Those of us trying to model the Covid-19 pandemic should try to be humble; there is more we don’t know than we do.
Anyone who claims to know what the infection or mortality rates are for this disease is either deluded or dishonest.
But, with time-tested scientific analysis, some things are predictable: on April 17, after three weeks of lockdown, the sun will rise in Cape Town at 7.10am, and we will still be at the start of a Covid-19 outbreak.
Though our current three-week lockdown will temporarily suppress transmission in the South African epidemic, it won’t eradicate it, and if we just go back to business as usual, we will have endured the lockdown for nothing.
Usually, viral outbreaks, like flu, peak and subside long before everyone gets infected.
The network for transmission becomes thinned, and transmission just can’t be sustained.
This thinning has many potential contributing factors: for most viral infections, people acquire substantial immunity from infection, so once they recover (sometimes quite quickly) they no longer contribute to the spread.
Of course, people may also adapt their behaviours if they see a severe outbreak around them — but even without changes in behaviour, there are natural reasons for epidemics to die out.
This pruning of the transmission tree, however, relies on a substantial fraction of people getting at least a brush with the infection — and it is from the study of seasonal flu and similar viruses that people have been circulating some alarming estimates of how many people might contract the new coronavirus.
Indeed, a scarily large number of people would need to be infected for there to be a collective “herd immunity” that would make any residual transmission dwindle away harmlessly.
Even in severe Covid-19 outbreaks like in Wuhan, only about 1% of the local population was ever infected before draconian measures pretty much shut down transmission.
While restrictions are now being eased, the population is almost as susceptible to a re-ignition of the epidemic as it ever was, and any reintroduction of infection to Wuhan would be just about as dangerous as the initial outbreak.
So the question is, what do we do after April 16?
This is a political, not a purely technical, question — though there are technical aspects to understanding what will be happening as we try to get out of a strict lockdown to something more sustainable.
I don’t think epidemiologists necessarily have the insights or creativity to come up with the answers, but we can suggest some of the important things we will have to consider and debate.
Between quasi-incarceration and going back to how things were, there is a wide spectrum of measures, and infinite scope for creativity.
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