scholarly journals Secondary attack rate of COVID-19 in household contacts: a systematic review

QJM ◽  
2020 ◽  
Vol 113 (12) ◽  
pp. 841-850 ◽  
Author(s):  
K Shah ◽  
D Saxena ◽  
D Mavalankar
Keyword(s):  
Systematic Review ◽  
Attack Rate ◽  
Evidence Synthesis ◽  
Geographic Location ◽  
Critical Factor ◽  
Transmission Probability ◽  
Contact Tracing ◽  
Secondary Transmission ◽  
Household Contacts ◽  
Household Transmission

Summary Coronavirus disease 2019 (COVID-19) is a novel virus with continuously evolving transmission trends. Contact tracing and quarantining of positive cases are chief strategies of disease control that has been accepted globally, though scientific knowledge regarding household transmission of the COVID-19 through contact of positive case is sparse. Current systematic review was planned to assess global statistics and characteristics of household secondary attack rate (SAR) of COVID-19. Eligible articles were retrieved through search of—MEDLINE, SCOPUS and EMBASE for the period December 2019 to 15 June 2020. Search terms were developed to identify articles reporting household SARs in various countries. After initial screening of 326 articles, 13 eligible studies were included in the final evidence synthesis. We found that SAR varies widely across countries with lowest reported rate as 4.6% and highest as 49.56%. The rates were unaffected by confounders such as population of the country, lockdown status and geographic location. Review suggested greater vulnerability of spouse and elderly population for secondary transmission than other household members. It was also observed that quarantining and isolation are most effective strategies for prevention of the secondary transmission of the disease. Symptomatic status of the index case emerged to be a critical factor, with very low transmission probability during asymptomatic phase. Present review findings recommend that adequate measures should be provided to protect the vulnerable population as only case tracing and quarantining might be insufficient. It should be combined with advisory for limiting household contacts and active surveillance for symptom onset.

scholarly journals Secondary Attack Rate of COVID-19 in Non-Household Contacts - A Systematic Review of Global Studies

2020 ◽  
Vol 52 (04) ◽  
pp. 97-107
Author(s):  
Komal Shah ◽  
Keyword(s):  
Systematic Review ◽  
Health Care ◽  
Attack Rate ◽  
Global Studies ◽  
Household Contacts ◽  
Care Workers ◽  
Prolonged Contact ◽  
Data Gaps ◽  
Casual Contact ◽  
Close Family

Objective: Secondary Attack Rate (SAR) of COVID-19 varies across various populations. We aim to assess global articles reporting SAR in non-household contacts of COVID-19 patients through systematic review approach. Methods: Four databases - MEDLINE, SCOPUS, Google Scholar and EMBASE were systematically searched for retrieval of articles reporting SAR of COVID-19 in various contacts. Initial search provided 436 articles, which through series of evaluation finally yielded 14 articles. Result: Findings suggested that SAR in various contacts varies widely. Substantial number of studies (50%) were from China; however, the two largest studies were from India. Irrespective of type of contacts, overall SAR ranged from 0.55-6%. Highest risk was found from non-household close (family, friends) contacts (2.2-22.31%) followed by casual contact (travel, meal and health-care contacts). In spite of prolonged contact with the patients, SAR was lowest in health-care workers (0-7.3%). Review highlighted that the included studies were suffering from limitations of missing data and continuously evolving operational guidelines. Conclusion: The review showed that studies furnishing SAR data in non-household contacts are limited in number and exact mode of transmission is yet not clear. Six-percent of overall SAR indicates that though the disease is infectious in nature and proper precautions must be taken, not everybody that comes in contact with the index case is infected. However, with greater risk in non-household close contacts, it is important to identify vulnerable population and implement effective preventive strategies in them. Review also indicated serious data gaps in the published literature and stipulated need of more global studies.

scholarly journals Effectiveness of vaccinating household contacts in addition to chemoprophylaxis after a case of meningococcal disease: a systematic review

2008 ◽  
Vol 136 (11) ◽  
pp. 1441-1447 ◽  
Author(s):  
M. R. HOEK ◽  
H. CHRISTENSEN ◽  
W. HELLENBRAND ◽  
P. STEFANOFF ◽  
M. HOWITZ ◽  
...  
Keyword(s):  
Systematic Review ◽  
Meningococcal Disease ◽  
Attack Rate ◽  
Meta Analysis ◽  
Weighted Average ◽  
Inclusion Criteria ◽  
Primary Case ◽  
Household Contacts ◽  
Unpublished Report

