scholarly journals Digital proximity tracing app notifications lead to faster quarantine in non-household contacts: results from the Zurich SARS-CoV-2 Cohort Study

2020 ◽  
Author(s):  
Tala Ballouz ◽  
Dominik Menges ◽  
Helene E Aschmann ◽  
Anja Domenghino ◽  
Jan S Fehr ◽  
...  
Keyword(s):  
Cohort Study ◽  
Population Based ◽  
Contact Tracing ◽  
Household Contacts ◽  
Health Directorate ◽  
Multivariable Analyses ◽  
University Of Zurich ◽  
Exposure Setting ◽  
Index Cases ◽  
Close Contacts

AbstractBackgroundDigital proximity tracing (DPT) apps may warn exposed individuals faster than manual contact tracing (MCT), leading to earlier interruption of transmission chains through quarantine. However, it is yet unclear whether these apps lead to a reduction in transmissions under real-world conditions. This study aimed at evaluating whether the SwissCovid DPT app is effective in warning close contacts of SARS-CoV-2 infected cases and prompting them to quarantine earlier.MethodsA population-based sample of adult index cases and close contacts identified through MCT and enrolled in the Zurich SARS-CoV-2 Cohort study were surveyed regarding use of the SwissCovid app and SARS-CoV-2 exposure setting. We analyzed ooutcomes related to app effectiveness and adherence (i.e., receipt and uploading of notification codes by index cases; receipt of app warnings and steps taken by close contacts). Furthermore, we performed adjusted time-to-event analyses stratified by exposure setting to estimate the effect of the app on time between relevant exposure and entering quarantine among close contacts.FindingsWe included 393 index cases and 261 close contacts in the analysis. Among index cases using SwissCovid, 88% reported receiving and uploading a notification code in the app to trigger a warning among proximity contacts. Among close contacts using the app, 38% reported receiving an app warning due to the risk exposure. We found that non-household contacts who were notified by the app started quarantine at a median of 2 days after exposure, while those not notified started quarantine at a median of 3 days. In stratified multivariable analyses, app notified contacts had a greater probability of going into quarantine earlier than those without app notification (HR 1·53, 95% CI 1·15-2·03).InterpretationOur study showed that non-household contacts notified by the app started quarantine one day earlier than those not notified by the app. These findings constitute the first evidence that DPT may reach exposed contacts faster than MCT, leading to earlier quarantine and potential interruption of SARS-CoV-2 transmission chains.FundingCantonal Health Directorate Zurich, University of Zurich Foundation and the Swiss Federal Office of Public Health.

scholarly journals Adherence and Association of Digital Proximity Tracing App Notifications With Earlier Time to Quarantine: Results From the Zurich SARS-CoV-2 Cohort Study

2021 ◽  
Vol 66 ◽  
Author(s):  
Tala Ballouz ◽  
Dominik Menges ◽  
Hélène E. Aschmann ◽  
Anja Domenghino ◽  
Jan S. Fehr ◽  
...  
Keyword(s):  
Cohort Study ◽  
Population Based ◽  
Contact Tracing ◽  
Time To Event ◽  
Household Contacts ◽  
Close Contacts

Objectives: We aimed to evaluate the effectiveness of the SwissCovid digital proximity tracing (DPT) app in notifying exposed individuals and prompting them to quarantine earlier compared to individuals notified only by manual contact tracing (MCT).Methods: A population-based sample of cases and close contacts from the Zurich SARS-CoV-2 Cohort was surveyed regarding SwissCovid app use and SARS-CoV-2 exposure. We descriptively analyzed app adherence and effectiveness, and evaluated its effects on the time between exposure and quarantine among contacts using stratified multivariable time-to-event analyses.Results: We included 393 SARS-CoV-2 infected cases and 261 close contacts. 62% of cases reported using SwissCovid and among those, 88% received and uploaded a notification code. 71% of close contacts were app users, of which 38% received a warning. Non-household contacts notified by SwissCovid started quarantine 1 day earlier and were more likely to quarantine earlier than those not warned by the app (HR 1.53, 95% CI 1.15–2.03).Conclusion: These findings provide evidence that DPT may reach exposed contacts faster than MCT, with earlier quarantine and potential interruption of SARS-CoV-2 transmission chains.

