High Asymptomatic Carriage With the Omicron Variant in South Africa

Garrett, Nigel; Tapley, Asa; Andriesen, Jessica; Seocharan, Ishen; Fisher, Leigh; Bunts, Lisa; Espy, Nicole; Wallis, Carole L; Randhawa, April; Miner, Maurine D.; Ketter, Nzeera; Yacovone, Margaret; Goga, Ameena; Huang, Yunda; Hural, John; Kotze, Philip; Bekker, Linda‐Gail; Gray, Glenda; Corey, Lawrence

doi:10.1093/cid/ciac237

Cited by 79 publications

(54 citation statements)

References 14 publications

(12 reference statements)

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“…Current results vary considerably due to different study designs, populations, and regions. Cross-sectional studies have shown that the percentage of asymptomatic Omicron-infected individuals ranged from 7.9% to 61.0% [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ] during the epidemic period of the Omicron variant, while this percentage in cohort studies ranged from 1.23% to 43.7% [ 31 , 32 , 33 , 34 ]. Thus, we conducted a meta-analysis to better understand the percentage of asymptomatic infections among SARS-CoV-2 Omicron variant-positive individuals detected by gene sequencing or specific polymerase chain reaction (PCR).…”

Section: Introductionmentioning

confidence: 99%

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

et al. 2022

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Background: Asymptomatic infections are potential sources of transmission for coronavirus disease 2019, especially during the epidemic of the SARS-CoV-2 Omicron variant. We aimed to assess the percentage of asymptomatic infections among SARS-CoV-2 Omicron variant-positive individuals detected by gene sequencing or specific polymerase chain reaction (PCR). Methods: We searched PubMed, EMBASE, and Web of Science from 26 November 2021 to 13 April 2022. This meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and was registered with PROSPERO (CRD42022327894). Three researchers independently extracted data and two researchers assessed quality using pre-specified criteria. The pooled percentage with 95% confidence interval (CI) of asymptomatic infections of SARS-CoV-2 Omicron was estimated using random-effects models. Results: Our meta-analysis included eight eligible studies, covering 7640 Omicron variant-positive individuals with 2190 asymptomatic infections. The pooled percentage of asymptomatic infections was 32.40% (95% CI: 25.30–39.51%) among SARS-CoV-2 Omicron variant-positive individuals, which was higher in the population in developing countries (38.93%; 95% CI: 19.75–58.11%), with vaccine coverage ≥ 80% (35.93%; 95% CI: 25.36–46.51%), with a travel history (40.05%; 95% CI: 7.59–72.51%), community infection (37.97%; 95% CI: 10.07–65.87%), and with a median age < 20 years (43.75%; 95% CI: 38.45–49.05%). Conclusion: In this systematic review and meta-analysis, the pooled percentage of asymptomatic infections was 32.40% among SARS-CoV-2 Omicron variant-positive individuals. The people who were vaccinated, young (median age < 20 years), had a travel history, and were infected outside of a clinical setting (community infection) had higher percentages of asymptomatic infections. Screening is required to prevent clustered epidemics or sustained community transmission caused by asymptomatic infections of Omicron variants, especially for countries and regions that have successfully controlled SARS-CoV-2.

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Section: Introductionmentioning

confidence: 99%

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

et al. 2022

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“…Therefore, contact transmission is not enough to cause too much concern. In contrast, we found that with the increase of pre-/asymptomatic infections in Omicron strain transmission (Garrett et al, 2022) compared with ancestral strain, airborne route should gain more attention in SARS-CoV-2 transmission and prevention. When the infector was symptomatic, airborne route played a negligible role (<10%), but this pathway became important (34%-38%) when the infector was asymptomatic or presymptomatic.…”