SUMMARYWe performed a systematic review to estimate the effectiveness of vaccination, in addition to chemoprophylaxis, in preventing meningococcal disease among household contacts. Medline, EMBASE, EMGM, and EUIBIS were used for data collection. Studies reporting on at least 100 primary cases and on subsequent cases in household settings with follow-up of more than 2 weeks after onset of disease in the primary case were reviewed. A meta-analysis was used to calculate the average attack rate in household contacts given chemoprophylaxis 14–365 days after onset of disease in the primary case. In total, 652 studies were identified, five studies and one unpublished report met the inclusion criteria. The weighted average attack rate was 1·1/1000 household contacts (95% CI 0·7–1·7). This review supports vaccination of household contacts in addition to chemoprophylaxis to reduce the risk of meningococcal disease among household contacts of a case caused by a vaccine-preventable serogroup.

scholarly journals Role of children in household transmission of COVID-19

2020 ◽  
pp. archdischild-2020-319910 ◽  
Author(s):  
Jieun Kim ◽  
Young June Choe ◽  
Jin Lee ◽  
Young Joon Park ◽  
Ok Park ◽  
...  
Keyword(s):  
Attack Rate ◽  
Index Case ◽  
Clinical Findings ◽  
International Travel ◽  
Contact Tracing ◽  
Secondary Case ◽  
Household Transmission ◽  
Household Members ◽  
Index Cases

ObjectiveTransmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19.Design and settingAll paediatric COVID-19 index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed. The secondary attack rate (SAR) from child index case to household secondary case was calculated. Epidemiological and clinical findings of child index case-household secondary case pair was assessed.ResultsA total of 107 paediatric COVID-19 index cases and 248 of their household members were identified. One pair of paediatric index-secondary household case was identified, giving a household SAR of 0.5% (95% CI 0.0% to 2.6%). The index case was self-quarantined at home after international travel, stayed in her room, but shared a meal table with the secondary case.ConclusionThe SAR from children to household members was low in the setting of social distancing, underscoring the importance of rigorous contact tracing and early isolation in limiting transmission within households.

scholarly journals Secondary transmission of SARS-CoV-2 in educational settings in Northern Italy from September 2020 to April 2021: a population-based study

2021 ◽  
Author(s):  
Olivera Djuric ◽  
Elisabetta Larosa ◽  
Mariateresa Cassinadri ◽  
Silvia Cilloni ◽  
Eufemia Bisaccia ◽  
...  
Keyword(s):  
Attack Rate ◽  
Index Case ◽  
School Setting ◽  
Population Based ◽  
Contact Tracing ◽  
Secondary Case ◽  
Secondary Transmission ◽  
Source Of Infection ◽  
Alpha Variant ◽  
Type Of School

Background: We aimed to quantify the risk of transmission of SARS-CoV-2 in the school setting by type of school, characteristics of the index case and calendar period in the Reggio Emilia province (RE), Italy, from school reopening in September 2020 until the beginning of April 2021. The secondary aim was to estimate the promptness of contact tracing. Methods: A population-based analysis of surveillance data of all COVID-19 cases occurring in RE, Italy, from September 1, 2020, to April 4th, 2021, for which a school contact and/or exposure was suspected. Indicator of the delay in contact tracing was computed as the time elapsed since positivity of the index case and the date on which the swab for classmates was scheduled (or most were scheduled). Results: Overall, 30,426 and 13,571 contacts among classmates and teachers/staff, respectively, were identified and received recommendation for testing; 43,414 (98.7%) performed the test. Secondary transmission occurred in about 40% of the investigated classes, and the overall secondary case attack rate was 4%, slightly higher when the index case was a teacher, but with almost no differences by type of school and stable during the study period. Promptness of contact tracing increased during the study period, reducing the time from index case identification and testing of contacts from 7 to 3 days, as well the ability to identify possible source of infection in the index case (from 42% in September/October, to 22% in November, to 50% in December-April). Conclusions: Despite the spread of the Alpha variant during the study period in RE, the secondary case attack rate remained stable from school reopening in September 2020 until the beginning of April 2021.

