Introduction

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Figure 2. March to May 2021: possible scenarios for national epidemics. Blue: new SARSCoV-2 infections due to old variants; red: new SARS-CoV-2 infections due to new variants. On the left, mitigation measures succeed in keeping case numbers low until the general availability of vaccines for the adult population. On the left, an uncontrolled epidemic is fuelled by the higher transmissibility of the new SARS-CoV-2 variants. Graphic copyright: Süddeutsche Zeitung, 5 February (Berndt 2021).

With viruses, some mutations emerge while others recede. Rarely does one or more mutations confer a “selective advantage” to a new variant, for example enhanced transmissibility. When it does happen, such variants can then become the new dominant virus.

Over the last two months, several new SARS-CoV-2 variants have been described that are more transmissible, may escape both natural and vaccineinduced immunity and could impact COVID-19 morbidity and mortality. It is too early to assert that these variants will create a new pandemic within the pandemic, however, in countries like England, South Africa, Brazil, Ireland, Portugal and Israel, they may have modified the dynamic of the latest outbreaks for the worse. More transmissible SARS-CoV-2 variants will replace older variants – everywhere! Countries where the prevalence of these new variants is still low should anticipate rapid spread within the next weeks and months and plan ahead accordingly, ie closing/restricting borders, etc. The current trio infernale: • B.1.1.7 (first described in England; Rambaut 2020) • B.1.351 (first described in South Africa; Tegally 2020) • P.1 (first described in Brazil; Faria 2021)