scholarly journals Vaccine effectiveness against SARS-CoV-2 transmission and infections among household and other close contacts of confirmed cases, the Netherlands, February to May 2021

2021 ◽  
Vol 26 (31) ◽  
Author(s):  
Brechje de Gier ◽  
Stijn Andeweg ◽  
Rosa Joosten ◽  
Ronald ter Schegget ◽  
Naomi Smorenburg ◽  
...  
Keyword(s):  
The Netherlands ◽  
Confidence Interval ◽  
Attack Rate ◽  
Severe Disease ◽  
Vaccine Effectiveness ◽  
Monitoring Data ◽  
High Effectiveness ◽  
Household Contacts ◽  
Index Cases ◽  
Close Contacts

Several studies report high effectiveness of COVID-19 vaccines against SARS-CoV-2 infection and severe disease, however an important knowledge gap is the vaccine effectiveness against transmission (VET). We present estimates of the VET to household and other close contacts in the Netherlands, from February to May 2021, using contact monitoring data. The secondary attack rate among household contacts was lower for fully vaccinated than unvaccinated index cases (11% vs 31%), with an adjusted VET of 71% (95% confidence interval: 63–77).

scholarly journals Yield of Systematic Longitudinal Screening of Household Contacts of Pre-Extensively Drug Resistant (PreXDR) and Extensively Drug Resistant (XDR) Tuberculosis Patients in Mumbai, India

2020 ◽  
Vol 5 (2) ◽  
pp. 83
Author(s):  
Roma Haresh Paryani ◽  
Vivek Gupta ◽  
Pramila Singh ◽  
Madhur Verma ◽  
Sabira Sheikh ◽  
...  
Keyword(s):  
Contact Tracing ◽  
Drug Resistant ◽  
Household Contacts ◽  
Tb Treatment ◽  
Extensively Drug Resistant ◽  
High Incidence ◽  
Resistance Patterns ◽  
One Year ◽  
Index Cases

While risk of tuberculosis (TB) is high among household contacts (HHCs) of pre-extensively drug resistant (pre-XDR) TB and XDR-TB, data on yield of systematic longitudinal screening are lacking. We aim to describe the yield of systematic longitudinal TB contact tracing among HHCs of patients with pre-XDR-TB and XDR-TB. At the Médecins Sans Frontières (MSF) clinic, Mumbai, India a cohort comprising 518 HHCs of 109 pre-XDR and XDR index cases was enrolled between January 2016 and June 2018. Regular HHC follow-ups were done till one year post treatment of index cases. Of 518 HHCs, 23 had TB (21 on TB treatment and two newly diagnosed) at the time of first visit. Of the rest, 19% HHCs had no follow-ups. Fourteen (3.5%) TB cases were identified among 400 HHCs; incidence rate: 2072/100,000 person-years (95% CI: 1227–3499). The overall yield of household contact tracing was 3% (16/518). Of 14 who were diagnosed with TB during follow-up, six had drug susceptible TB (DSTB); six had pre-XDR-TB and one had XDR-TB. Five of fourteen cases had resistance patterns concordant with their index case. In view of the high incidence of TB among HHCs of pre-XDR and XDR-TB cases, follow-up of HHCs for at least the duration of index cases’ treatment should be considered.

scholarly journals Is the risk of cervical atypia associated with the interval between menarche and the start of sexual activity? A population-based cohort study

BMJ Open ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. e030091 ◽  
Author(s):  
Indira Adhikari ◽  
Tiina Eriksson ◽  
Tapio Luostarinen ◽  
Dan Apter ◽  
Matti Lehtinen
Keyword(s):  
Cohort Study ◽  
Sexual Activity ◽  
Short Interval ◽  
Population Based ◽  
Hpv 16 ◽  
Increased Risk ◽  
Registration Number ◽  
Multivariable Analyses ◽  
Age Range

