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Since December, 2019, coronavirus disease 2019 (COVID-19) has affected more than 100 000 patients globally.1 COVID-19 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has a case-fatality rate of 2·3%, with higher rates among elderly patients and patients with comorbidities.2 Person-to-person transmission is efficient, with multiple clusters reported. Clinically, patients with COVID-19 present with respiratory symptoms, which is very similar to the presentation of other respiratory virus infections. Radiologically, COVID-19 is characterised by multifocal ground-glass opacities, even for patients with mild disease.3

Knowledge of virus dynamics and host response are essential for formulating strategies for antiviral treatment, vaccination, and epidemiological control of COVID-19. However, a systematic study on these aspects has not been done. In The Lancet Infectious Diseases, Kelvin To and colleagues4 report the viral load and antibody profiles of a cohort of 23 patients admitted to hospital with COVID-19. In these patients, the viral load peaked during the first week of illness then gradually declined over the second week. Viral load was also shown to correlate with age. Furthermore, both IgG and IgM antibodies started to increase on around day 10 after symptom onset, and most patients had seroconversion within the first 3 weeks. Finally, the IgG and IgM antibody level against the SARS-CoV-2 internal nucleoprotein and the surface spike receptor binding domain correlated with neutralising activity.

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30235-8/fulltext