Full spectrum of COVID-19 severity still being depicted

Chaolin Huang and colleagues¹ first reported the clinical features of patients infected with severe acute respiratory syndrome corona virus 2 (SARS-CoV-2; previously known as 2019-nCoV), which emerged in Wuhan, China. Their study will contribute to the diagnosis and treatment of 2019 novel coronavirus disease (COVID-19). Meanwhile, the conclusions have caused a certain degree of social panic.

Huang and colleagues¹ only included 59 suspected cases with fever and dry cough, and 41 patients were confirmed to be infected with SARS-CoV-2. They concluded that SARS-CoV-2 infection was associated with a high rate of admission to intensive care units (13 [32%] of 41 patients) and mortality (six [15%] of 41 patients); however, we believe these conclusions were inaccurate and misleading.

Case fatality ratio should not be confused with mortality rate. Case fatality rate is defined as the proportion of people who die of a certain disease; however, mortality rate usually reflects the death rate in an entire population.² The case fatality rate is therefore approximately 15% in the study population,¹ but this estimate is also inaccurate since case detection is highly biased towards the more severe cases in the early stages.³ In fact, a large number of mild and asymptomatic patients might not receive timely diagnosis or health care, which can conceal the real incidence and allow disease progression.

Patients with SARS-CoV-2 infection are presenting with a wide range of symptoms. Most patients seem to have mild disease, and about 20% appear to progress to severe disease, including pneumonia, respiratory failure, and, in some cases, even death.⁴ As of Feb 12, 2020, WHO⁴ reports that 45 171 people have been diagnosed with SARS-CoV-2 worldwide, and 44 730 of these cases are in China.⁴ Of the confirmed cases in China, 8204 (18%) cases were recorded as severe infections, and 1114 (2%) patients died, which is a lower case fatality rate than previously reported.4, 5 The case fatality rate for COVID-19 reported by Huang and colleagues¹ could be misunderstood, and detection bias should not be neglected.