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Summary
Background
Despite circumstantial proof for aerosol and fomite unfold of SARS-CoV-2, empirical information linking both pathway with transmission are scarce. Here we aimed to evaluate whether or not the presence of SARS-CoV-2 on frequently-touched surfaces and residents’ fingers was a predictor of SARS-CoV-2 family transmission.
Methods
In this longitudinal cohort research, in the course of the pre-alpha (September to December, 2020) and alpha (B.1.1.7; December, 2020, to April, 2021) SARS-CoV-2 variant waves, we prospectively recruited contacts from households uncovered to newly identified COVID-19 main circumstances, in London, UK. To maximally seize transmission occasions, contacts had been recruited no matter symptom standing and serially examined for SARS-CoV-2 an infection by RT-PCR on higher respiratory tract (URT) samples and, in a subcohort, by serial serology. Contacts’ fingers, main circumstances’ fingers, and frequently-touched surface-samples from communal areas had been examined for SARS-CoV-2 RNA. SARS-CoV-2 URT isolates from 25 main case-contact pairs underwent whole-genome sequencing (WGS).
Findings
From Aug 1, 2020, till March 31, 2021, 620 contacts of PCR-confirmed SARS-CoV-2-infected main circumstances had been recruited. 414 family contacts (from 279 households) with out there serial URT PCR outcomes had been analysed within the full family contacts’ cohort, and of these, 134 contacts with out there longitudinal serology information and never vaccinated pre-enrolment had been analysed within the serology subcohort. Household an infection price was 28·4% (95% CI 20·8–37·5) for pre-alpha-exposed contacts and 51·8% (42·5–61·0) for alpha-exposed contacts (p=0·0047). Primary circumstances’ URT RNA viral load didn’t correlate with transmission, however was related to detection of SARS-CoV-2 RNA on their fingers (p=0·031). SARS-CoV-2 detected on main circumstances’ fingers, in flip, predicted contacts’ danger of an infection (adjusted relative danger [aRR]=1·70 [95% CI 1·24–2·31]), as did SARS-CoV-2 RNA presence on family surfaces (aRR=1·66 [1·09–2·55]) and contacts’ fingers (aRR=2·06 [1·57–2·69]). In six contacts with an preliminary adverse URT PCR outcome, hand-swab (n=3) and family surface-swab (n=3) PCR positivity preceded URT PCR positivity. WGS corroborated family transmission.
Interpretation
Presence of SARS-CoV-2 RNA on main circumstances’ and contacts’ fingers and on frequently-touched family surfaces associates with transmission, figuring out these as potential vectors for unfold in households.
Funding
National Institute for Health Research Health Protection Research Unit in Respiratory Infections, Medical Research Council.
Introduction
but our understanding of the routes of transmission stays an space of ongoing scientific debate. Despite public steerage on self-isolation, facemask carrying, handwashing, and floor and air decontamination, there may be little or no empirical proof for the pathways via which the virus spreads. Modelling and epidemiological observations implicate viral unfold via massive respiratory droplets that decide on surfaces from the place virus is transferred to contacts’ mucosal membranes, often called fomite unfold, in addition to airborne unfold via smaller, aerosolised droplets instantly inhaled by contacts.
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in addition to in exhaled and ambient air from hospitalised sufferers with COVID-19,
,
its detection on potential vectors has not hitherto been proven to correlate with transmission. This hole in information hampers correct modelling of illness transmission and growth of evidence-based public well being steerage,
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which stay essential given the flexibility of SARS-CoV-2 to unfold via extremely vaccinated populations.
,
As isolation restrictions for family contacts have now been lifted, understanding the danger components and pathways of transmission inside households has develop into more and more essential to forestall the unfold of SARS-CoV-2.
Evidence earlier than this research
Extensive literature on SARS-CoV-2 transmission has been revealed, with several types of research (observational potential cohort research, retrospective cohort research, modelling, case-control, and so on) evaluating transmission in several situations and populations. Although most transmission globally happens in households, the vectors and pathways of family SARS-CoV-2 transmission stay poorly understood and there may be ongoing scientific debate as to the predominant modes of transmission. We looked for the phrases “SARS-CoV-2” AND “household” AND “transmission” with “pathways” OR “surface” OR “hand” OR “fomite” OR “droplet” in PubMed for articles revealed from database inception up till Nov 2, 2022, in English. After omitting research with completely different settings or research populations (hospitalised populations, health-care staff, colleges, care houses, and so on), we recognized few research assessing SARS-CoV-2 in family settings. Several systematic and non-systematic opinions have been revealed on family an infection price, usually denoted as secondary assault price, and a few research have evaluated the contribution of demographic, scientific, and epidemiological components to an infection (intercourse, age, vaccinations standing, co-infection, comorbidities, relation to the first case, family traits, and so on). At the time of writing, solely six research reported the presence of viral RNA on family surfaces, however none have correlated this presence to danger of an infection amongst contacts. Additionally, we discovered no research analysing the presence of viral RNA on main circumstances’ or contacts’ fingers, which could be essential vectors of transmission.
Added worth of this research
We prospectively enrolled symptomatic and asymptomatic family contacts not too long ago uncovered to their main circumstances, and serially carried out higher respiratory tract swabs RT-PCR testing, and when consented, collected blood samples for serial serology. Additionally, we additionally took swabs from regularly touched family surfaces, and first circumstances’ and contacts’ fingers, and examined them for presence of SARS-CoV-2 RNA. Our potential research design and dense longitudinal testing of contacts enabled us to maximally seize secondary COVID-19 circumstances amongst family contacts. Epidemiological linkage and whole-genome sequencing of main and secondary circumstances’ SARS-CoV-2 isolates confirmed family transmission. Presence of SARS-CoV-2 RNA on main circumstances’ fingers, family surfaces, and contacts’ fingers strongly correlated with contacts’ danger of an infection. To our information, this research gives the primary empirical information linking detection of SARS-CoV-2 on candidate vectors of transmission. This research additionally recognized main circumstances’ fingers, family surfaces, and contacts’ fingers as potential vectors of transmission. Aerosol transmission was not investigated on this research and due to this fact can’t be excluded as a possible route of family unfold.
Implications of all of the out there proof
This research, to our information, is the primary to establish a correlation between SARS-CoV-2 RNA on candidate vectors and an infection of contacts. These longitudinal empirical information from a real-world neighborhood setting considerably advance our understanding of SARS-CoV-2 family unfold, which is the setting of most transmission globally. Our findings assist interventions comparable to frequent handwashing, floor cleaning, bodily distancing, lowering direct contact, and use of masks to scale back transmission in households.
Moreover, virtually all contacts’ an infection price estimates use higher respiratory tract (URT) PCR testing at a single timepoint to detect or exclude an infection,
limiting the flexibility to detect new secondary infections.
We due to this fact prospectively recruited inclined family contacts not too long ago uncovered to PCR-positive COVID-19 main circumstances. We serially sampled each symptomatic and asymptomatic contacts’ URT for PCR testing and, when consented, blood for serial serology. We examined for the presence of SARS-CoV-2 RNA on main circumstances’ and contacts’ fingers and frequently-touched surfaces. We aimed to evaluate whether or not the presence of SARS-CoV-2 on a number of of those candidate vectors would prospectively predict SARS-CoV-2 transmission.
Methods
Study design and contributors
Participants had been enrolled in two longitudinal community-based observational research in Greater London, UK: Integrated Network for Surveillance, Trials and Investigations into COVID-19 Transmission (INSTINCT), and Assessment of Transmission And Contagiousness of COVID-19 in Contacts (ATACCC). Ethics approval was obtained from the Health Research Authority (20/NW/0231).
SARS-CoV-2 PCR-positive, symptomatic main circumstances (outlined as the primary detected PCR-positive case within the family) and their contacts had been recognized via the nationwide contact tracing system (National Health Service Test & Trace) and invited to take part by UK Health Security Agency (UKHSA) workers between Aug 1, 2020, and March 31, 2021. The research interval included the pre-alpha (September to December 2020) and alpha (B.1.1.7; December, 2020, to April, 2021) waves of SARS-CoV-2, when vaccination protection was low and social distancing insurance policies had been in place. Contacts had been deemed family contacts if resident on the similar tackle as their main case.
Figure 1INSTINCT and ATACCC research recruitment timelines (A), and inclusion standards, publicity, and SARS-CoV-2 an infection standing of contacts included within the analyses (B)
Participants had been free to depart the research prematurely in the event that they wished or to omit some sociodemographic attribute data. Among the visited contributors, not all agreed to provide all forms of samples (serological, floor swabs, and hand swabs).
Two contacts cohorts had been outlined for evaluation: the total family contacts’ cohort, consisting of all family contacts with longitudinal (≥3) URT samples, and the serology subcohort, consisting of the contacts throughout the full cohort who additionally had longitudinal serology information (ie, serological information out there at day 0 and a minimum of one different timepoint), had been recognized to be unvaccinated earlier than enrolment, and had been seronegative at enrolment. Households with co-primary circumstances (concurrent PCR positivity) had been excluded.
to evaluate family deprivation in accordance with postcodes. Participants gave written knowledgeable consent.
Procedures
and UKHSA Colindale, London, UK (ATACCC) with comparable sensitivity and specificity (appendix pp 2–3). Serology was carried out utilizing a hybrid double antigen binding assay (DABA), as beforehand described (appendix pp 3–4).
A DABA degree of lower than 1 indicated seronegativity and a DABA degree of 1 or extra indicated seropositivity. A DABA degree of lower than 1 at day 0 that elevated by 3 within the binding ratio within the first 28 days after participant enrolment (if PCR optimistic) or within the first 14 days after enrolment (if PCR adverse) indicated seroconversion. Variant standing was assigned via S-gene goal failure standing (ATACCC; appendix p 5) and whole-genome sequencing (WGS; INSTINCT; appendix pp 5–6). Libraries for WGS had been generated with the EasySeq RT-PCR SARS-CoV-2 (novel coronavirus) WGS package v1 or v2 (Nimagen, Nijmegen, Netherlands) and an iSeq 100 gadget was used for sequencing (Illumina, San Diego, CA, USA). Hand swabs and floor swabs had been examined for RNA presence on the Department of Infectious Disease, Imperial College London, London, UK (appendix p 4).
PCR-positive hand and floor swabs with a cycle threshold (Ct) of lower than 33 had been subjected to viral tradition in a mammalian cell line-based in vitro assay (appendix pp 4–5). Swabs had been maintained at 4°C for 36–72 h till tradition was carried out, reflecting the time for transportation from residents’ houses and laboratory storage whereas RT-PCR was carried out. Further assay particulars are discovered within the appendix (pp 2–6).
Statistical evaluation
Household an infection price was calculated because the proportion of contacts who grew to become PCR optimistic or contaminated amongst all these examined.
Binary indicators for an infection or PCR optimistic versus PCR adverse candidate vectors had been used. The mannequin was adjusted for vital demographic covariates and covariates related to family traits recognized with univariable analyses.
Role of the funding supply
The funder of the research had no position in research design, information assortment, information evaluation, information interpretation, or writing of the report.
Results
Table 1Baseline demographic and scientific traits of family contacts uncovered to PCR-confirmed SARS-CoV-2 main circumstances, within the full family contacts’ cohort and within the serial serology subcohort.
Data are n (%) except in any other case indicated. NA=not relevant.
Table 2SARS-CoV-2 family an infection price within the full family contacts’ cohort and within the serial serology subcohort, stratified by kind of publicity to the first case and family traits
Household an infection price is given because the proportion of PCR-positive contacts within the full family contact cohort (n=414), and because the proportion of contaminated (PCR-positive or seroconverted) contacts within the serial serology subcohort (n=134). Primary case maximum-measured URT RNA viral load classes had been divided to provide comparable variety of contacts. URT=higher respiratory tract.
All PCR-positive floor swabs and first circumstances’ hand swabs, and a lot of the PCR-positive hand swabs from the contacts (16 [72%] of twenty-two), had been optimistic on the day of enrolment. This RNA detection on floor and hand swabs was simultaneous in time with the primary detection of SARS-CoV-2 in prevalent PCR-positive contacts’ respective URT swabs, at day 0. Of the 31 PCR-positive contacts with incident an infection (ie, with initially PCR-negative URT swabs), 14 had family floor samples collected, of which three had been optimistic—all had been optimistic at day 0, earlier than the respective contacts’ URT swabs changing into PCR optimistic. 19 of 31 contacts with incident an infection had hand swabs collected, of which seven had been optimistic. In three contacts, hand swabs had been already PCR optimistic earlier than their respective URT swabs changing into optimistic. In the remaining 4 contacts, hand swabs had been optimistic on the second time-point (day 7); therefore, it’s not potential to temporally resolve whether or not these contacts’ fingers grew to become PCR optimistic earlier than or after their URT swabs grew to become PCR optimistic.
Table 3Detection of SARS-CoV-2 on environmental surfaces, and on the fingers of the contact and first case, by PCR-status within the full family contacts’ cohort, and by an infection standing within the serology evaluation contacts’ subcohort
Data are n (%) except in any other case indicated. Relative danger estimates from the multivariable analyses had been calculated with a modified Poisson regression utilizing strong normal errors, accounting for family clustering, and adjusting for contact’s intercourse assigned at delivery, comorbidity standing, vaccination pre-enrolment standing, relationship standing to the first case, and ratio variety of residents within the family to variety of bedrooms.
Figure 2Measured SARS-CoV-2 RNA viral load in PCR-positive environmental samples, stratified by contacts’ URT PCR standing and baseline serological standing
Only contacts linked to a number of PCR-positive environmental samples are depicted. (A) Primary circumstances’ hand-swab RNA viral load (median 82·09 copies per mL, IQR 46·09–1082·29). (B) Household surface-swab RNA viral load (226·58, 101·38–602·51). (C) Contacts’ hand-swab RNA viral load (117·66, 21·75–244·39). The measured environmental viral hundreds don’t differ by contacts’ URT PCR standing, as proven by the p values in every panel (Mann-Whitney U take a look at). All optimistic main case hand swabs and floor swabs had been collected on day 0, whereas contacts’ hand swabs had been optimistic on day 0 (n=16) and day 7 (n=6). Environmental samples with greater than 5 RNA copies per mL had been thought of PCR optimistic. URT=higher respiratory tract.
strongly supporting family transmission because the supply of an infection in all contaminated contacts sequenced.
Figure 3Genomic proof of SARS-CoV-2 transmission amongst households
Genomic evaluation of 25 households (comprising 35 contacts and 25 of their respective epidemiologically linked main circumstances) of non-synonymous mutations throughout the SARS-CoV-2 genome, to evaluate whether or not the identical or completely different strains are current throughout the family. Genomic analyses had been carried out the place higher respiratory tract swabs with viral a great deal of greater than 200 copies per mL had been out there for each main circumstances and speak to(s).
Discussion
,
,
this research is, to our information, the primary to establish correlations between SARS-CoV-2 RNA on candidate vectors with contacts’ an infection danger. These longitudinal empirical information from a real-world neighborhood setting with rigorously outlined an infection outcomes considerably advance our understanding of SARS-CoV-2 family unfold, the setting of most transmission globally.
This discovering most likely displays our rigorous, intensive sampling strategy, which captured the next proportion of transmission to inclined contacts than earlier research.
,
,
,
however in keeping with others,
main case SARS-CoV-2 RNA viral load in URT samples didn’t correlate with contacts’ danger of an infection in our cohort. Interestingly, nevertheless, main circumstances’ RNA viral load in URT samples did predict their danger of getting a SARS-CoV-2 PCR-positive hand swab, which in flip was related to transmission to their respective contacts. Presence of viral RNA on regularly touched family surfaces strongly related to contacts’ danger of getting a PCR-positive hand swab and predicted contacts’ danger of an infection. Moreover, presence of SARS-CoV-2 RNA on contacts’ fingers correlated with presence of viral RNA on their respective main circumstances’ fingers and with contacts’ personal danger of SARS-CoV-2 an infection.
SARS-CoV-2 was cultured from one in every of these contacts’ hand swabs, displaying the presence of stay, infectious virus on the fingers of this particular person. WGS confirmed that the viral isolates from the contact’s hand and URT had been indistinguishable. Conversely, in non-incident contacts who already had PCR-positive URT samples at enrolment, the corresponding PCR-positive hand and family floor swabs had been additionally constantly optimistic at enrolment.
Among all contacts with a number of optimistic candidate vector samples, no variations had been noticed within the RNA viral load quantified on these vectors between contacts with PCR-positive and PCR-negative URT samples, suggesting that the supply of the SARS-CoV-2 RNA on these vectors was unlikely to be retrograde contamination from the contacts’ URT. Notably, contacts with PCR-negative URT samples and with viral RNA detected on their fingers, their main circumstances’ fingers, or family surfaces, predominantly had pre-existing immunity, as evidenced by being seropositive at enrolment. By distinction, only a few contacts with PCR-positive URT samples linked to optimistic hand swabs or floor swabs of their households had been seropositive at enrolment. This discovering means that the presence of SARS-CoV-2 RNA on candidate vectors linked to uninfected contacts with PCR-negative URT samples may not have resulted in an infection due to their pre-existing immunity.
,
To our information, our information are the primary empirical proof to correlate presence of SARS-CoV-2 RNA on candidate vectors with contacts’ danger of an infection. However, our findings don’t show causality. SARS-CoV-2 unfold is believed to be predominantly via airborne transmission,
,
,
which should be the only route in a number of settings, together with these involving long-range transmission.
The transmission we noticed might due to this fact have been completely airborne and the presence of SARS-CoV-2 RNA on residents’ fingers and family surfaces would possibly mirror bystander contamination by massive respiratory droplets that could be generated alongside infectious aerosols that mediate transmission. We didn’t systematically pattern air within the households so we can’t exclude this chance.
To show causality of both fomite or airborne transmission, a extremely managed synthetic experiment could be required, during which SARS-CoV-2-naive, wholesome, sentinel contributors could be confined in an atmosphere beforehand contaminated by an infectious-case. Experimental interventions testing the results of full air trade or decontamination versus floor decontamination earlier than the contributors’ confinement would then be correlated with their subsequent an infection standing. Although such an experimental design would possibly affirm the route of transmission, it will not mirror the real-world setting of neighborhood transmission with its pure spectrum of environmental circumstances and host components.
Our research has a number of limitations. We can’t exclude that in a proportion of main case–contact pairs the place the prevalent contaminated contact may need been asymptomatic or pre-symptomatic, the contact may need been the preliminary supply of transmission, or that the contact may need been contaminated from exterior of the family. These situations are unlikely for a lot of the households, as a result of our task of case–contact pairs is underpinned by epidemiological linkage between every main case and their respective contact(s), and additional corroborated by WGS of SARS-CoV-2 isolates from main circumstances and their contacts in all 25 households the place this was potential. Similarly, though among the contacts’ infections might probably have been tertiary somewhat than secondary to the first case, we think about this unlikely as a result of contacts had been enrolled on common 3 days after symptom onset of the first case. The likelihood of an infection arising from exterior the family was low as a result of London was in a state of lockdown throughout our research, leading to very restricted social or occupational contact exterior of households. A corollary of this level, nevertheless, is that our family an infection price estimate may not be generalisable to households in settings the place societal non-pharmaceutical interventions aren’t in power with correspondingly much less contact time between cohabitants.
We didn’t systematically accumulate behavioural data on hygiene practices and bodily distancing, as preventative measures sometimes passed off after main case symptom onset, when publicity had already occurred, limiting the impact of such practices on lowering contacts’ danger of an infection. Additionally, the gathering of such behavioural information would have been biased by the contributors’ conditioning of the underlying circumstances (eg, lockdown and participation in an observational research) and wouldn’t symbolize their typical practices.
The households that consented to take part may not be consultant of the overall inhabitants as a result of non-White ethnicities and older age teams had been under-represented. In some households, solely a proportion of cohabitants had been recruited; nevertheless, an infection price in households the place all contacts had been recruited approximated the an infection price within the full family contact cohort. Although the research may very well be biased by the distinction between household-visited contacts and remotely recruited contacts, these teams had been comparable.
,
whereas different proof suggests elevated probability for aerosol transmission relative to earlier variants.
,
various interventions to impede transmission are urgently wanted. The simple public well being interventions and messaging underpinned by our proof present a well timed, pragmatic element of the longer term toolkit for residing safely with COVID-19.
The INSTINCT and ATACCC research group investigators
Jessica Cutajar, Valerie Quinn, Sarah Hammett, Eimèar McDermott, Constanta Luca, Kristel Timcang, Jada Samuel, Samuel Bremang, Samuel Evetts, Lulu Wang, Sean Nevin, Megan Davies, Chitra Tejpal, Mohammed Essoussi, Anjeli V Ketkar, Giulia Miserocchi, Harriet Catchpole, Michael G Whitfield, Alexandra Kondratiuk (NIHR Health Protection Research Unit in Respiratory Infections, National Heart and Lung Institute, Imperial College London, London, UK). Anjna Badhan, Simon Dustan, Isaac J Day Weber, Federica Marchesin (Section of Virology, Department of Infectious Disease, Imperial College London, London, UK). John Poh (UK Health Security Agency, London, UK).
Contributors
RK, RV, JF, TDP, SHak, and AL designed the research and information assortment methodology. RV, JD, JLB, JF, RK, SHak, EC, JSN, MRT-W, ND, AKoy, JC, VQ, SHam, EMcD, CL, KT, JS, SB, SE, LW, SN, MD, CT, GM, HC, AKon, RT, WSB, GPT, and MZ did administrative and technical research logistics. ND, AKoy, CT, ME, GM, AVK, HC, MGW, KJM, and JLB acquired information. LM, CR, PW, AB, SD, PSF, JP, GPT, and MZ analysed the RT-PCR information. EP, IJDW, FM, MOM, and RT analysed the serology information. JZ and WSB analysed the environmental (floor swabs and hand swabs) information. CA, MAC, LM, GPT, and PSF analysed the sequencing information and S-gene goal failure information. ND, NMF, and AL conceived the work and design of analyses. ND and AKoy analysed the information. ND, AKoy, TDP, SHak, AS, and AL interpreted the information. ND, AKoy, SHak, and AL drafted the manuscript. SHak, JF, TDP, HH, AS, EC, and AL reviewed the manuscript. AL is the principal investigator for INSTINCT. AL and JD are the principal investigators for ATACCC. ND and AKoy instantly accessed and verified the underlying information of the research. All authors contributed essential mental content material throughout manuscript drafting or revision and settle for accountability for the general work by making certain that questions pertaining to the accuracy or integrity of any portion of the work are appropriately investigated and resolved. All authors had full entry to all the information within the research and had remaining accountability for the choice to submit for publication.
Data sharing
An anonymised, deidentified model of the dataset might be made out there upon request to the corresponding creator to permit all outcomes to be reproduced.
Declaration of pursuits
NMF studies grants from the UK Medical Research Council, UK National Institute of Health and Care Research, UK Research and Innovation, Community Jameel, Janssen Pharmaceuticals, Bill & Melinda Gates Foundation, and Gavi, the Vaccine Alliance; consulting charges from the World Bank; fee or honoraria from the Wellcome Trust; journey bills from WHO; advisory board participation for Takeda; and is a senior editor of the eLife journal. All different authors declare no competing pursuits.
Acknowledgments
This work is supported by the NIHR Health Protection Research Units (HPRU) in Respiratory Infections (NIHR200927), in partnership with the UK Health Security Agency. JZ and WSB are supported by funding supplied via PROTECT COVID-19 National Core Study and Genotype-to-Phenotype UK National Virology Consortium (G2P-UK), funded by the Medical Research Council (MRC; MR/W005611/1), which additionally partially funded this work. AS is supported by an NIHR educational scientific lectureship. PSF and MAC are supported by the UK Dementia Research Institute. JD is supported by the NIHR HPRU in Emerging and Zoonotic Infections. GPT is supported by the Imperial NIHR Biomedical Research Centre. NMF is supported by UK Research and Innovation (UKRI) MRC (Centre for Global Infectious Disease Analysis [MR/R015600/1] and MRC UKRI/DHSC NIHR COVID-19 speedy response name [MR/V038109/1]), NIHR HPRU in Modelling and Health Economics [NIHR200908], and philanthropic funding from Community Jameel. We thank all of the contributors who had been concerned within the research, UK Health Security Agency workers for facilitating recruitment into the research, and the workers of the Virus Reference Department for performing PCR and sequencing assays. We additionally thank Tamara Hopewell, Holly Grey, Jessica Grey, and Niamh Nichols for offering additional logistical assist. Finally, we thank the Molecular Diagnostics Unit at Imperial College London.
Supplementary Material
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Published: April 06, 2023
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Linked Articles
- Assessing the potential for fomite transmission of SARS-CoV-2
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Over the course of the COVID-19 pandemic the routes of SARS-CoV-2 transmission have remained highly contentious.1 Respiratory viruses such as SARS-CoV-2 are thought to spread directly from one person to another through the air, typically during prolonged close contact, but there is a possibility that fomites might also play a role.2 Fomites are objects in the environment on which infectious virions can survive, acting as a vector for person-to-person transmission. For fomite transmission to occur there must be sufficient infectious virus shed into the environment and it must persist ex vivo at sufficiently high titres such that it is able to establish an infection upon exposure to the mucosal surfaces of a susceptible individual.
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