ObjectiveWe investigated whether the risk of cervical atypia is associated with a short interval between the age at first sexual intercourse (FSI) or age at the start of oral contraceptive (OC) use and menarche.DesignA population-based cohort study.SettingFinnish women in the age range of 16–17 years old were enrolled in the PATRICIA trial of human papillomavirus (HPV) 16/18 vaccine efficacy.ParticipantsThe association of cervical atypia with the interval between FSI or start of OC use and menarche was assessed in the control arm (hepatitis A vaccinated) who had participated in biannual clinical follow-up visits for 4 years. Altogether, 913 women had normal baseline cervical cytology and answered behavioural questionnaires at enrolment and end of the follow-up.Main outcome measureORs with 95% CIs using univariate and multivariable logistic regression were used to assess the association between cervical atypia and the interval between FSI or the start of OC use and menarche.ResultsThe mean ages at menarche, FSI and the start of OC use were 12.4, 16.0 and 16.4.Chlamydiatrachomatisinfection was associated with an increased risk of cervical atypia in women with a short (<3 years) interval between menarche and FSI/start of OC use (OR 1.8, 95% CI 1.0 to 3.6 and OR 2.2, 95% CI 1.0 to 5.1). Whereas HPV 16/18 infection was associated with increased atypia risk estimates in women with a longer (≥3 years) interval (OR 1.8, 95% CI 1.1 to 2.7 and OR 1.4, 95% CI 1.0 to 2.1). In women with a short interval between menarche and FSI, early age at the start of OC use was not associated with an increased risk of cervical atypia in the univariate (OR 0.7) nor multivariable analyses.ConclusionShort interval between menarche and the age at start of sexual activity does not increase the risk of HPV-associated cervical atypia.Trial registration numberNCT00122681.

The first 2 months of COVID-19 contact tracing in the Northern Territory of Australia, March–April 2020

2020 ◽  
Vol 44 ◽  
Author(s):  
Anthony DK Draper ◽  
Karen E Dempsey ◽  
Rowena H Boyd ◽  
Emma M Childs ◽  
Hayley M Black ◽  
...  
Keyword(s):  
Disease Control ◽  
Healthcare Workers ◽  
Northern Territory ◽  
Contact Tracing ◽  
Cruise Ship ◽  
Disease Symptoms ◽  
Household Contacts ◽  
Close Contacts

The Northern Territory (NT) Centre for Disease Control (CDC) undertook contact tracing of all notified cases of coronavirus disease 2019 (COVID-19) within the Territory. There were 28 cases of COVID-19 notified in the NT between 1 March and 30 April 2020. In total 527 people were identified as close contacts over the same period; 493 were successfully contacted; 445 were located in the NT and were subsequently quarantined and monitored for disease symptoms daily for 14 days after contact with a confirmed COVID-19 case. Of these 445 close contacts, 4 tested positive for COVID-19 after developing symptoms; 2/46 contacts who were cruise ship passengers (4.3%, 95% CI 0.5–14.8%) and 2/51 household contacts (3.9%, 95% CI 0.5–13.5%). None of the 326 aircraft passengers or 4 healthcare workers who were being monitored in the NT as close contacts became cases.

scholarly journals A comparison of COVID-19 secondary attack rate in household and close contacts compared to current risk stratification guidelines of the Kerala government

2021 ◽  
pp. 004947552110020
Author(s):  
Balram Rathish ◽  
Arun Wilson ◽  
Sonya Joy
Keyword(s):  
High Risk ◽  
Risk Stratification ◽  
Attack Rate ◽  
Low Risk ◽  
Contact Tracing ◽  
Index Cases ◽  
Current Risk ◽  
Close Contacts

COVID-19 has been found to be highly infectious with a high secondary attack rate with a R0 of 3.3. However, the secondary attack rate based on risk stratification is sparsely reported, if ever. We studied the contact tracing data for two index cases of COVID-19 with some overlap of contacts. We found that 60% of high-risk contacts and 0% of low-risk contacts of symptomatic COVID-19 patients contracted the infection, in keeping with the Kerala government contact risk stratification guidelines.

scholarly journals The clinical spectrum of COVID-19: A population-based cohort study in Iceland

2020 ◽  
Author(s):  
Elias Eythorsson ◽  
Dadi Helgason ◽  
Ragnar Freyr Ingvarsson ◽  
Helgi K Bjornsson ◽  
Lovisa Bjork Olafsdottir ◽  
...  
Keyword(s):  
Cohort Study ◽  
Diagnostic Testing ◽  
Population Based ◽  
Case Definition ◽  
Clinical Spectrum ◽  
World Health ◽  
Contact Tracing ◽  
Case Definitions ◽  
Presenting Symptoms ◽  
Health Organization

