Overestimation of Severe Acute Respiratory Syndrome Coronavirus 2 Household Transmission in Settings of High Community Transmission: Insights From an Informal Settlement Community in Salvador, Brazil.
Juan P Aguilar Ticona, Nivison Nery, Matt Hitchings, Emilia M M Andrade Belitardo, Mariam O Fofana, Murilo Dorión, Renato Victoriano, Jaqueline S Cruz, Juliet Oliveira Santana, Laise Eduarda Paixão de Moraes, Cristiane W Cardoso, Guilherme S Ribeiro, Mitermayer G Reis, Ricardo Khouri, Federico Costa, Albert I Ko, Derek A T Cummings
Author Information
Juan P Aguilar Ticona: Instituto de Saúde Coletiva, Universidade Federal da Bahia, Salvador, Bahia, Brazil. ORCID
Nivison Nery: Instituto de Saúde Coletiva, Universidade Federal da Bahia, Salvador, Bahia, Brazil.
Matt Hitchings: Department of Biostatistics, University of Florida, Gainesville, Florida, USA. ORCID
Emilia M M Andrade Belitardo: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Mariam O Fofana: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, USA.
Murilo Dorión: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, USA.
Renato Victoriano: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Jaqueline S Cruz: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Juliet Oliveira Santana: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Laise Eduarda Paixão de Moraes: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Cristiane W Cardoso: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Guilherme S Ribeiro: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Mitermayer G Reis: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Ricardo Khouri: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil. ORCID
Federico Costa: Instituto de Saúde Coletiva, Universidade Federal da Bahia, Salvador, Bahia, Brazil.
Albert I Ko: Fundação Oswaldo Cruz, Instituto Gonçalo Moniz, Ministério da Saúde, Salvador, Bahia, Brazil.
Derek A T Cummings: Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA.
Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread globally. However, the contribution of community versus household transmission to the overall risk of infection remains unclear. Methods: Between November 2021 and March 2022, we conducted an active case-finding study in an urban informal settlement with biweekly visits across 1174 households with 3364 residents. Individuals displaying coronavirus disease 2019 (COVID-19)-related symptoms were identified, interviewed along with household contacts, and defined as index and secondary cases based on reverse-transcription polymerase chain reaction (RT-PCR) and symptom onset. Results: In 61 households, we detected a total of 94 RT-PCR-positive cases. Of 69 sequenced samples, 67 cases (97.1%) were attributed to the Omicron BA.1* variant. Among 35 of their households, the secondary attack rate was 50.0% (95% confidence interval [CI], 37.0%-63.0%). Women (relative risk [RR], 1.6 [95% CI, .9-2.7]), older individuals (median difference, 15 [95% CI, 2-21] years), and those reporting symptoms (RR, 1.73 [95% CI, 1.0-3.0]) had a significantly increased risk for SARS-CoV-2 secondary infection. Genomic analysis revealed substantial acquisition of viruses from the community even among households with other SARS-CoV-2 infections. After excluding community acquisition, we estimated a household secondary attack rate of 24.2% (95% CI, 11.9%-40.9%). Conclusions: These findings underscore the ongoing risk of community acquisition of SARS-CoV-2 among households with current infections. The observed high attack rate necessitates swift booster vaccination, rapid testing availability, and therapeutic options to mitigate the severe outcomes of COVID-19.
