{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T05:15:36Z","timestamp":1790745336656,"version":"4.1.0"},"reference-count":29,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T00:00:00Z","timestamp":1635984000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Public Health"],"abstract":"<jats:p><jats:bold>Background:<\/jats:bold> Knowledge on the settings and activities associated with a higher risk of SARS-CoV-2 transmission is essential to inform decision-making. We thus designed a case-control study to identify relevant settings for community transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Portugal.<\/jats:p><jats:p><jats:bold>Methods:<\/jats:bold> We evaluated 1,088 cases, identified through the national surveillance system, and 787 community controls, recruited using random digit dialing. Sociodemographic characteristics, individual protective measures, and activities or visited settings were obtained through telephone interview. We report sex-, age-, education-, and citizenship-adjusted odds ratios (aOR) with 95% confidence intervals (95% CI).<\/jats:p><jats:p><jats:bold>Results:<\/jats:bold> Household overcrowding (aOR = 1.47; 95% CI 1.14\u20131.91) and work in senior care (4.99; 1.30\u201333.08) increased while working remotely decreased the risk of infection (0.30; 0.22\u20130.42). Going to restaurants\/other dining spaces (0.73; 0.59\u20130.91), grocery stores (0.44; 0.34\u20130.57) or hair salons (0.51; 0.39\u20130.66), or the use of public transportation did not present a higher risk of infection (0.98; 0.75\u20131.29), under existing mitigation strategies. Lower education ( \u2264 4 years vs. tertiary education: 1.79; 1.33\u20132.42) and no Portuguese citizenship (5.47; 3.43\u20139.22) were important risk factors.<\/jats:p><jats:p><jats:bold>Conclusions:<\/jats:bold> The utilization of public transportation, restaurants, and commercial spaces was not associated with increased risk of infection, under capacity restrictions, physical distancing, use of masks, and hygiene measures. Overcrowding, foreign citizenship, low education and working on-site were positively associated with SARS-CoV-2 infection.<\/jats:p>","DOI":"10.3389\/fpubh.2021.772782","type":"journal-article","created":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T05:44:40Z","timestamp":1636004680000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":20,"title":["A Case-Control Study of Contextual Factors for SARS-CoV-2 Transmission"],"prefix":"10.3389","volume":"9","author":[{"given":"Andreia","family":"Leite","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Teresa","family":"Le\u00e3o","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Patr\u00edcia","family":"Soares","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Milton","family":"Severo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marta","family":"Moniz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Raquel","family":"Lucas","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pedro","family":"Aguiar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paula","family":"Meireles","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nuno","family":"Lunet","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carla","family":"Nunes","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Henrique","family":"Barros","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2021,11,4]]},"reference":[{"key":"B1","unstructured":"Data on Country Response Measures to COVID-19 [Internet].2021"},{"key":"B2","volume-title":"Considerations relating to social distancing measures in response to the COVID-19 epidemic","year":"2020"},{"key":"B3","doi-asserted-by":"publisher","first-page":"44","DOI":"10.5089\/9781513550251.001","article-title":"The economic effects of COVID-19 containment measures","volume":"20","author":"Deb","year":"2020","journal-title":"IMF Work Pap."},{"key":"B4","doi-asserted-by":"publisher","first-page":"33","DOI":"10.1016\/S0092-8240(05)80040-0","article-title":"Contributions to the mathematical theory of epidemics","volume":"53","author":"Kermarck","year":"1991","journal-title":"Bull Math Biol."},{"key":"B5","doi-asserted-by":"publisher","first-page":"493","DOI":"10.1126\/science.abb4218","article-title":"The effect of human mobility and control measures on the COVID-19 epidemic in China","volume":"497","author":"Kraemer","year":"2020","journal-title":"Science."},{"key":"B6","doi-asserted-by":"publisher","first-page":"713","DOI":"10.1016\/j.physa.2018.07.025","article-title":"Effect of population density on epidemics","volume":"510","author":"Li","year":"2018","journal-title":"Phys A Stat Mech Appl."},{"key":"B7","doi-asserted-by":"publisher","first-page":"964","DOI":"10.1136\/jech-2020-214401","article-title":"The COVID-19 pandemic and health inequalities","volume":"74","author":"Bambra","year":"2020","journal-title":"J Epidemiol Community Health."