Background: Previous studies on the epidemiology and clinical characteristics of COVID-19 have generally been limited to hospitalized patients. The aim of this study was to describe the complete clinical spectrum of COVID-19, based on a nationwide cohort with extensive diagnostic testing and a rigorous contact tracing approach. Methods: A population-based cohort study examining symptom progression using prospectively recorded data on all individuals with a positive test (RT-PCR) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who were enrolled in a telehealth monitoring service provided to all identified cases in Iceland. Symptoms were systematically monitored from diagnosis to recovery. Results: From January 31 to April 30, 2020, a total of 45,105 individuals (12% of the Icelandic population) were tested for SARS-CoV-2, of whom 1797 were positive, yielding a population incidence of 5 per 1000 individuals. The most common presenting symptoms were myalgia (55%), headache (51%), and non-productive cough (49%). At the time of diagnosis, 5.3% of cases reported no symptoms and 3.1% remained asymptomatic during follow-up. In addition, 216 patients (13.8%) and 349 patients (22.3%) did not meet the case definition of the Centers for Disease Control and Prevention and the World Health Organization, respectively. The majority (67.5%) of patients had mild symptoms throughout the course of the disease. Conclusion: In the setting of broad access to diagnostic testing, the majority of SARS-CoV-2-positive patients were found to have mild symptoms. Fever and dyspnea were less common than previously reported. A substantial proportion of patients did not meet recommended case definitions at the time of diagnosis.

scholarly journals Swab and Sputum SARS-CoV-2 RNA-Negative, CT-Positive, Symptomatic Contacts of COVID-19 Cases: A Hypothesis-Generating Prospective Population-Based Cohort Study of Eight Clusters

2021 ◽  
Vol 8 ◽  
Author(s):  
Lei Huang ◽  
Xiuwen Zhang ◽  
Lingli Zhang ◽  
Jingjing Xu ◽  
Zhijian Wei ◽  
...  
Keyword(s):  
Cohort Study ◽  
Throat Swab ◽  
Population Based ◽  
Illness Onset ◽  
Ct Findings ◽  
Virus Rna ◽  
Group 3 ◽  
Group 2 ◽  
Group 1 ◽  
Close Contacts

Background: While some contacts of COVID-19 cases become symptomatic and radiographically abnormal, their SARS-CoV-2 RNA tests remain negative throughout the disease course. This prospective population-based cohort study aimed to explore their characteristics and significances.Methods: From January 22, 2020, when the first COVID-19 case was identified in Hefei, China, until July 3, a total of 14,839 people in Feidong, Hefei, with a population of ~1,081,000 underwent SARS-CoV-2 RNA testing, where 36 cases (0.2%) with confirmed COVID-19 infection (Group 1) and 27 close contacts (0.2%) testing negative for SARS-CoV-2 RNA but having both positive COVID-19 exposure histories and CT findings (Group 2) from eight clusters were prospectively identified. Another 62 non-COVID-19 pneumonia cases without any exposure history (Group 3) were enrolled, and characteristics of the three groups were described and compared. We further described a cluster with an unusual transmission pattern.Results: Fever was more common in Group 2 than Groups 1 and 3. Frequency of diarrhea in Group 1 was higher than in Groups 2 and 3. Median leucocyte, neutrophil, monocyte, and eosinophil counts were all lower in Groups 1 and 2 than in Group 3. Median D-dimer level was lower in Group 1 than in Groups 2 and 3. Total protein and albumin levels were higher in Groups 1 and 2 than in Group 3. C-reactive protein level was lower and erythrocyte sedimentation rate slower in Groups 1 and 2 than in Group 3. Combination antibacterial therapy and levofloxacin were more often used in Group 3 than in Groups 1 and 2. Lopinavir/ritonavir was more often administered in Groups 1 and 2 than in Group 3. Group 1 received more often corticosteroids than Groups 2 and 3. Group 2 received less often oxygen therapy than Groups 1 and 3. Median duration from illness onset to discharge was longer in Group 1 (27 d) than Groups 2 and 3 (both 17 d). Among contacts of a confirmed COVID-19 patient, only one had a positive virus RNA test but remained asymptomatic and had negative CT findings, and three had negative virus RNA tests but had symptoms and positive CT findings, one of whom transmitted COVID-19 to another asymptomatic laboratory-confirmed patient who had no other exposures.Conclusions: Among close contacts of confirmed COVID-19 cases, some present with positive symptoms and CT findings but test negative for SARS-CoV-2 RNA using common respiratory (throat swab and sputum) specimens; they have features more similar to confirmed COVID-19 cases than non-COVID-19 pneumonia cases and might have transmitted SARS-CoV-2 to others. Such cases might add to the complexity and difficulty of COVID-19 control. Our hypothesis-generating study might suggest that SARS-CoV-2 RNA testing by rRT-PCR assays of common respiratory (throat swab and sputum) specimens alone, the widely accepted “golden standard” for diagnosing COVID-19, might be sometimes insufficient, and that further studies with some further procedures (e.g., testing via bronchoalveolar lavage or specific antibodies) would be warranted for Group 2-like patients, namely, the SARS-CoV-2 RNA-negative (tested using common respiratory specimens), radiographically positive, symptomatic contacts of COVID-19 cases, to further reveal their nature.

