Future pandemics as bad as Covid are ‘a certainty’, says Sir Chris Whitty. He is right in one sense. So many people gained so much money, power or fame out of the pandemic that they will be all too willing to declare another one soon. The WHO is trying to vastly increase its budget and its powers on the back of Covid.
But if he means that we face more outbreaks of new infectious diseases that go global, then no, Whitty is wrong. The chances of another new virus spreading through the human race at a terrifying rate, burning through every barrier we erect – lockdowns, school closures, social distancing, vaccines – as happened in 2020, are small. The enthusiasm with which epidemiologists have tried to scare us about monkey pox and bird flu are cases in point: they are very nasty diseases but are unlikely to go global if we are careful.
There is one special exception: if the virus has been ‘trained’ in the lab to infect human cells.
That is why it is so vital to understand whether the Covid pandemic began as a lab leak or as a natural spillover from a mammal in a market. The evidence points strongly to a lab accident, Wuhan being the only city in the world where exactly the right kind of experiments were being done on exactly the right kind of bat virus. We now know that infected animals did not turn up in its markets.
The Covid pandemic therefore almost certainly reinforces a simple and (partly) reassuring lesson: natural spillovers of novel animal viruses are rarely infectious enough to start pandemics. When an animal virus first infects human beings naturally, it is often extremely virulent, with a high fatality rate, but not very infectious. Ebola, Nipah, Hendra, Marburg, Lassa, Hanta, Mers, Sars and bird flu all show this pattern. They kill a horrifying percentage of their victims, but struggle to sustain a spreading epidemic.
So they break out again and again, jumping from bats, rodents or birds, via pigs, civets or horses, kill a relatively small number of people and then die down as soon as doctors and nurses get a chance to isolate and treat victims. Exactly this keeps happening with bird flu at the present. Of course, eventually, the viruses would get lucky and find a way to sustain a global pandemic, but for that they probably need one of these slow-burn smouldering outbreaks to go untreated for months or years.
That must have been what happened with measles, smallpox and many other initially zoonotic diseases in the distant past: they eventually evolved a good fit to the receptors on human cells. Today we can usually diagnose and intervene quickly, before that happens.
In the early months of 2020 I thought this would happen to Covid too. Like its close cousin Sars in 2003-4, Covid-19 would be relatively easy to stop. I was wrong, and it puzzled me. How come this virus was so highly infectious – and not very lethal – from the very start? An analysis of its genes by my colleague Alina Chan showed that it had not experienced nearly as much mutation and selection in the early weeks as Sars. As Professor Edward Holmes of Sydney University put it: ‘Seems to have been pre-adapted for human spread since the get go.’
Er, how did it achieve that in a bat? Sarbecoviruses cause gut disease in bats, but respiratory disease in human beings. That adjustment requires a lot of evolutionary experimentation by the virus. We now know that the Wuhan Institute of Virology did experiments that increased the infectivity of sarbecoviruses ten-thousand-fold in ‘humanised’ mice – with human genes in their lungs. And that they planned an experiment to put a furin cleavage site into such a virus for the first time, enabling the virus to infect other kinds of cells. This virus is the only sarbecovirus with such a feature.
The lesson, therefore, of the Covid pandemic is that the risk of a natural outbreak going global is probably much smaller than the risk of a lab-leak outbreak going global. And here is the greatest irony of all. If Covid began with a lab leak, it was not just caused by virology research: it was caused by virology research that was specifically intended to predict and prevent pandemics. Even if this time it was just a horrible coincidence, they were looking for a gas leak with a lighted match, as one scientist put it.
Before the pandemic, the WHO and virus hunters like Peter Daszak of the EcoHealth Alliance, which funded the Wuhan work with US taxpayers’ money, were keen to point out the risk of lab leaks when pitching for funds. To avoid drawing attention to their own potential culpability, virologists now prefer not to discuss the topic.
‘Threat from lab enhanced viruses is increasing’ said one of Daszak’s fund-raising slides 2017. ‘The risk of [Sars] re-emergence from a laboratory source is thought to be potentially greater [than from a natural source],’ wrote the WHO in 2006. We went 101 years without a severe respiratory pandemic after 1918, and broke that run only once we started doing crazily risky experiments on viruses under the misguided impression that this way we could prevent pandemics.
But surely human interactions with nature are increasing, and the chances of picking up viruses is therefore growing because of things like deforestation? No. Southern China is reforesting rapidly, not deforesting, as rural peasants migrate to the cities to work in factories and eat food bought from supermarkets, not hunted in the jungle.
The same is true throughout much of the world. Intimate contact with wild animals is on the decline, thanks to economic development and urbanisation. Rural populations are now shrinking for the first time. The more that Africans can afford to buy frozen chicken rather than hunt ‘bushmeat’ the better. And peak human exposure to bat droppings probably occurred thousands of years ago when many of our ancestors were, literally, ‘cavemen’.