Section: Discussionmentioning

confidence: 77%

“…And droplets from coughing had relative larger size, so most exhaled droplets would deposit on environmental surfaces and inhale by susceptible individuals via droplet route. Concerned about the increase in the proportion of pre-/asymptomatic infections in Omicron strain(Garrett et al, 2022), the study of relative importance different routes in pre-/asymptomatic infection is very significant for SARS-CoV-2 prevention. In addition, for both pre-/asymptomatic and symptomatic infections, though SARS-CoV-2 Omicron variant was more stable on various environmental surfaces than ancestral strain, the contribution of contact route in SARS-CoV-2 transmission increased slightly for Omicron variant.Previous studies had explored the relative contributions of different routes in SARS-CoV-2 ancestral variant transmission, via both animal model(Bao et al, 2020) and mathematical models(Jones, 2020; Mizukoshi et al, 2021).…”

mentioning

confidence: 99%

Slight increase in fomite route transmission risk of SARS-CoV-2 Omicron variant compared with the ancestral strain in households

Wang

Lei

2022

Preprint

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The Omicron SARS-CoV-2 variant has become the dominant lineage worldwide, and experimental study had shown that SARS-CoV-2 Omicron variant was more stable on various environmental surfaces than ancestral strain. However, how the changes of stability on surfaces would influence the role of fomite route in SARS-CoV-2 transmission is still unknown. In this study, we modeled the Omicron and ancestral strain SARS-CoV-2 transmission within a household over 1-day period from multiple pathways, i.e., airborne, droplet and contact route. We assumed there were 2 adults and 1 child in the household, and one of the adults was infected with SARS-CoV-2. We assume a scenario of pre-/asymptomatic infection, i.e., SARS-CoV-2 was emitted by breathing and talking, and symptomatic infection, i.e., SARS-CoV-2 was emitted by breathing, talking, and coughing. In pre-/asymptomatic infection, all three routes contributed a role, contact route contribute most (37%-45%), followed by airborne route (34%-38%) and droplet route (21%-28%). In symptomatic infection, droplet route was the dominant pathway (48%-71%), followed by contact route (25%-42%), airborne route played a negligible role (<10%). In the contact route, indirect contact (fomite) route dominated (contributed more than 97%). Compared with ancestral strain, though the contribution of contact route increased in Omicron variant transmission, the increase was slight, from 25%-41% to 30%-45%.

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“…Droplets from coughing had a relatively larger size, so most exhaled droplets were deposited on environmental surfaces and inhaled by susceptible individuals via the droplet route. With the emerging concern about the increase in the proportion of asymptomatic/presymptomatic infections due to the Omicron strain [ 40 ], evaluating the relative importance of different transmission routes in asymptomatic/presymptomatic infection is critical for SARS-CoV-2 prevention. In addition, in both asymptomatic/presymptomatic and symptomatic infections, although the SARS-CoV-2 Omicron variant was more stable on various environmental surfaces than the ancestral strain, the contribution of the contact route to SARS-CoV-2 transmission increased slightly for the Omicron variant.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, contact transmission is should not be the cause of excessive concern. In contrast, we found that, with the increase in asymptomatic/presymptomatic infections in Omicron strain transmission [ 40 ] compared with the ancestral strain, the airborne route should gain more attention in SARS-CoV-2 transmission and prevention. When the infector was symptomatic, the airborne route played a negligible role (<10%), but this pathway becomes important (34%–38%) when the infector is asymptomatic/presymptomatic.…”

Section: Discussionmentioning

confidence: 99%

Increasing contributions of airborne route in SARS-CoV-2 omicron variant transmission compared with the ancestral strain

Wang²,

Lei³

2022

Building and Environment

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High Asymptomatic Carriage With the Omicron Variant in South Africa

Cited by 79 publications

References 14 publications

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

Percentage of Asymptomatic Infections among SARS-CoV-2 Omicron Variant-Positive Individuals: A Systematic Review and Meta-Analysis

Slight increase in fomite route transmission risk of SARS-CoV-2 Omicron variant compared with the ancestral strain in households

Increasing contributions of airborne route in SARS-CoV-2 omicron variant transmission compared with the ancestral strain

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