The incidence of the novel coronavirus SARS-CoV-2 among asymptomatic patients: A systematic review

BACKGROUND: The recent outbreak of the coronavirus disease 2019 (COVID-19) has quickly spread globally since its discovery in Wuhan, China, in December 2019. A comprehensive strategy – including surveillance, diagnostics, research, and clinical treatment – is urgently needed to win the battle against COVID-19. Recently, numerous studies have reported the incidence of SARS-CoV-2 in asymptomatic patients. Yet, the incidence and viral transmission from the asymptomatic cases are not yet apparent. AIM: To estimate the incidence of COVID-19 among asymptomatic cases and describe its epidemiological and clinical significance this review systematically examined the published literature on SARS-CoV-2 in asymptomatic patients. METHODS: The literature was searched through four scientific databases: PubMed, Web of Science, Scopus, and Science Direct. RESULTS: Sixty-three studies satisfied the inclusion criteria. The majority of the reported studies were from China. However, there was a lack of SARS-CoV-2 epidemiological studies, from several countries worldwide, tracing the actual incidence of COVID-19, especially in asymptomatic patients. Studies with a large sample size (>1000) estimated that the percentage of people contracting SARS-CoV-2 and likely to be asymptomatic ranged from 1.2–12.9%. However, other studies with a smaller sample size reported a much higher incidence and indicated that up to 87.9% of COVID-19 infected individuals could be asymptomatic. Most of these studies indicated that asymptopatics are a potential source of infection to the community. CONCLUSION: This review highlighted the need for more robust and well-designed studies to better estimate COVID-19 incidence among asymptomatic patients worldwide. Early identification of asymptomatic cases, as well as monitoring and tracing close contacts, could help in mitigating the spread of COVID-19.