Monday, September 26, 2022

Researchers conduct a survival systematic review and meta-analysis on asymptomatic and pre-symptomatic SARS-CoV-2

Although studies concerning severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been conducted since its emergence, debate continues about the proportion of asymptomatic infections.

Previous studies have found that the proportion of asymptomatic infections is either overdiagnosed or underestimated, even when patients are adequately followed.

Study: Incidence and transmission potential of asymptomatic and pre-symptomatic SARS-CoV-2 infections: a survival systematic review and meta-analysis. Image credit: hananeko_studio/Shutterstock

Accurate estimation of the proportion of asymptomatic and pre-symptomatic infections is essential for determining the balance and extent of control measures. Previous systematic reviews reported high heterogeneity in estimates of the proportion of asymptomatic and pre-symptomatic infections that could be due to either study differences or chance.

A new study published in Pre-Print Servers medrxiv*Aims to understand and improve the evidence changing over time for three critical review questions using a live systematic review.

The three questions were 1) What proportion of people infected with SARS-CoV-2 do not develop symptoms at all during infection? 2) What is the contagiousness of asymptomatic and pre-symptomatic individuals as compared to symptomatic individuals? 3) What proportion of SARS-CoV-2 transmission is caused by asymptomatic or pre-symptomatic individuals?

about study

The study included a live systematic review where the first research began on 25 March 2020 and was updated on 20 April 2020, 10 June 2020 and 2 February 2021. Studies on asymptomatic and pre-symptomatic SARS-CoV-2 infections were identified with the aid of a search string of medical topic titles and free-text keywords from four electronic databases (Medline, PubMed, Ovid Embase, bioRxiv, and medRxiv).

The study can be in any language and includes examination of symptom status for people who were diagnosed with SARS-CoV-2 by RT-PCR as well as by asymptomatic or pre-symptomatic individuals with SARS-CoV-2 contributed to the transmission. It also included cohort studies, contact tracing and outbreak investigations, case-control studies and mathematical modeling studies. Studies that reported only a proportion of those with pre-symptomatic SARS-CoV-2 and that dealt primarily with people with symptoms were excluded.

Subsequently, data were extracted from the critically selected studies. Extracted variables included study setting, study design, population, country and/or region, gender, age, follow-up period, and primary outcome. Finally, a tool was developed to assess the risk of bias across studies.

test result

The results reported that the present study included a total of 107 selected studies, of which 94 estimated the proportion of people with asymptomatic SARS-CoV-2 infection, 5 reported secondary attacks and 11 reported SARS as either asymptomatic or pre-symptomatic. reported the contribution of infection. COV-2 transmission. Furthermore, of all selected studies, 86 follow-up participants for seven days or longer, 27 followed-up until they had at least one negative RT-PCR test, 19 follow-up participants had a for at least 14 days after known exposure, and 29 involved more than one method of follow-up.

The results indicated that most of the studies included adults of different age groups. In addition, two types of study designs were developed, screening studies and contact and outbreak investigations. It was found that the interquartile range (IQR) for contact and outbreak screening was 8-35 percent and the prediction interval from the random effects meta-analysis was 3-64 percent while for the screening study the IQR was 18-59 percent and the prediction interval was 3-64 percent. was 3-95 percent.

Contact and outbreak investigations were found to be associated with a significant risk of bias, whereas screening studies were found to be associated with a reduced risk of bias. Furthermore, the estimated proportion with asymptomatic infection was found to be similar to the overall estimates when restricted studies with more than ten SARS-CoV-2 infected people.

The risk ratio for secondary attack was found to be 0.43 for asymptomatic to symptomatic infection, whereas for pre-symptomatic to symptomatic infection was found to be 0.71. Furthermore, the contribution of asymptomatic infection to SARS-CoV-2 transmission was found to be less than 10 percent, while the contribution of pre-symptomatic infection was found to be 40 percent or more.

Therefore, the present study indicated that the percentage of individuals with asymptomatic SARS-CoV-2 infection was quite low. Also, most transmissions occurred before symptoms developed. However, physical distancing measures and wearing of masks can prevent transmission from asymptomatic and pre-symptomatic persons. The emergence of the Omicron variant, whose clinical features are not yet known along with vaccination, may further complicate the study of asymptomatic infections. Further studies and systematic reviews should be conducted to learn more about the concerns and effects of both vaccines on asymptomatic and pre-symptomatic SARS-CoV-2 infections.


There are some limitations of the study. First, the study only included studies published as of 2 February 2021. Second, the speed of SARS-CoV-2 related publications exceeded the capacity of the reviewers. Third, although the number of studies is high, the yield is low. Fourth, the four databases included in the study were not comprehensive. Fifth, the study did not consider the potential impact of false-negative RT-PCR results. Finally, no published studies on people infected with the SARS-CoV-2 variant of concern or vaccination were found.

*Important Information

medrxiv Publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, should guide clinical practice/health-related behavior, or be regarded as established information.


Nation World News Desk
Nation World News Desk
Nation World News is the fastest emerging news website covering all the latest news, world’s top stories, science news entertainment sports cricket’s latest discoveries, new technology gadgets, politics news, and more.
Latest news
Related news
- Advertisement -