Population-Based Study of anti-SARS-CoV-2, Social Distancing and Government Responses in Joinville, Brazil

Background: The city of Joinville had been mildly affected by the COVID-19 pandemic until June 2020. This study aimed to longitudinally assess the prevalence of exposure to the virus and social distancing practices in the local population. Methods: A randomized selection of households stratified by region was created. From June 15 to August 7, 2020, a dweller was randomized in each household, answered a questionnaire, and performed a test for the detection of SARS-CoV-2 antibodies. The prevalence of positive tests was calculated for each week and adjusted for the test's sensitivity and specificity. Results: The adjusted proportion of positive results increased from 1.4% in the first week (margin of error [ME] 0% to 2.87%) to 13.38% in the eighth week (ME 10.22% to 16.54%). Among the 213 participants that tested positive, 55 (25.82%) were asymptomatic. Only 37 (17.37%) sought medical consultation for any symptom. Among the 77 (36.15%) that were leaving home to work or study, only 18 (23.38%) stopped due to any symptom. The proportion that referred going to bars, restaurants, or making non-essential shopping decreased from 20.56% in the first week to 8.61% during the peak of diagnoses. Conclusion: The low proportion of participants that sought medical consultation or stopped leaving home indicates strategies directed to isolate only those symptomatic reach a low proportion of infected patients.