Epidemiology, genome, and clinical features of the pandemic SARS-CoV-2: a recent view

Abstract

Since the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, the number of globally confirmed cases according to World Health Organization statistics reached 292 124 in 189 countries by 22 March 2020. The number of deaths reached 12 784, with estimated case-fatality rates ranging from 0.5% to 5.7%. Children population seems to be the least affected by the disease, while the highest rate of death is among the elderly and people with comorbidities. Most infected individuals are asymptomatic or only exhibit mild symptoms. After the incubation period, the most common symptoms are fever, cough and fatigue. Asymptomatic carrier state is of paramount importance because of carriers' ability to spread the infection and to shed the virus into the air and surroundings. Although much is still unknown about SARS-CoV-2, the scientific research is moving at an unprecedented pace towards understanding the nature, effective control, prevention and treatment of SARS-CoV-2. Various reports have suggested an in vivo evolution of the virus, which may explain the rapid spread and changing epidemiology of SARS-CoV-2, but further evidence is needed. Unfortunately, no effective treatment or therapeutic drug is available for the disease; only supportive treatment and classical intervention measures are available for confronting the SARS-CoV-2 pandemic.

Keywords: 2109-nCoV; Asymptomatic; COVID-19; Coronavirus; Epidemic; Europe; Pneumonia; Quarantine; Transmission.

Fig. 1

Structure and genome organization of SARS-CoV-2. (A) General structure of SARS-CoV-2 virion. (B) Genome composition of SARS-CoV-2 shows that 14 ORFs exist. First two ORFs at 5ʹ untranslated region are coding for polyprotein (pp1a/ab) required for virus replication, followed by structural proteins for spike (S), membrane (M) and nucleoprotein (N). At 3ʹ terminus, accessory genes (3a, 3b, p6, 7a, 7b, 8b, 9b and orf14) are located with flanking ORFs. Accessory proteins are not required for virus replication or other known functions. Adapted with permission from Wu et al. [3]. ORF, open reading frame; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Fig. 2

Reported cases of SARS-CoV-2 from 1 to 21 March 2020. (A) Total confirmed cases in all regions of the world. (B) Newly reported cases of SARS-CoV-2 in most affected countries (with >8000 cases). Numbers were obtained from World Health Organization situation reports (https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports). SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.