Abstract
ABSTRACTOBJECTIVE To estimate the evolution of the prevalence of SARS-CoV-2 virus infection among residents aged 18 years or over in the municipality of São Paulo.METHODS This is a population-based household survey conducted every 15 days, between June and September 2020, and January and February 2021. In total, the study comprised 11 phases. The presence of antibodies against SARS-CoV-2 was identified in venous blood using a lateral flow test, Wondfo Biotech. In the last phase, the researchers combined it with an immunoenzymatic test, Euroimmun. The participants also answered a semi-structured questionnaire on sociodemographic and economic factors, and on social distancing measures. Prevalence estimates and the 95% confidence interval were estimated according to regions, Human Development Index, sex, age group, ethnicity, education, income, and variables associated with risk or prevention of infection. To compare the frequencies among the categories of each variable, the chi-square test with Rao-Scott correction was used, considering a significance level of 5%.RESULTS In total, 23,397 individuals were interviewed and had their samples collected. The estimated prevalence of antibodies against SARS-CoV-2 ranged from 9.7% (95%CI: 7.9–11.8%) to 25.0% (95%CI: 21.7–28.7). The prevalence of individuals with antibodies against the virus was higher among black and brown people, people with lower schooling and income, and among residents of regions with lower Human Development Index. The lowest prevalences were associated with recommended measures of disease protection. The proportion of asymptomatic infection was 45.1%.CONCLUSION The estimated prevalence of the infection was lower than the cumulative incidence variation, except for the last phase of the study. The differences in prevalence estimates observed among subpopulations showed social inequality as a risk of infection. The lower prevalence observed among those who could follow prevention measures reinforce the need to maintain social distancing measures as a way to prevent SARS-CoV-2 infection.
Highlights
In December 2019, the World Health Organization (WHO) received a notification of pneumonia outbreak in Wuhan, Hubei Province, People’s Republic of China
The estimated prevalence of antibodies against severe acute respiratory syndrome (SARS)-CoV-2 ranged from 9.7% (95%confidence intervals (CI): 7.9–11.8%) to 25.0% (95%CI: 21.7–28.7)
The estimated prevalence of the infection was lower than the cumulative incidence variation, except for the last phase of the study
Summary
In December 2019, the World Health Organization (WHO) received a notification of pneumonia outbreak in Wuhan, Hubei Province, People’s Republic of China. The etiological agent was quickly identified: a new coronavirus called SARS-CoV-2. On January 30, 2020, WHO declared the disease outbreak caused by the virus (COVID-19) a Public Health Emergency of International Concern (PHEIC), the highest WHO alert level according to International Health Regulations (IHR). On March 11, 2020, WHO declared the outbreak of COVID-19 a global pandemic[1]. In Brazil, the Ministry of Health (MoH) declared the outbreak a Public Health Emergency of National Concern (PHENC) on February 3, 20202. The first case was diagnosed on February 26, 2020, and on March 20, 2020, MoH announced the community transmission of COVID-19 in the national territory[3]
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