There is a cure without a vaccine – and that’s to ensure the coronavirus is left with no place to go
How do you kill a virus? How do you eliminate a minuscule genetic strip of instructions whose purpose is to replicate itself? On our skin, of course, soap is highly effective. It works by washing its way through the layer of fat that encases coronaviruses so that, as Dr Charlotte Houldcroft, at Cambridge university, vividly puts it, “the genetic guts of the virus spill out”.
Inside of us, the task is harder, so we wait for drugs and vaccines.
But there is another way – an endgame for coronaviruses, even without treatments and vaccines.
Already this century, outbreaks of deadly cousins of today’s virus have twice been crushed without global immunisation programmes. So will it be third time lucky?
“There’s no reason for a second wave,” says David Heymann, professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine. Few are better placed to know. In a long career at the WHO, he headed the global response to Sars, the disease that emerged in 2002 from another coronavirus (Sars-cov-1), so close to today’s that the current pest is named after it.
In 2002, also, the virus made the species jump at a Chinese market – in November or December. Then, too, it looked grim. “It spread quite easily,” says Heymann. And whereas the IFR – infection fatality rate – for Covid-19 is thought to be under 1, Sars killed one in 10 who caught it. But a little more than six months after it emerged, Sars was eliminated. The last cases, excluding accidental release from labs, came in July 2003.
Now, says Heymann, we are once again at the six-month mark. “It will be important to take stock in July.”
There are three fates for any new virus that crosses the species. The first is a dead end: like rabies, it will infect one person and go no further. The second awaits those that cause outbreaks but can be ushered back whence they came – like Ebola.
The third is where the disease cannot be eradicated and becomes, instead, endemic. Think HIV.
“We don’t yet know its destiny,” says Heymann. “It could become endemic in humans. It could mutate in such a way it becomes more or less virulent. Or more or less transmissible. Or it could disappear.” Sars, following its emergence in July, disappeared.
That, it is important to note, did not happen on its own. Rather it was the result of the first global public health response which, thanks to modern communications, unfolded in real time. There were travel bans, tracing, and cooperation across borders.
This time, says Heymann, such co-ordination has hit problems. “The world is working together at technical and scientific levels, but not so well at the political level.”
Sars infected around 8,000 people, with 774 deaths. At the WHO this was considered a narrow escape. In the event, Sars-cov-1 proved something of an ally in the effort to corner it – causing people to spread the disease only when they were very sick. Many infections occurred in hospitals. As a result, tracing was far easier than today.
There is another factor. A great unknown. Many viruses become less virulent in a process known as “attenuation”. It happens to flu viruses, and others that jump the species barrier to humans. “Often,” Heymann says, “viruses cause less serious illness with passage through humans, we assume through mutation.” Sars-cov-2 might simply fade away.
Mutation is certainly occurring. At Cambridge, Houldcroft is part of a team that tracks genetic mistakes that may occur as the virus replicates. Most mutations are trivial but some become different strains that may be more, or less, dangerous than the original. A paper by Manuel Becerra-flores and Timothy Cardozo at New York University, for example, suggests European patients may have a slightly deadlier strain than that of Asians, and these may have seeded outbreaks on the east and west coasts of the US respectively – perhaps explaining the higher toll in US cities on the Atlantic than those on the Pacific.
Genetic tracking ultimately proved that Mers, the century’s other coronavirus (IFR: more than one in three), that emerged in Saudi Arabia in 2012, could not cause a pandemic. Once it had jumped from camel to human, it struggled to infect other people. “The transmission chains died out,” said the virologist Dr Gytis Dudas. “Humans were a dead-end host.”
But humans are clearly not a dead-end host today. So how, short of a vaccine, might Sars-cov-2 meet its end? In all probability, the only way will be to starve it of new hosts in which to replicate.
The UK has a long way to go. New cases are running at under 2,000 per day but the Office for National Statistics suggests the true number is about 8,000. In China (eight new cases per day) and South Korea (46) the picture, if we accept official figures, is very different; and in Taiwan and Vietnam it appears to have almost vanished.
What unites these countries is that they were the worst afflicted by Sars. “The Asian countries that responded to Sars and Mers were rapidly on top of this,” says Heymann. “They began to contact trace, isolate and control the outbreak, using [those tactics] instead of lockdown, based on epidemiology.”
Contact tracing and social distancing, he says, are the critical circuit breakers.
No need to sing about the latter measure: choirs in crowded rooms with spit flying about are this virus’s ideal habitat. One group in the US suffered an 87 per cent infection rate after a rehearsal in March.
Sars hit Canada in 2003, with 43 deaths. Yet today, it suffers 800 new infections a day. According to The Lancet, improvements were made to the country’s health system after 2003, but not the system of tracking, as demanded by a post-sars inquiry.
Sars ended not by some miracle, says Heymann, but because affected countries followed a time-consuming playbook: “Identifying cases, isolating them and then contact tracing, making sure that the contacts self-quarantined if they became sick, and were tested.”
Many countries show it is possible, without lockdown but with tracing, to get from where we are now to near extinction of the virus in under three months – without a vaccine.
If that were to happen, not just in the UK but everywhere, Sars-cov-2 would find itself with few places to go.
‘The world is working together at technical and scientific levels, but not so well at the political level’
‘The Asian countries that responded to Sars and Mers were rapidly on top of this. They began to contact trace, isolate and control the outbreak’