Will Covid-19 be a two-wave pandemic?

The pattern of reported and unreported Covid-19 deaths have peaked in the second wave at a height that is twice the height of the first wave (see graph below). The question that we must ask is whether we will see a third (or indeed a fourth and fifth) wave in South Africa.



From the very beginning of the Covid-19 pandemic, people have drawn parallels with previous pandemics, like the influenza outbreak of 1918 known as the Spanish flu.

The Spanish flu virus (H1N1) and SARS-CoCV-2 come from different viral families so there are limits to our learnings from the Spanish flu pandemic. However, the mode of transmission of both viruses are very similar. Both are spread primarily through respiratory droplets and in particular through the suspension of liquid droplets in the air.

The Spanish flu came in three waves. Although the virus never completely disappeared, people had developed a collective immunity after the third wave of infections. The graph below shows the relative strengths of the three waves of the Spanish flu as it was recorded for the United Kingdom.


With almost 50% of the South African population already infected and carrying a level of immunity to the virus, a third wave should be less severe than the second wave. What could impact on this outlook is the occurrence of a new variant of the SARS-CoV-2 virus that is more infectious than the 501Y.V2 variant that is prevalent in the second wave.

We should also consider the scenario where the SARS-CoV-2 virus reappears in wave after wave much like the seasonal flu does each winter. In this scenario, natural collective immunity would not develop against SARS-CoV-2 as it did for the Spanish flu. 

 

Comments

  1. NoopnrFebruary 5, 2021 at 9:20 AM

    In respect of your last point one would have to consider the extent to which susceptibility to new variants varies compared to existing ones. For example, if you survived a first infection (or were lucky enough to be asymptomatic) would you be more likely to survive second & subsequent variants assuming equal comorbidities. If so, the IFR could trend down.

    ReplyDelete
    Replies
    1. GaryIanFebruary 10, 2021 at 8:36 PM

      Good point. Even if individuals get reinfected they may be better equipped to deal with the viral attack

      Delete

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