scholarly journals What do we know about SARS-CoV-2 transmission? A systematic review and meta-analysis of the secondary attack rate, serial interval, and asymptomatic infection

2020 ◽  
Author(s):  
Wee Chian Koh ◽  
Lin Naing ◽  
Muhammad Ali Rosledzana ◽  
Mohammad Fathi Alikhan ◽  
Liling Chaw ◽  
...  
Keyword(s):  
Systematic Review ◽  
Attack Rate ◽  
Meta Analysis ◽  
Original Data ◽  
Asymptomatic Infection ◽  
Control Measures ◽  
Transmission Risk ◽  
Contact Tracing ◽  
Random Effects Models ◽  
Serial Interval

Background Current SARS-CoV-2 containment measures rely on the capacity to control person-to-person viral transmission. Effective prioritization of these measures can be determined by understanding SARS-CoV-2 transmission dynamics. We conducted a systematic review and meta-analyses of three parameters: (i) secondary attack rate (SAR) in various settings, (ii) clinical onset serial interval (SI), and (iii) the proportion of asymptomatic infection. Methods and Findings We searched PubMed, medRxiv, and bioRxiv databases between January 1, 2020, and May 15, 2020, for articles describing SARS-CoV-2 attack rate, SI, and asymptomatic infection. Studies were included if they presented original data for estimating point estimates and 95% confidence intervals of the three parameters. Random effects models were constructed to pool SAR, mean SI, and asymptomatic proportion. Risk ratios were used to examine differences in transmission risk by setting, type of contact, and symptom status of the index case. Publication and related bias were assessed by funnel plots and Egger's meta-regression test for small-study effects. Our search strategy for SAR, SI, and asymptomatic infection identified 459, 572, and 1624 studies respectively. Of these, 20 studies met the inclusion criteria for SAR, 18 studies for SI, and 66 studies for asymptomatic infection. We estimated the pooled household SAR at 15.4% (95% CI: 12.2%, 18.7%) compared to 4.0% (95% CI: 2.8%, 5.2%) in non-household settings. We observed variation across settings; however, the small number of studies limited power to detect associations and sources of heterogeneity. SAR of symptomatic index cases is significantly higher than cases that were symptom-free at diagnosis (RR 2.55, 95% CI: 1.47, 4.45). Adults appear to be more susceptible to transmission than children (RR 1.40, 95% CI: 1.00, 1.96). The pooled mean SI is estimated at 4.87 days (95% CI: 3.98, 5.77). The pooled proportion of cases who had no symptoms at diagnosis is 25.9% (95% CI: 18.8%, 33.1%). Conclusions Based our pooled estimates, 10 infected symptomatic persons living with 100 contacts would result in 15 additional cases in <5 days. To be effective, quarantine of contacts should occur within 3 days of symptom onset. If testing and tracing relies on symptoms, one-quarter of cases would be missed. As such, while aggressive contact tracing strategies may be appropriate early in an outbreak, as it progresses, control measures should transition to account for SAR variability across settings. Targeted strategies focusing on high-density enclosed settings may be effective without overly restricting social movement.

scholarly journals Estimating Household Transmission of SARS-CoV-2

2020 ◽  
Author(s):  
Mihaela Curmei ◽  
Andrew Ilyas ◽  
Owain Evans ◽  
Jacob Steinhardt
Keyword(s):  
Attack Rate ◽  
False Negative ◽  
Policy Implications ◽  
Contact Tracing ◽  
Reliable Estimate ◽  
False Negatives ◽  
Social Distancing ◽  
Household Transmission ◽  
Contact Patterns ◽  
Community Transmission

