In this post, we compare the focus of the COVID-19 literature published in the very early stages of the pandemic (up to March 23rd) to the focus of literature published during August 2020.

The first graph below is based on the literature based on the Corpus downloaded from PubMed 23rd March. The literature consisted of 1323 publications, of which there were 225 keywords that occurred in three or more manuscripts. These divided into four clusters, that are described in this preprint

The second graph below is based on COVID-19 literature published during August 2020. The literature consisted of 10901 publications, of which there were 1179 keywords that occurred in 5 or more manuscripts. The keywords divided into five main clusters. To create the map, we used the LinLog method. The minimum cluster size was set to 15. We provide a brief description of the clusters from the August COVID-19 litterature: Within cluster 1 (red), the “Pandemic of viral pneumonia; public health and world spread”, we found topics relating to “Public health concerns” “health personnel, education and behavior”,  “Guidelines and health care”, and “vulnerabilities in health care”. Cluster 2 (green), “Treatment of COVID-19”, include topics relating to “Epidemiology of virus transmission” “Antiviral agents and vaccines”, “Cancer and chemotherapy”, “Angiotensin and diabetes” and “Antibodies and passive immunization” Central themes in cluster 3 (blue), “Epidemiology of the pandemic and disease”, are “Respiratory illness and care”, “Risk factors and mortality”, “Clinical investigation and diagnosis” and “Population epidemiology”. Central themes in cluster 4 (yellow), “Surveys of disease and mental health”, are topics relating to “Population surveys and anxieties” and “Health care and migration”. Cluster 5 (purple), is dominated by one single theme, namely topics relating to “Lab-work and diagnostics”; which is also what we labeled this cluster.

When inspecting and comparing the network graphs illustrating the COVID-19 literature published during August and one published during the early phase (January 1st – March 23rd, 2020), we notice some consistent themes, and some emerging themes. Much of what was being covered during the early phase is still in focus. For instance, the topics from the “health and pandemic management” cluster from the early phase is reflected in the topics covered in the “Pandemic of viral pneumonia; public health and world spread” cluster in the August literature network graph. Early in the pandemic, there was not however, a focus on mental health issues. This has become an additional focus later in the pandemic, and is evident in the “Surveys of disease and mental health” in the August literature network graph. These are just some examples of insights that can be gained from comparing network graphs from different time periods.

Figure 1: The research focus in the very early Covid-19 literature

Figure 1 Notes: Red cluster: Health and pandemic management; Green cluster: The disease and its pathophysiology; Blue cluster: Clinical epidemiology of the disease; Yellow cluster: Treatment of the disease.

Figure 2 (below): The research focus in a later stage of the Covid-19 literature

Figure 2 notes: Red cluster: Pandemic of viral pneumonia; public health and world spread; Green cluster: Treatment of COVID-19; Blue cluster: Epidemiology of the pandemic and disease; Yellow cluster: Surveys of disease and mental health; Purple cluster: Lab-work and diagnostics.

Tables of most central keywords in each cluster; in literature published during the early phase of the pandemic, and literature published during August.

The tables below provide an overview of the most central keywords in each cluster in the two time-periods. We extracted more keywords from the second time period as there was substantially more literature published in August alone, than the first 12 weeks of 2020, which the first map is based on. (Centrality measure used is weighted degree centrality)

Table 1: Most frequent keywords in the very early Covid-19 literature

Health and pandemic management
The disease and its pathophysiology
Clinical epidemiology of the disease
Treatment of the disease
coronavirus infection pneumonia female sars
viral pneumonia outbreak adult animals
betacoronavirus epidemiology male genome, viral
china antiviral agents middle aged phylogeny
disease outbreaks viruses aged zoonosis
travel republic of korea young adult wuhan
pandemic lopinavir fever chiroptera
global health transmission tomography, x-ray computed communicable diseases, emerging
infection control ritonavir children disease reservoirs
public health mortality lung peptidyl-dipeptidase a

Table 2 (below):
Most frequent keywords in a later stage of the Covid-19 literature

Pandemic of viral pneumonia; public health and world spread (Red) Treatment of COVID-19 (Green) Epidemiology of the pandemic and disease (Blue) Surveys of disease and mental health (Yellow) Lab-work and diagnostics (Purple)
pandemic antiviral agents female surveys and questionnaires clinical laboratory techniques
coronavirus infection animals male cross-sectional studies rna, viral
viral pneumonia sars middle aged anxiety real time polymerase chain reaction
betacoronavirus inflammation adult health personnel antibodies, viral
public health peptidyl-dipeptidase a aged mental health sensitivity and specificity
united states spike glycoprotein, coronavirus young adult pregnancy reverse transcriptase polymerase chain reaction
quarantine epidemiology adolescent depression reproducibility of results
infection control cytokines aged, 80 and over prevalence immunoglobulin g
italy hydroxychloroquine retrospective studies exercise diagnosis
telemedicine viral vaccines children stress, psychological serological test
disease outbreaks antibodies, monoclonal china pregnancy complications, infectious polymerase chain reaction
communicable disease control ace2 risk factor health knowledge, attitudes, practice seroepidemiologic studies
delivery of health care interleukin-6 severity of illness index adaptation, psychological asymptomatic infections
global health infection treatment outcome risk immunoglobulin m
personal protective equipment vaccine comorbidity stress molecular diagnostic techniques
infectious diseases viruses hospitalization nurses asymptomatic diseases
health policy cytokine release syndrome child, preschool attitude of health personnel specimen handling
social isolation host-pathogen interactions tomography, x-ray computed health behavior family characteristics
united kingdom protein binding infant fear olfaction disorders
practice guidelines as topic molecular docking simulation risk assessment students nasopharynx

To open the maps directly in VOSviewer, please use the relevant MAP and NET files (Co-occurrence files from March 23rd and the files for August2020Total, available through the Open Science Foundation (OSF) repository: