Semra Tibebu

Bio: Semra Tibebu is an academic researcher. The author has contributed to research in topics: Retrospective cohort study & Population. The author has an hindex of 3, co-authored 4 publications receiving 14 citations.

Increased household secondary attacks rates with Variant of Concern SARS-CoV-2 index cases.

Abstract: We compared secondary attack rates in households with B.1.1.7 variant of concern (VOC) versus non-VOC index cases in a matched cohort in Ontario, Canada. The secondary attack rate for VOC index cases was 1.31 times higher than non-VOC index cases. This increase was particularly accentuated for asymptomatic or presymptomatic index cases.

Household secondary attack rate of COVID-19 by household size and index case characteristics

Abstract: In this population-wide study in Ontario, Canada, we investigated the household secondary attack rate (SAR) to understand its relationship to household size and index case characteristics. We identified all patients with confirmed COVID-19 between July 1 and November 30, 2020. Cases within households were matched based on reported residential address; households were grouped based on the number of household contacts. The majority of households (68.2%) had a SAR of 0%, while 3,442 (11.7%) households had a SAR [≥]75%. Overall household SAR was 19.5% and was similar across household sizes, but varied across index case characteristics. Households where index cases had longer delays between symptom onset and test seeking, households with older index cases, households with symptomatic index cases, and larger households located in diverse neighborhoods, were associated with greater household SAR. Our findings present characteristics associated with greater household SARs and proposes immediate testing as a method to reduce household transmission and incidence of COVID-19.

Comparative Household Secondary Attack Rates associated with B.1.1.7, B.1.351, and P.1 SARS-CoV-2 Variants

Abstract: BackgroundThe emergence of SARS-CoV-2 variants associated with increased transmissibility are driving a 3rd global surge in COVID-19 incidence. There are currently few reliable estimates for the P.1 and B.1.351 lineages. We sought to compare the secondary attack rates of SARS-COV-2 mutations and variants in Canadas largest province of Ontario, using a previously validated household-based approach. MethodsWe identified individuals with confirmed SARS-CoV-2 infection in Ontarios provincial reportable disease surveillance system. Cases were grouped into households based on reported residential address. Index cases had the earliest of symptom onset in the household. Household secondary attack rate was defined as the percentage of household contacts identified as secondary cases within 1-14 days after the index case. ResultsWe identified 26,888 index household cases during the study period. Among these, 7,555 (28%) were wild-type, 17,058 (63%) were B.1.1.7, 1674 (6%) were B.1.351 or P.1, and 601 (2%) were non-VOC mutants (Table 1). The secondary attack rates, according to index case variant were as follows: 20.2% (wild-type), 25.1% (B.1.1.7), 27.2% (B.1.351 or P.1), and 23.3% (non-VOC mutants). In adjusted analyses, we found that B.1.1.7, B.1.351, and P.1 index cases had the highest transmissibility (presumptive B.1.1.7 ORadjusted=1.49, 95%CI 1.36, 1.64; presumptive B.1.351 or P.1 ORadjusted=1.60, 95%CI 1.37, 1.87). O_TBL View this table: org.highwire.dtl.DTLVardef@1f1a4e9org.highwire.dtl.DTLVardef@181f042org.highwire.dtl.DTLVardef@1c483fborg.highwire.dtl.DTLVardef@b4fba0org.highwire.dtl.DTLVardef@1f3d626_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable 1.C_FLOATNO O_TABLECAPTIONSecondary attack rates of persons infected with SARS-CoV-2, March 1 to April 17. C_TABLECAPTION C_TBL DiscussionSubstantially higher transmissibility associated with variants will make control of SARS-CoV-2 more difficult, reinforcing the urgent need to increase vaccination rates globally.

Increased household secondary attacks rates with Variant of Concern SARS-CoV-2 index cases

Abstract: IMPORTANCEHigher secondary attack rates related to variant of concern (VOC) index cases have been reported, but have not been explored within households, which continue to be an important source of coronavirus disease 2019 (COVID-19) transmission OBJECTIVETo compare secondary attack rates in households with VOC versus non-VOC index cases DESIGNA retrospective cohort study of household index cases reported from February 7 - 27, 2021 A propensity-score matched cohort was derived to calculate adjusted estimates SETTINGOntario, Canada PARTICIPANTSA population-based cohort of all private households with index cases We excluded cases in congregate settings, as well as households with one individual or with >1 case with the same earliest symptom onset date EXPOSUREVOC status, defined as either individuals confirmed as B117 using whole genome sequencing or those that screened positive for the N501Y mutation using real-time PCR MAIN OUTCOME AND MEASUREHousehold secondary attack rate, defined as the number of household secondary cases that occurred 1-14 days after the index case divided by the total number of household secondary contacts RESULTSWe included 1,259 index VOC and non-VOC cases in the propensity score-matched analysis The secondary attack rate for VOC index cases in this matched cohort was 131 times higher than non-VOC index cases (RR=131, 95%CI 114-149), similar to the unadjusted estimate In stratified analyses, the higher secondary attack rate for VOC compared to non-VOC index cases was accentuated for asymptomatic index cases (RR=191, 95% CI 096-380) and presymptomatic cases (RR=341, 95%CI 113-1026) CONCLUSIONS AND RELEVANCEThis study provides strong evidence of increased transmissibility in households due to VOCs and suggests that asymptomatic and pre-symptomatic transmission may be of particular importance for VOCs Our study suggests that more aggressive public health measures will be needed to control VOCs and that ongoing research is needed to understand mechanisms of VOC transmissibility to curb their associated morbidity and mortality

The Disease Severity and Clinical Outcomes of the SARS-CoV-2 Variants of Concern

Abstract: With the continuation of the pandemic, many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have appeared around the world. Owing to a possible risk of increasing the transmissibility of the virus, severity of the infected individuals, and the ability to escape the antibody produced by the vaccines, the four SARS-CoV-2 variants of Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2) have attracted the most widespread attention. At present, there is a unified conclusion that these four variants have increased the transmissibility of SARS-CoV-2, but the severity of the disease caused by them has not yet been determined. Studies from June 1, 2020 to October 15, 2021 were considered, and a meta-analysis was carried out to process the data. Alpha, Beta, Gamma, and Delta variants are all more serious than the wild-type virus in terms of hospitalization, ICU admission, and mortality, and the Beta and Delta variants have a higher risk than the Alpha and Gamma variants. Notably, the random effects of Beta variant to the wild-type virus with respect to hospitalization rate, severe illness rate, and mortality rate are 2.16 (95%CI: 1.19–3.14), 2.23 (95%CI: 1.31–3.15), and 1.50 (95%CI: 1.26–1.74), respectively, and the random effects of Delta variant to the wild-type virus are 2.08 (95%CI: 1.77–2.39), 3.35 (95%CI: 2.5–4.2), and 2.33 (95%CI: 1.45–3.21), respectively. Although the emergence of vaccines may reduce the threat posed by SARS-CoV-2 variants, these are still very important, especially the Beta and Delta variants.

Household Secondary Attack Rates of SARS-CoV-2 by Variant and Vaccination Status

Abstract: This systematic reviewe and meta-analysis evaluates household secondary attack rates of SARS-CoV-2 by variant and vaccination status.

Factors Associated With Household Transmission of SARS-CoV-2: An Updated Systematic Review and Meta-analysis.

Abstract: Importance A previous systematic review and meta-analysis of household transmission of SARS-CoV-2 that summarized 54 published studies through October 19, 2020, found an overall secondary attack rate (SAR) of 16.6% (95% CI, 14.0%-19.3%). However, the understanding of household secondary attack rates for SARS-CoV-2 is still evolving, and updated analysis is needed. Objective To use newly published data to further the understanding of SARS-CoV-2 transmission in the household. Data sources PubMed and reference lists of eligible articles were used to search for records published between October 20, 2020, and June 17, 2021. No restrictions on language, study design, time, or place of publication were applied. Studies published as preprints were included. Study selection Articles with original data that reported at least 2 of the following factors were included: number of household contacts with infection, total number of household contacts, and secondary attack rates among household contacts. Studies that reported household infection prevalence (which includes index cases), that tested contacts using antibody tests only, and that included populations overlapping with another included study were excluded. Search terms were SARS-CoV-2 or COVID-19 with secondary attack rate, household, close contacts, contact transmission, contact attack rate, or family transmission. Data extraction and synthesis Meta-analyses were performed using generalized linear mixed models to obtain SAR estimates and 95% CIs. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Main outcomes and measures Overall household SAR for SARS-CoV-2, SAR by covariates (contact age, sex, ethnicity, comorbidities, and relationship; index case age, sex, symptom status, presence of fever, and presence of cough; number of contacts; study location; and variant), and SAR by index case identification period. Results A total of 2722 records (2710 records from database searches and 12 records from the reference lists of eligible articles) published between October 20, 2020, and June 17, 2021, were identified. Of those, 93 full-text articles reporting household transmission of SARS-CoV-2 were assessed for eligibility, and 37 studies were included. These 37 new studies were combined with 50 of the 54 studies (published through October 19, 2020) from our previous review (4 studies from Wuhan, China, were excluded because their study populations overlapped with another recent study), resulting in a total of 87 studies representing 1 249 163 household contacts from 30 countries. The estimated household SAR for all 87 studies was 18.9% (95% CI, 16.2%-22.0%). Compared with studies from January to February 2020, the SAR for studies from July 2020 to March 2021 was higher (13.4% [95% CI, 10.7%-16.7%] vs 31.1% [95% CI, 22.6%-41.1%], respectively). Results from subgroup analyses were similar to those reported in a previous systematic review and meta-analysis; however, the SAR was higher to contacts with comorbidities (3 studies; 50.0% [95% CI, 41.4%-58.6%]) compared with previous findings, and the estimated household SAR for the B.1.1.7 (α) variant was 24.5% (3 studies; 95% CI, 10.9%-46.2%). Conclusions and relevance The findings of this study suggest that the household remains an important site of SARS-CoV-2 transmission, and recent studies have higher household SAR estimates compared with the earliest reports. More transmissible variants and vaccines may be associated with further changes.

High household transmission of SARS-CoV-2 in the United States: living density, viral load, and disproportionate impact on communities of color

Abstract: BackgroundFew prospective studies of SARS-CoV-2 transmission within households have been reported from the United States, where COVID-19 cases are the highest in the world and the pandemic has had disproportionate impact on communities of color. Methods and FindingsThis is a prospective observational study. Between April-October 2020, the UNC CO-HOST study enrolled 102 COVID-positive persons and 213 of their household members across the Piedmont region of North Carolina, including 45% who identified as Hispanic/Latinx or non-white. Households were enrolled a median of 6 days from onset of symptoms in the index case. Secondary cases within the household were detected either by PCR of a nasopharyngeal (NP) swab on study day 1 and weekly nasal swabs (days 7, 14, 21) thereafter, or based on seroconversion by day 28. After excluding household contacts exposed at the same time as the index case, the secondary attack rate (SAR) among susceptible household contacts was 60% (106/176, 95% CI 53%-67%). The majority of secondary cases were already infected at study enrollment (73/106), while 33 were observed during study follow-up. Despite the potential for continuous exposure and sequential transmission over time, 93% (84/90, 95% CI 86%-97%) of PCR-positive secondary cases were detected within 14 days of symptom onset in the index case, while 83% were detected within 10 days. Index cases with high NP viral load (>10^6 viral copies/ul) at enrollment were more likely to transmit virus to household contacts during the study (OR 4.9, 95% CI 1.3-18 p=0.02). Furthermore, NP viral load was correlated within families (ICC=0.44, 95% CI 0.26-0.60), meaning persons in the same household were more likely to have similar viral loads, suggesting an inoculum effect. High household living density was associated with a higher risk of secondary household transmission (OR 5.8, 95% CI 1.3-55) for households with >3 persons occupying <6 rooms (SAR=91%, 95% CI 71-98%). Index cases who self-identified as Hispanic/Latinx or non-white were more likely to experience a high living density and transmit virus to a household member, translating into an SAR in minority households of 70%, versus 52% in white households (p=0.05). ConclusionsSARS-CoV-2 transmits early and often among household members. Risk for spread and subsequent disease is elevated in high-inoculum households with limited living space. Very high infection rates due to household crowding likely contribute to the increased incidence of SARS-CoV-2 infection and morbidity observed among racial and ethnic minorities in the US. Quarantine for 14 days from symptom onset of the first case in the household is appropriate to prevent onward transmission from the household. Ultimately, primary prevention through equitable distribution of effective vaccines is of paramount importance. AUTHORS SUMMARYO_ST_ABSWhy was this study done?C_ST_ABSO_LIUnderstanding the secondary attack rate and the timing of transmission of SARS-CoV-2 within households is important to determine the role of household transmission in the larger pandemic and to guide public health policies about quarantine. C_LIO_LIProspective studies looking at the determinants of household transmission are sparse, particularly studies including substantial racial and ethnic minorities in the United States and studies with adequate follow-up to detect sequential transmission events. C_LIO_LIIdentifying individuals at high risk of transmitting and acquiring SARS-CoV-2 will inform strategies for reducing transmission in the household, or reducing disease in those exposed. C_LI What did the researchers do and find?O_LIBetween April-November 2020, the UNC CO-HOST study enrolled 102 households across the Piedmont region of North Carolina, including 45% with an index case who identified as racial or ethnic minorities. C_LIO_LIOverall secondary attack rate was 60% with two-thirds of cases already infected at study enrollment. C_LIO_LIDespite the potential for sequential transmission in the household, the majority of secondary cases were detected within 10 days of symptom onset of the index case. C_LIO_LIViral loads were correlated within families, suggesting an inoculum effect. C_LIO_LIHigh viral load in the index case was associated with a greater likelihood of household transmission. C_LIO_LISpouses/partners of the COVID-positive index case and household members with obesity were at higher risk of becoming infected. C_LIO_LIHigh household living density contributed to an increased risk of household transmission. C_LIO_LIRacial/ethnic minorities had an increased risk of acquiring SARS-CoV-2 in their households in comparison to members of the majority (white) racial group. C_LI What do these findings mean?O_LIHousehold transmission often occurs quickly after a household member is infected. C_LIO_LIHigh viral load increases the risk of transmission. C_LIO_LIHigh viral load cases cluster within households - suggesting high viral inoculum in the index case may put the whole household at risk for more severe disease. C_LIO_LIIncreased household density may promote transmission within racial and ethnic minority households. C_LIO_LIEarly at-home point-of-care testing, and ultimately vaccination, is necessary to effectively decrease household transmission. C_LI