked away in liquid nitrogen. The WHO has repeatedly postponed the date of destruction because of US and Russian opposition.

Not much has changed since the last time the stockpiles were spared in 2011. Experimental smallpox drugs are in the pipeline. The intact virus is pretty redundant as a research tool: the genomes of many strains have been thoroughly sequenced and key proteins required by the functioning virus can be made in the lab. Over the last 30 years, the stocks of virus have contributed little to scientific understanding, other than confirming that new drugs aimed at other viruses still plaguing us are not much use against smallpox.

The Advisory Group of Independent Experts, convened by the WHO, recently argued that keeping the virus will never serve any useful purpose. It has been overruled by another expert committee, also convened by the WHO; the Advisory Committee on Variola Virus Research says the stockpile can help the work on antiviral treatments.

Talk of the need for new treatments is undoubtedly influenced by past misuse of the virus for military ends and contemporary fears that terrorists or a rogue state might commandeer smallpox as a bioweapon.

During the 1760s, the English hatched a plot to exterminate Native Americans by deliberately infecting them via blankets that had been exposed to smallpox. They didn鈥檛 wipe them out, but many died. This theme was picked up and refined 200 years later by the Russians. It is an unfortunate coincidence that their highly virulent strains of weapons-grade smallpox were developed at the VECTOR germ warfare laboratory in Koltsovo, on the same site that now houses the virus stock that was entrusted to the Soviet Union.

The Variola virus is a genie which must not be allowed to escape from its bottle into the world again. The chances of smallpox being released, inadvertently or deliberately, from either the CDC site or Koltsovo are vanishingly small, given the elaborate security.

鈥淭丑别 Variola virus is a genie which must not be allowed to escape from its bottle into the world again鈥�

However, that risk will never be zero while stocks remain. Destruction removes that risk and might allow the WHO to focus on what we will really need if smallpox ever comes back, either because a related virus evolves to replace it, or a human villain releases some unknown cache.

There is no proven treatment for smallpox and our vaccines, while effective, are in short supply. The vaccine issue is where we should focus our efforts. A handful of countries have enough to immunise just 20 per cent of their populations; the WHO used to hold hundreds of millions of doses but destroyed most when freezer space was in short supply during the 1990s. In an emergency, it would take months for vaccine production to get up to speed, and even then this would be on a pathetically small scale.

Today鈥檚 transport networks are capable of spreading the virus quickly through the biggest susceptible population in the history of our species. Immunity was lost as vaccination, which carries health risks, stopped soon after eradication. So a smallpox outbreak could easily become a global catastrophe, which the WHO鈥檚 stocks of Variola would do nothing to mitigate.

So what should happen in Geneva next week? Above all, the World 午夜福利1000集合 Assembly should vote to destroy the stocks of Variola virus without further delay. This would prevent yet another unedifying and expensive cycle of indecision. If the threat of smallpox staging a comeback is at all credible then our capacity to deal with it must also be credible.

Also, we must not forget the wider significance of smallpox. It is not just one of the nastier exhibits in the museum of medical horrors. It is the only human infection that we have successfully exterminated. It is time for the WHO to move on.

This article appeared in print under the headline 鈥淪mallpox must die鈥�

SYSTEMATIC searches over the past twenty or so years have shown that the
major planets orbit the Sun amid a vast number of minor bodies. That these minor
bodies occasionally hit the major planets is clear both from the cratered
surfaces of planetary bodies throughout the Solar System and from the 1994
impact of D/1993 F2鈥攂etter knows as Shoemaker-Levy 9鈥攚ith Jupiter.
There are many thousands of objects on orbits that will cross Earth鈥檚 path, so
it is not a question of if Earth will be hit: it is a question of when.

Books on the impact threat seem to be flavour of the month with publishers.
In Impact! Gerrit Verschuur attempts a coherent overview of this
threat. He begins with the emergence of the realisation that something big hit
the Earth 65 million years ago (contributing to the demise of the dinosaurs) and
that the impact occurred on the Yucat谩n peninsula in Mexico. The
following chapters offer a general introduction to the debris that litters the
Solar System. The book then delves more deeply into specifics of the impact
threat. Verschuur includes the now obligatory retelling of the comet-Jupiter
impacts of 1994, before dealing with current and future searches for potential
impactors and the possible mitigation of the threat.

He enjoys controversy, and rehearses the arguable idea that human history has
been moulded by impacts and that the similarity of disaster myths among widely
scattered cultures stems from real events. Chapter 11 deals with another
contentious topic, coherent catastrophism, which invokes disintegrating giant
comets as the source for periodic comet showers and enhanced impact rates.

Verschuur estimates the chances of the Earth being hit again, warning that an
asteroid landing in the sea would be more destructive than an impact on land
because it would generate huge tsunamis.

But there are problems. A brief mention of Jupiter Trojans is hardly
necessary, as these objects are not a threat to the Earth. Verschuur fails to
distinguish between objects that are currently in Earth-crossing orbits and
those that are in orbits that will become Earth-crossing in the distant future.
So the remarks on the dust jacket about the largest known near-Earth asteroids
(NEAs) are misleading as the orbits of these do not currently cross the orbit of
the Earth and present no immediate threat.

There is no real discussion, other than an offhand remark, on the procedures
by which NEA discoveries are followed up, reported and disseminated. This is a
serious omission as discovery without follow-up is worthless. The failure to
reobserve 1994 ES1 was an aberration. Since 1994, the Minor Planet Center (where
I work) has put its home page on the World Wide Web
(http://cfa-www.harvard.edu/cfa/ps/mpc.html) to assist in the immediate
follow-up of newly discovered NEAs. The recent close approach of 1996 JA1 was
handled successfully by the centre using its near-Earth orbit confirmation
page.

Numerous factual errors spoil the book. For example, the fifth minor planet
was not discovered until 1845. And the encounter distance of 1994 ES1 was 0.001
astronomical units, rather closer than the given value of 0.1 astronomical
units.

The fact that Verschuur is not a minor-body researcher is revealed in the
lack of fuller accounts of the rediscovery of Apollo in 1973 (showing that blind
luck is often an integral part of science) and the fiasco surrounding the first
comet discovery by the IRAS satellite, one that was resolved by the British
amateur astronomer George Alcock.

So Impact! is not the definitive book on the impact threat.
Verschuur is a fine writer with an engrossing writing style. Despite his obvious
skills of popularisation, the book is spoilt by its errors of fact. But a second
edition, correcting the errors, would be well worthwhile.