Introduction and GoalsSARS-CoV-2 is transmitted both in the community and within households. Social distancing and lockdowns reduce community transmission but do not directly address household transmission. We provide quantitative measures of household transmission based on empirical data, and estimate the contribution of households to overall spread. We highlight policy implications from our analysis of household transmission, and more generally, of changes in contact patterns under social distancing.MethodsWe investigate the household secondary attack rate (SAR) for SARS-CoV-2, as well as Rh, which is the average number of within-household infections caused by a single index case. We identify previous works that estimated the SAR. We correct these estimates based on the false-negative rate of PCR testing and the failure to test asymptomatics. Results are pooled by a hierarchical Bayesian random-effects model to provide a meta-analysis estimate of the SAR. We estimate Rh using results from population testing in Vo’, Italy and contact tracing data that we curate from Singapore. The code and data behind our analysis are publicly available1.ResultsWe identified nine studies of the household secondary attack rate. Our modeling suggests the SAR is heterogeneous across studies. The pooled central estimate of the SAR is 30% but with a posterior 95% credible interval of (0%, 67%) reflecting this heterogeneity. This corresponds to a posterior mean for the SAR of 30% (18%, 43%) and a standard deviation of 15% (9%, 27%). If results are not corrected for false negatives and asymptomatics, the pooled central estimate for the SAR is 20% (0%, 43%). From the same nine studies, we estimate Rh to be 0.47 (0.13, 0.77). Using contact tracing data from Singapore, we infer an Rh value of 0.32 (0.22, 0.42). Population testing data from Vo’ yields an Rh estimate of 0.37 (0.34, 0.40) after correcting for false negatives and asymptomatics.InterpretationOur estimates of Rh suggest that household transmission was a small fraction (5%-35%) of R before social distancing but a large fraction after (30%-55%). This suggests that household transmission may be an effective target for interventions. A remaining uncertainty is whether household infections actually contribute to further community transmission or are contained within households. This can be estimated given high-quality contact tracing data.More broadly, our study points to emerging contact patterns (i.e., increased time at home relative to the community) playing a role in transmission of SARS-CoV-2. We briefly highlight another instance of this phenomenon (differences in contact between essential workers and the rest of the population), provide coarse estimates of its effect on transmission, and discuss how future data could enable a more reliable estimate.

scholarly journals Characteristics of Household Transmission of COVID-19

2020 ◽  
Vol 71 (8) ◽  
pp. 1943-1946 ◽  
Author(s):  
Wei Li ◽  
Bo Zhang ◽  
Jianhua Lu ◽  
Shihua Liu ◽  
Zhiqiang Chang ◽  
...  
Keyword(s):  
Risk Factors ◽  
Attack Rate ◽  
Rt Pcr ◽  
Spousal Relationship ◽  
Telephone Interviews ◽  
Household Contacts ◽  
Household Transmission ◽  
Household Members ◽  
Baseline Characteristics ◽  
Index Cases

Abstract Background Since December 2019, SARS-CoV-2 has extended to most parts of China with &gt;80 000 cases and to at least 100 countries with &gt;60 000 international cases as of 15 March 2020. Here we used a household cohort study to determine the features of household transmission of COVID-19. Methods A total of 105 index patients and 392 household contacts were enrolled. Both index patients and household members were tested by SARS-CoV-2 RT-PCR. Information on all recruited individuals was extracted from medical records and confirmed or supplemented by telephone interviews. The baseline characteristics of index cases and contact patients were described. Secondary attack rates of SARS-CoV-2 to contact members were computed and the risk factors for transmission within the household were estimated. Results Secondary transmission of SARS-CoV-2 developed in 64 of 392 household contacts (16.3%). The secondary attack rate to children was 4% compared with 17.1% for adults. The secondary attack rate to the contacts within the households with index patients quarantined by themselves since onset of symptoms was 0% compared with 16.9% for contacts without quarantined index patients. The secondary attack rate to contacts who were spouses of index cases was 27.8% compared with 17.3% for other adult members in the households. Conclusions The secondary attack rate of SARS-CoV-2 in household is 16.3%. Age of household contacts and spousal relationship to the index case are risk factors for transmission of SARS-CoV-2 within a household. Quarantine of index patients at home since onset of symptoms is useful to prevent the transmission of SARS-Co-2 within a household.

scholarly journals Epidemiology of COVID-19 in Northern Ireland, 26 February 2020–26 April 2020

2021 ◽  
Vol 149 ◽  
Author(s):  
J. Pett ◽  
P. McAleavey ◽  
P. McGurnaghan ◽  
R. Spiers ◽  
M. O'Doherty ◽  
...  
Keyword(s):  
Northern Ireland ◽  
Contact Tracing ◽  
Risk Of Infection ◽  
Household Contacts ◽  
Household Transmission ◽  
Effective Interventions ◽  
Incidence And Mortality ◽  
Testing Data ◽  
The Republic ◽  
The Uk

