The Novel Coronavirus (April Edition)

The review was prepared by Liana Pankratova, Polina Rogacheva, Alla Loseva

2020 is characterized by the outbreak of a new virus that spread around the world with high speed and caused restrictive actions in all spheres of life. The virus started spreading in December 2019 in Wuhan (Hubei province, China), and soon researchers pointed at the emergence of novel coronavirus 2019-nCov. It then was confirmed in other countries and renamed as SARS-CoV-2, since it causes severe acute respiratory syndrome (SARS) and is related, though not identical, to the previous virus causing this syndrome (SARS-CoV). This post will discuss the scientific papers that have been published recently on the topic of the novel coronavirus SARS-CoV-2 and the disease COVID-19 caused by it.

For the review, we have twice performed a systematic search in the scientific literature database Scopus: as of March 27, and as of April 21. We then have built a map of publications based on their reference lists (Figures 1 and 2). Proximity in these maps and belonging to the same cluster mean that the papers cite the same publications, therefore the papers are likely to consider similar issues. The maps are built using VOSviewer software. 

The map based on March 27 data (Figure 1) is split into three clusters, roughly corresponding to the following topics:

• navy, upper left: epidemiology,
• yellow, right: virology and genetics,
• purple, bottom left: clinical characteristics, transmission routes, pathology.

The map based on April 21 data (Figure 2) is more detailed and reflects the research topics currently gaining popularity. The corresponding clusters are:

• yellow, right: virology, molecular biology, clinical medicine,
• blue, bottom right: modeling the epidemic spread,
• light blue, bottom center: mental health during the epidemic,
• brown, bottom left: epidemiology, public health research, including containment measures research,
• navy, upper left: pathology and comorbid diseases research,
• green, center: drug repurposing research,
• purple, center: radiology; obstetrics,
• gray, center and upper left: various topics.

Cluster description

Here we describe the most notable works from both maps, as well as the publications from the second map that have recently gained recognition. Clusters are presented according to the second map.

Yellow cluster: virology, molecular biology, clinical medicine

The upper part of the cluster contains papers on virology and genetics. Among them are the first clinical data on the virus transmission by the infected (Chan et al. 2020), papers on the genetic similarity of SARS-CoV-2 and bat coronaviruses (Ji et al. 2020; Zhou et al. 2020), on virus targets and the possibilities of blocking its binding to human cells (Hoffmann et al. 2020; Wan et al. 2020).

In the lower part of the cluster, there are papers on the clinical characteristics of the new coronavirus. The earlier research was made on Chinese data (Chen et al. 2020; Huang et al. 2020), then analyses on the American data appear (Holshue et al. 2020) as well as systematic reviews (Rodriguez-Morales et al. 2020). As they are the pioneering studies, they are also the most cited ones in the map – given that the article by Wang et al. (2020) from the light blue cluster belongs to the yellow cluster by its topic, as it is one of the first studies published in February on the clinical characteristics of the Chinese patients.

Blue cluster: modeling the epidemic spread

The most notable publication in this cluster is an early forecast of the outbreak spread in China and the health risks for other countries (Wu, Leung, and Leung 2020), for African countries in particular (Gilbert et al. 2020).

Light blue cluster: mental health during the epidemic

A handful of relevant articles is located in the lower part of the cluster. They discuss the measures of mental health that have been organized in China (e.g., Banerjee 2020; Xiang et al. 2020), including the consultations for the medical staff (Chen et al. 2020). Some works are devoted to the psychological consequences of quarantine (see the review in Brooks et al. 2020). 

At the same time, in this cluster, there is one publication that thematically belongs to the yellow cluster and was discussed above (Wang et al. 2020). At the border with the brown epidemiological cluster, there is one of the first papers pointing that the virus can be transferred by asymptomatic carriers (Bai et al. 2020). A highly cited paper from the gray cluster supports that finding (Rothe et al. 2020).

Brown cluster: epidemiology and containment policies

The articles in this cluster consider the epidemic containment policies in Singapore (Ng 2020), quarantine policies in China and worldwide (Phelan, Katz, and Gostin 2020) – see the comment on the effectiveness of containment strategies in Anderson et al. (2020). Other studies are devoted to the management of intensive care units (e.g., in Italy: Grasselli, Pesenti, and Cecconi 2020).

Lloyd-Sherlock et al. (2020) argue about the vulnerable position of older adults in low- and middle-income countries. Besides the general considerations about the higher likelihood to get infected and the severity of the disease, the authors mention that older people often raise their grandchildren while the parents work in another country to provide for the family. Therefore little children also become vulnerable during the epidemic. Moreover, in the poorer countries, older adults are often illiterate, which means that during social isolation they are deprived of many communication channels.

Navy cluster: pathology and comorbid diseases

The most cited publications here are the earliest ones, which are devoted to the clinical characteristics of the patients (Yang et al. 2020; Zhang et al. 2020; for a meta-analysis, see Sun et al. 2020), as well as the early publication on the COVID-19 pathology in the USA (Xu et al. 2020). 

Besides the symptoms and the course of the disease, the articles also consider comorbidities that are characteristic of more severe COVID-19 cases and death cases. The most frequent comorbid diseases are hypertension, diabetes, cardiovascular diseases, and respiratory diseases (Zhou et al. 2020; for a systematic review, see Yang et al. 2020). 

The papers also report some specific reactions on the infection, such as cytokine storm (Mehta et al. 2020) in the more severe patients (Zhang et al. 2020), chronic damage to the cardiovascular system (Zheng et al. 2020), liver injuries (Zhang, Shi, and Wang 2020).

Green cluster: drug repurposing

Currently, in the publications here two drugs are discussed that are supposed to effectively inhibit COVID-19. It was found that the antimalarial drug chloroquine and antiviral drug remdesivir successfully inhibit the new coronavirus in vitro (Wang et al. 2020), as well as the less toxic derivative of chloroquine, hydroxychloroquine (Liu et al. 2020). Nowadays all the drugs are tested clinically on COVID-19 patients, and there already is evidence about the effectiveness of chloroquine (Gao, Tian, and Yang 2020).

Purple cluster: radiology; obstetrics

This cluster comprises sever narrower topics. In the upper-right part of the cluster, several papers are located on computer tomography as a means of diagnosing COVID-19 (e.g., Chung et al. 2020; Kanne 2020). 

The articles in the lower part of the cluster investigate if COVID-19 in pregnant women transmits to the newborns. In March, the evidence was published that it can (Dong et al. 2020; Zeng et al. 2020). Chinese experts have published the guidelines for obstetricians working with COVID-19 patients (Chen et al. 2020).

This cluster also contains the paper that makes assumptions about the transmission routes of SARS-CoV-2 based on the biomaterials from COVID-19 patients (Wang et al. 2020). One more highly cited February publication is located here that reports all the then known information about the new coronavirus, reviewing the data on 72,314 cases of infection in China (Wu and McGoogan 2020).

On page 2, we provide links to some general reviews on the novel coronavirus and report our data.