SARS-CoV-2 coronavirus and COVID-19 disease: a pandemic story update

It is now just over two years since the World Health Organization (WHO) declared that the spread of COVID-19 met the criteria for a pandemic.¹ Previous reviews^2,3 have considered the characteristics of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; Fig 1), the clinical disease COVID-19 and approaches to testing. This article will consider the effect of variants and vaccination on the epidemiology of this infectious disease. It will also discuss the role of laboratory testing in detecting this virus and tracking variants. There are now effective vaccines and antiviral treatments, and these will be reviewed.

                At the end of March 2022, there had been over 470 million confirmed cases of SARS-CoV-2 worldwide.⁴ This figure is likely to be an underestimate, due to disparity in testing across the world. Similarly, while official reports indicated that around six million people had died during the first two years of the pandemic, a recent estimate based on excess death data suggests the true figure was closer to 18 million.⁵ Based on available data, the case fatality rate (CFR) for COVID-19 appears to be 2–4%.⁶ Two previous novel coronaviruses emerged in the 21st century, namely severe acute respiratory coronavirus (SARS-CoV) and Middle Eastern respiratory syndrome coronavirus (MERS-CoV).² As Table 1 shows, compared to these viruses, SARS-CoV-2 has already infected many more people and been responsible for more deaths, despite the lower CFR. During the 2009–10 ‘Swine ‘flu’ pandemic, at least 700,000 people were infected. The number of confirmed deaths reported to the WHO was 18,631,⁷ but modelling of excess deaths suggested the actual number was much higher, although it was still similar to the rate observed for seasonal influenza.

Virology