Abstract This paper describes the epidemiology of coronavirus disease 2019 (COVID-19) in Northern Ireland (NI) between 26 February 2020 and 26 April 2020, and analyses enhanced surveillance and contact tracing data collected between 26 February 2020 and 13 March 2020 to estimate secondary attack rates (SAR) and relative risk of infection among different categories of contacts of individuals with laboratory confirmed severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. Our results show that during the study period COVID-19 cumulative incidence and mortality was lower in NI than the rest of the UK. Incidence and mortality were also lower than in the Republic of Ireland (ROI), although these observed differences are difficult to interpret given considerable differences in testing and surveillance between the two nations. SAR among household contacts was 15.9% (95% CI 6.6%–30.1%), over 6 times higher than the SAR among ‘high-risk’ contacts at 2.5% (95% CI 0.9%–5.4%). The results from logistic regression analysis of testing data on contacts of laboratory-confirmed cases show that household contacts had 11.0 times higher odds (aOR: 11.0, 95% CI 1.7–70.03, P-value: 0.011) of testing positive for SARS-CoV-2 compared to other categories of contacts. These results demonstrate the importance of the household as a locus of SARS-CoV-2 transmission, and the urgency of identifying effective interventions to reduce household transmission.

scholarly journals The Household Secondary Attack Rate of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Rapid Review

2020 ◽  
Author(s):  
Hannah F Fung ◽  
Leonardo Martinez ◽  
Fernando Alarid-Escudero ◽  
Joshua A Salomon ◽  
David M Studdert ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Random Effects ◽  
Attack Rate ◽  
Control Strategies ◽  
Rapid Review ◽  
The Public ◽  
Household Contacts ◽  
Household Transmission ◽  
Testing Frequency

Abstract Background Although much of the public health effort to combat coronavirus disease 2019 (COVID-19) has focused on disease control strategies in public settings, transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within households remains an important problem. The nature and determinants of household transmission are poorly understood. Methods To address this gap, we gathered and analyzed data from 22 published and prepublished studies from 10 countries (20 291 household contacts) that were available through 2 September 2020. Our goal was to combine estimates of the SARS-CoV-2 household secondary attack rate (SAR) and to explore variation in estimates of the household SAR. Results The overall pooled random-effects estimate of the household SAR was 17.1% (95% confidence interval [CI], 13.7–21.2%). In study-level, random-effects meta-regressions stratified by testing frequency (1 test, 2 tests, &gt;2 tests), SAR estimates were 9.2% (95% CI, 6.7–12.3%), 17.5% (95% CI, 13.9–21.8%), and 21.3% (95% CI, 13.8–31.3%), respectively. Household SARs tended to be higher among older adult contacts and among contacts of symptomatic cases. Conclusions These findings suggest that SARs reported using a single follow-up test may be underestimated, and that testing household contacts of COVID-19 cases on multiple occasions may increase the yield for identifying secondary cases.

scholarly journals A meta-analysis on the role of children in SARS-CoV-2 in household transmission clusters

2020 ◽  
Author(s):  
Yanshan Zhu ◽  
Conor J Bloxham ◽  
Katina D Hulme ◽  
Jane E Sinclair ◽  
Zhen Wei Marcus Tong ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Risk Ratio ◽  
Attack Rate ◽  
Index Case ◽  
Meta Analysis ◽  
Household Contacts ◽  
Household Transmission ◽  
Potential Vaccine ◽  
Index Cases

Abstract The role of children in the spread of SARS-CoV-2 remains highly controversial. To address this issue, we performed a meta-analysis of the published literature on household SARS-CoV-2 transmission clusters (n=213 from 12 countries). Only 8 (3.8%) transmission clusters were identified as having a paediatric index case. Asymptomatic index cases were associated with a lower secondary attack in contacts than symptomatic index cases (estimate risk ratio [RR], 0.17; 95% confidence interval [CI], 0.09-0.29). To determine the susceptibility of children to household infections the secondary attack rate (SAR) in paediatric household contacts was assessed. The secondary attack rate in paediatric household contacts was lower than in adult household contacts (RR, 0.62; 95% CI, 0.42-0.91). These data have important implications for the ongoing management of the COVID-19 pandemic, including potential vaccine prioritization strategies.

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