scholarly journals Meningococcal carriage in close contacts of cases

1991 ◽  
Vol 106 (1) ◽  
pp. 133-141 ◽  
Author(s):  
K. A. V. Cartwright ◽  
J. M. Stuart ◽  
P. M. Robinson
Keyword(s):  
Meningococcal Disease ◽  
Close Contact ◽  
Household Contact ◽  
Nasopharyngeal Carriage ◽  
Carriage Rate ◽  
Household Contacts ◽  
South West ◽  
Deep Site ◽  
Index Cases ◽  
Close Contacts

SUMMARYBetween 1 October 1986 and 31 March 1987, 55 cases of meningococcal disease were identified in the South-West of England, an attack rate of 1·54 per 100000 during the study period. Antibiotics used in the treatment of the disease successfully eliminated nasopharyngeal carriage of meningococci in 13 out of 14 cases without use of rifampicin. The overall meningococcal carriage rate in 384 close contacts was 18·2% and the carriage rate of strains indistinguishable from the associated case strain was 11·1%. The carriage rate of indistinguishable strains in household contacts (16·0%) was higher than the carriage rate in contacts living at other addresses (7·0%, P > 0·05). A 2·day course of rifampicin successfully eradicated meningococci from 46 (98%) of 47 colonized contacts.In one third of cases groupable meningococci were isolated from at least one household contact; 92% of these isolates were of the same serogroup as the associated case strain. When a meningococcus is not isolated from a deep site in a clinical case of meningococcal disease, culture of serogroup A or C strains from nasopharyngeal swabs of the case or of household contacts is an indication that the close contact group should be offered meningococcal A + C vaccine in addition to chemoprophylaxis. The failure in this and other studies to isolate meningococci from any household contact in the majority of cases may be due either to the relative insensitivity of nasopharyngeal swabbing in detecting meningococcal carriage or to the acquisition of meningococci by most index cases from sources outside the household.

Population-based contact investigation of a cluster of tuberculosis cases in a small village

2009 ◽  
Vol 137 (10) ◽  
pp. 1426-1435 ◽  
Author(s):  
J. CASTILLA ◽  
R. PALMERA ◽  
A. NAVASCUÉS ◽  
M. ABETI ◽  
A. GUILLERMO ◽  
...  
Keyword(s):  
Latent Tuberculosis ◽  
Population Based ◽  
Restriction Pattern ◽  
Contact Tracing ◽  
Chromosomal Dna ◽  
Resident Population ◽  
Contact Investigation ◽  
Dna Restriction ◽  
Contact Investigations ◽  
Close Contacts

SUMMARYA cluster of five cases of tuberculosis (TB) in persons aged 19–23 years who were not close contacts was detected in a small village in Spain in 2006. All culture isolates had the same chromosomal-DNA restriction pattern. Contact investigations of family members, friends, workmates and schoolmates were complemented with tuberculin screening offered to the resident population born between 1976 and 1995. Expanded contact tracing detected two new cases of TB, 27 tuberculin conversions and an excess of latent tuberculosis infections (LTI) in persons born between 1978 and 1990. The contacts of two cases had a significantly elevated prevalence of LTI. Two secondary cases of TB, 33·3% of those diagnosed with LTI and 47·8% of the converters were unaware of any contact with the TB cases, but had frequented some of the same bars. This study suggests that a considerable percentage of the episodes of TB transmission in young people may escape detection in conventional contact studies.

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