},{"key":"B8","first-page":"979","article-title":"Household transmission of COVID-19-a systematic review and meta-analysis","volume-title":"J Infect.","author":"Lei","year":"2020"},{"key":"B9","doi-asserted-by":"publisher","first-page":"333","DOI":"10.1016\/S1473-3099(20)30833-1","article-title":"SARS-CoV-2 seroprevalence and transmission risk factors among high-risk close contacts: a retrospective cohort study","volume":"21","author":"Ng","year":"2020","journal-title":"Lancet Infect Dis"},{"key":"B10","doi-asserted-by":"publisher","first-page":"847","DOI":"10.15585\/mmwr.mm6926e4","article-title":"Exposures before issuance of stay-at-home orders among persons with laboratory-confirmed COVID-19 - Colorado, March (2020)","volume":"69","author":"Marshall","year":"2020","journal-title":"MMWR Morb Mortal Wkly Rep."},{"key":"B11","doi-asserted-by":"publisher","first-page":"1258","DOI":"10.15585\/mmwr.mm6936a5","article-title":"Community and close contact exposures associated with COVID-19 among symptomatic adults \u226518 years in 11 outpatient health care facilities \u2014 United States, July (2020)","volume":"69","author":"Fisher","year":"2020","journal-title":"MMWR Morb Mortal Wkly Rep."},{"key":"B12","volume-title":"Etude des facteurs sociod\u00e9mographiques, comportements et pratiques associ\u00e9s \u00e0 l'infection par le SARS-CoV-2 (ComCor)","author":"Galmiche","year":"2020"},{"key":"B13","doi-asserted-by":"publisher","first-page":"100148","DOI":"10.1016\/j.lanepe.2021.100148","article-title":"Exposures associated with SARS-CoV-2 infection in France: a nationwide online case-control study","volume":"7","author":"Galmiche","year":"2021","journal-title":"Lancet Reg Heal Eur"},{"key":"B14","first-page":"167","volume-title":"Methodological Guidelines and Description of EU-SILC Target Variables","year":"2018"},{"key":"B15","volume-title":"Resolu\u00e7\u00e3o do Conselho de Ministros 88\/2020. Di\u00e1rio da Rep\u00fablica - I S\u00e9rie-B","year":"2020"},{"key":"B16","doi-asserted-by":"publisher","first-page":"730","DOI":"10.1093\/aje\/kwv114","article-title":"Asymptotically unbiased estimation of exposure odds ratios in complete records logistic regression","volume":"182","author":"Bartlett","year":"2015","journal-title":"Am J Epidemiol."},{"key":"B17","doi-asserted-by":"publisher","first-page":"353","DOI":"10.1076\/edre.7.4.353.8937","article-title":"A review of methods for missing data","volume":"7","author":"Pigott","year":"2001","journal-title":"Educ Res Eval."},{"key":"B18","volume-title":"R: A Language and Environment for Statistical Computing","year":"2019"},{"key":"B19","doi-asserted-by":"publisher","first-page":"874","DOI":"10.1016\/S0140-6736(20)32000-6","article-title":"Offline: COVID-19 is not a pandemic","volume":"396","author":"Horton","year":"2020","journal-title":"Lancet"},{"key":"B20","unstructured":"Migrant Integration Statistics\u2013Housing [Internet]. Eurostat Statistics Explained.2021"},{"key":"B21","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/j.jmh.2021.100041","article-title":"Clinical outcomes and risk factors for COVID-19 among migrant populations in high-income countries: a systematic review","volume":"3","author":"Hayward","year":"2021","journal-title":"J Migr Heal"},{"key":"B22","doi-asserted-by":"publisher","first-page":"611565","DOI":"10.3389\/fpubh.2021.611565","article-title":"Urban rail transportation and SARS-Cov-2 infections: an ecological study in the Lisbon metropolitan area","volume":"9","author":"Severo","year":"2021","journal-title":"Front Public Heal."},{"key":"B23","unstructured":"R115\u2013Workers' Housing Recommendation [Internet].2021"},{"key":"B24","volume-title":"Reducing COVID 19 Transmission Strengthening Vaccine Uptake Among Migrant Populations in the EU\/EEA","year":"2021"},{"key":"B25","doi-asserted-by":"publisher","first-page":"1145","DOI":"10.1038\/s41562-021-01181-x","article-title":"A worldwide assessment of changes in adherence to COVID-19 protective behaviours and hypothesized pandemic fatigue","volume":"5","author":"Petherick","year":"2021","journal-title":"Nat Hum Behav"},{"key":"B26","first-page":"1","article-title":"Lockdown fatigue: the diminishing effects of quarantines on the spread of COVID-19","volume-title":"Covid Econ.","author":"Goldstein","year":"2021"},{"key":"B27","volume-title":"Perfil Regional Saude LVT","year":"2017"},{"key":"B28","article-title":"Plano Local de Sa\u00fade 2014-2016","volume-title":"Public Health Unit.","author":"Santos","year":"2014"},{"key":"B29","doi-asserted-by":"publisher","first-page":"205","DOI":"10.1093\/ije\/19.1.205","article-title":"Case-control designs in the study of common diseases: updates on the demise of the rare disease assumption and the choice of sampling scheme for controls","volume":"19","author":"Rodrigues","year":"1990","journal-title":"Int J Epidemiol"}],"container-title":["Frontiers in Public Health"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fpubh.2021.772782\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T05:44:48Z","timestamp":1636004688000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fpubh.2021.772782\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,11,4]]},"references-count":29,"alternative-id":["10.3389\/fpubh.2021.772782"],"URL":"https:\/\/doi.org\/10.3389\/fpubh.2021.772782","relation":{},"ISSN":["2296-2565"],"issn-type":[{"value":"2296-2565","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,11,4]]},"article-number":"772782"}}