If lockdown cannot save lives, then don't destroy the economy

The latest NMG model for the COVID-19 pandemic in South Africa shows a best fit for the confirmed cases and reported deaths to 3 May 2020 that:
  • Uses a reproduction number of 1.86 for the speed at which the virus is spreading; and
  • Has 92% of infections going unreported
At this speed of transmission and extent of under reporting, it will be difficult to stop the virus infecting the majority of the population (according to the logic of a SEIR model that is).  What is important to consider is whether the COVID-19 deaths can be averted in the South African context.  If the spread of the virus cannot be contained at a level close to or below a reproduction number of 1.00, then the lives lost cannot be avoided but only delayed. If lockdown cannot save lives, then we should think carefully whether delaying the pandemic is worth the damage being done to the economy.

The latest NMG model can be found at https://nmg-covid-19.sctechnology.co.za/. The model projects a peak in infections by August 2020 and cumulative deaths from COVID-19 of some 176 000 before year end in South Africa.  A SEIR model for the pandemic was recently published by the Actuarial Society of South Africa.  This model shows a forecast of a much lower number of cumulative deaths of 48 300.  This just demonstrates how much projections from SEIR models can vary from one other.  Both numbers are scary, and I would argue that it is less about the size of the number of deaths forecast but rather about whether these deaths can be avoided.

The graph below compares the projected weekly COVID-19 deaths from the NMG model to the all-causes deaths:

South Africa is unusual in that the all-causes deaths have fallen below the 2019 levels due to the impact of early lockdown.  In most other countries, all-causes deaths have moved above prior year levels due to COVID-19.

It is not clear whether this trend will continue for South Africa during the winter months when the seasonal flu would typically cause an increase in deaths and before COVID-19 deaths start to impact on the all-causes numbers. 

One of the questions that we should be posing of our early lockdown experience is whether a generalised lockdown can halt this pandemic given the South Africa context.  If it cannot, as our modelling appears to demonstrate, then it is time to pivot to another strategy.
5 May 2020




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