Characteristics of publications
There were 25,835 publications on coronaviruses, with 23,058 in only the SCIE (89.25%) 1,111 in only the SSCI (4.30%), and 1,666 publications in both (6.45%). The growth trend in publications on coronavirus in SCIE only coincided with that of all publications on coronaviruses from 1991-2020. The publications in SCIE increased slowly before the outbreak of SARS in 2003, with an average of approximately 134 publications per year. The number of publications in the SCIE clearly increased after the SARS outbreak, reaching a peak (1,089 publications) in 2004, and also rose slowly after the outbreak of MERS in 2012, with a peak (734) in 2016. Unlike the peak during the SARS outbreak, the peak during the MERS outbreak was lower and came later. The number of publications in the SCIE increased dramatically after the COVID-19 outbreak, with 10,221 publications in 2020, which was an unprecedented surge in research. Moreover, the publications in the SSCI and those that were in both the SCIE and SSCI rose slightly from 2003 to 2019 and clearly increased in 2020 (Fig. 1).
Our results indicate that publications in the SCIE played a dominant role in the field of coronavirus infection research. The outbreaks apparently stimulated research; however, the responses in research during and after the three epidemics were different, and the research field became diversified. Compared with SARS and MERS, COVID-19 generated a more dramatic and prolonged upsurge in publications. In May and June 2020, the volume of studies increased sharply, with studies mainly originating from areas affected by the epidemic (such as China, the United States of America [USA], Italy and the UK).