Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infectivity by Viral Load, S Gene Variants and Demographic Factors, and the Utility of Lateral Flow Devices to Prevent Transmission.
B.1.1.7 variant
SARS-CoV-2
contact tracing
infectivity
lateral flow device
Journal
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America
ISSN: 1537-6591
Titre abrégé: Clin Infect Dis
Pays: United States
ID NLM: 9203213
Informations de publication
Date de publication:
11 02 2022
11 02 2022
Historique:
received:
30
03
2021
pubmed:
12
5
2021
medline:
17
2
2022
entrez:
11
5
2021
Statut:
ppublish
Résumé
How severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectivity varies with viral load is incompletely understood. Whether rapid point-of-care antigen lateral flow devices (LFDs) detect most potential transmission sources despite imperfect clinical sensitivity is unknown. We combined SARS-CoV-2 testing and contact tracing data from England between 1 September 2020 and 28 February 2021. We used multivariable logistic regression to investigate relationships between polymerase chain reaction (PCR)-confirmed infection in contacts of community-diagnosed cases and index case viral load, S gene target failure (proxy for B.1.1.7 infection), demographics, SARS-CoV-2 incidence, social deprivation, and contact event type. We used LFD performance to simulate the proportion of cases with a PCR-positive contact expected to be detected using 1 of 4 LFDs. In total, 231 498/2 474 066 (9%) contacts of 1 064 004 index cases tested PCR-positive. PCR-positive results in contacts independently increased with higher case viral loads (lower cycle threshold [Ct] values), for example, 11.7% (95% confidence interval [CI] 11.5-12.0%) at Ct = 15 and 4.5% (95% CI 4.4-4.6%) at Ct = 30. B.1.1.7 infection increased PCR-positive results by ~50%, (eg, 1.55-fold, 95% CI 1.49-1.61, at Ct = 20). PCR-positive results were most common in household contacts (at Ct = 20.1, 8.7% [95% CI 8.6-8.9%]), followed by household visitors (7.1% [95% CI 6.8-7.3%]), contacts at events/activities (5.2% [95% CI 4.9-5.4%]), work/education (4.6% [95% CI 4.4-4.8%]), and least common after outdoor contact (2.9% [95% CI 2.3-3.8%]). Contacts of children were the least likely to test positive, particularly following contact outdoors or at work/education. The most and least sensitive LFDs would detect 89.5% (95% CI 89.4-89.6%) and 83.0% (95% CI 82.8-83.1%) of cases with PCR-positive contacts, respectively. SARS-CoV-2 infectivity varies by case viral load, contact event type, and age. Those with high viral loads are the most infectious. B.1.1.7 increased transmission by ~50%. The best performing LFDs detect most infectious cases.
Sections du résumé
BACKGROUND
How severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectivity varies with viral load is incompletely understood. Whether rapid point-of-care antigen lateral flow devices (LFDs) detect most potential transmission sources despite imperfect clinical sensitivity is unknown.
METHODS
We combined SARS-CoV-2 testing and contact tracing data from England between 1 September 2020 and 28 February 2021. We used multivariable logistic regression to investigate relationships between polymerase chain reaction (PCR)-confirmed infection in contacts of community-diagnosed cases and index case viral load, S gene target failure (proxy for B.1.1.7 infection), demographics, SARS-CoV-2 incidence, social deprivation, and contact event type. We used LFD performance to simulate the proportion of cases with a PCR-positive contact expected to be detected using 1 of 4 LFDs.
RESULTS
In total, 231 498/2 474 066 (9%) contacts of 1 064 004 index cases tested PCR-positive. PCR-positive results in contacts independently increased with higher case viral loads (lower cycle threshold [Ct] values), for example, 11.7% (95% confidence interval [CI] 11.5-12.0%) at Ct = 15 and 4.5% (95% CI 4.4-4.6%) at Ct = 30. B.1.1.7 infection increased PCR-positive results by ~50%, (eg, 1.55-fold, 95% CI 1.49-1.61, at Ct = 20). PCR-positive results were most common in household contacts (at Ct = 20.1, 8.7% [95% CI 8.6-8.9%]), followed by household visitors (7.1% [95% CI 6.8-7.3%]), contacts at events/activities (5.2% [95% CI 4.9-5.4%]), work/education (4.6% [95% CI 4.4-4.8%]), and least common after outdoor contact (2.9% [95% CI 2.3-3.8%]). Contacts of children were the least likely to test positive, particularly following contact outdoors or at work/education. The most and least sensitive LFDs would detect 89.5% (95% CI 89.4-89.6%) and 83.0% (95% CI 82.8-83.1%) of cases with PCR-positive contacts, respectively.
CONCLUSIONS
SARS-CoV-2 infectivity varies by case viral load, contact event type, and age. Those with high viral loads are the most infectious. B.1.1.7 increased transmission by ~50%. The best performing LFDs detect most infectious cases.
Identifiants
pubmed: 33972994
pii: 6273394
doi: 10.1093/cid/ciab421
pmc: PMC8136027
doi:
Types de publication
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Langues
eng
Sous-ensembles de citation
IM
Pagination
407-415Subventions
Organisme : Medical Research Council
ID : MR/W02067X/1
Pays : United Kingdom
Informations de copyright
© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.
Références
JAMA. 2020 Aug 4;324(5):510-513
pubmed: 32609307
Lancet Public Health. 2021 Jan;6(1):e30-e38
pubmed: 33308423
Lancet Infect Dis. 2021 May;21(5):629-636
pubmed: 33545090
Nature. 2020 May;581(7809):465-469
pubmed: 32235945
Science. 2021 Apr 9;372(6538):
pubmed: 33658326
Lancet. 2020 May 2;395(10234):e81
pubmed: 32333839
Nature. 2020 Aug;584(7821):430-436
pubmed: 32640463
Ann Intern Med. 2020 Dec 1;173(11):879-887
pubmed: 32790510
JAMA Netw Open. 2020 Dec 1;3(12):e2031756
pubmed: 33315116
JAMA. 2020 Apr 28;323(16):1545-1546
pubmed: 32167538
Lancet. 2020 Mar 14;395(10227):912-920
pubmed: 32112714
EClinicalMedicine. 2021 Jun;36:100924
pubmed: 34101770
PLoS Med. 2020 Sep 22;17(9):e1003346
pubmed: 32960881
Cochrane Database Syst Rev. 2020 Sep 15;9:CD013574
pubmed: 33959956
Lancet Infect Dis. 2020 Aug;20(8):911-919
pubmed: 32353347
N Engl J Med. 2021 Apr 15;384(15):1412-1423
pubmed: 33626250
Science. 2021 Jan 15;371(6526):
pubmed: 33234698