Understanding the risk of infection from household- and community-exposures and the transmissibility of asymptomatic infections is critical to SARS-CoV-2 control. Limited previous evidence is based primarily on virologic testing, which disproportionately misses mild and asymptomatic infections. Serologic measures are more likely to capture all previously infected individuals. We apply household transmission models to data from a cross-sectional, household-based population serosurvey of 4,534 people ≥5 years from 2,267 households enrolled April-June 2020 in Geneva, Switzerland. We found that the risk of infection from exposure to a single infected household member aged ≥5 years (17.3%,13.7-21.7) was more than three-times that of extra-household exposures over the first pandemic wave (5.1%,4.5-5.8). Young children had a lower risk of infection from household members. Working-age adults had the highest extra-household infection risk. Seropositive asymptomatic household members had 69.4% lower odds (95%CrI,31.8-88.8%) of infecting another household member compared to those reporting symptoms, accounting for 14.5% (95%CrI, 7.2-22.7%) of all household infections.

Background Serological assays detecting anti-SARS-CoV-2 antibodies are being widely deployed in studies and clinical practice. However, the duration and effectiveness of the protection conferred by the immune response remains to be assessed in population-based samples. To estimate the incidence of newly acquired SARS-CoV-2 infections in seropositive individuals as compared to seronegative controls we conducted a retrospective longitudinal matched study. Methods A seroprevalence survey including a representative sample of the population was conducted in Geneva, Switzerland between April and June 2020, immediately after the first pandemic wave. Seropositive participants were matched one-to-two to seronegative controls, using a propensity-score including age, gender, immunodeficiency, BMI, smoking status and education level. Each individual was linked to a state-registry of SARS-CoV-2 infections. Our primary outcome was confirmed infections occurring from serological status assessment to the end of the second pandemic wave (January 2021). Results Among 8344 serosurvey participants, 498 seropositive individuals were selected and matched with 996 seronegative controls. After a mean follow-up of 35.6 (SD 3.2) weeks, 7 out of 498 (1.4%) seropositive subjects had a positive SARS-CoV-2 test, of whom 5 (1.0%) were classified as reinfections. In contrast, the infection rate was higher in seronegative individuals (15.5%, 154/996) during a similar follow-up period (mean 34.7 [SD 3.2] weeks), corresponding to a 94% (95%CI 86% to 98%, P<0.001) reduction in the hazard of having a positive SARS-CoV-2 test for seropositives. Conclusions Seroconversion after SARS-CoV-2 infection confers protection against reinfection lasting at least 8 months. These findings could help global health authorities establishing priority for vaccine allocation.

Limited data exist on SARS-CoV-2 infection rates across sectors and occupations, hindering our ability to make rational policy, including vaccination prioritization, to protect workers and limit SARS-CoV-2 spread. Here, we present results from our SEROCoV-WORK + study, a serosurvey of workers recruited after the first wave of the COVID-19 pandemic in Geneva, Switzerland. We tested workers (May 18—September 18, 2020) from 16 sectors and 32 occupations for anti-SARS-CoV-2 IgG antibodies. Of 10,513 participants, 1026 (9.8%) tested positive. The seropositivity rate ranged from 4.2% in the media sector to 14.3% in the nursing home sector. We found considerable within-sector variability: nursing home (0%–31.4%), homecare (3.9%–12.6%), healthcare (0%–23.5%), public administration (2.6%–24.6%), and public security (0%–16.7%). Seropositivity rates also varied across occupations, from 15.0% among kitchen staff and 14.4% among nurses, to 5.4% among domestic care workers and 2.8% among journalists. Our findings show that seropositivity rates varied widely across sectors, between facilities within sectors, and across occupations, reflecting a higher exposure in certain sectors and occupations.

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Effective symptom perception may prevent unplanned hospitalizations. However, patients with heart failure (HF) often face challenges that interfere with symptom perception. Little is known about how patients perceive their HF symptoms. Aim: To describe how patients with HF perceive symptoms through the processes of monitoring, awareness, and evaluation. Methods: Using a qualitative descriptive design, we conducted semi-structured in-person interviews with a purposeful sample of adults experiencing an unplanned hospitalization for a HF symptom exacerbation. We elicited how patients monitor, become aware of, and evaluate symptoms prior to hospitalization. Data were analyzed using directed qualitative content analysis. We identified symptom monitoring behaviors, types of symptoms experienced, and success or failure in linking the symptoms to HF. Categories/subcategories were developed by grouping codes based on similarities and differences. Themes were conceptualized at a higher level of abstraction by combining categories. Results: A sample of 40 patients (mean age 62 years, 50% male, median HF duration 6 years, 95% HF stage C/D) was enrolled. Patients demonstrated Body listening , which was the use of active and individualized symptom monitoring tactics that involved observing for bodily changes outside one’s usual range. Trajectory of bodily change involved the patterns or characteristics of bodily changes as they became apparent. Three subthemes— sudden and stunning change , gradual change , and fluctuating change emerged as different Trajectories of bodily changes were identified. The same types of bodily changes could develop in different trajectories. Patients simultaneously experienced all or some of the trajectory types of various symptoms. Patients evaluated symptoms through an Exclusionary process , sequentially attributing symptoms to a cause through a cognitive process of excluding possible causes until the most plausible cause remained. Conclusion: Three major themes emerged from an in-depth description of the complex symptom perception processes of monitoring, awareness, and evaluation. Identifying where patients have difficulties in symptom perception will facilitate the development of tailored interventions.