Sars-cov-2 transmission among first cases and their contacts in kisumu county, Kenya

ABSTRACT

Background: To inform epidemic control strategies in Kisumu County, Kenya, we examined exposures and presumed routes of SARS-CoV-2 transmission among the first identified cases and their contacts in the county. Methods: Between June 10, 2020 and September 21, 2020, we enrolled the first identified SARS-CoV-2 PCR positive cases in Kisumu County. Across the enrollment period, strict shelter-in-place and curfew mandates were gradually loosened. Enrolled cases were asked to identify all persons who were within 2 meters of them, between 48 hours prior to symptoms through the time of the enrollment interview;multiple attempts were made to reach and enroll each named contact. All cases and contacts answered detailed questionnaires about recent potential exposures at enrollment and 2 weeks later. Contacts with SARS-CoV-2 PCR positive tests at either visit were enrolled as “secondary” cases and presumed to have acquired infection from the index case who named them as a contact. Results: We enrolled 152 cases (125 index and 27 secondary) cases and 248 contacts, including 27 contacts (11%) who acquired infection and also enrolled as secondary cases. Among all cases, 59% were male and the median age was 35 years (interquartile range [IQR] 28, 44). Among contacts, 51% were male and the median age was 24 years (IQR 11.2, 35.2). While the earliest identified SARSCoV- 2 infections in Kisumu County were among truck drivers, as others started returning to work, community transmission escalated. Within 3 months from the first identified case in the county, office workers represented the largest occupation category among cases (37%) (Figure). A total of 12 index cases (10%) transmitted to the 27 contacts who acquired infection. Among these 27 secondary cases, 85% were household members of index cases and 48% were <15 years old. Conclusion: Within 3 months from the first identified case of SARS-CoV-2 infection in Kisumu County, office workers had the highest risk of infection, suggesting a need for more rigorously applied physical distancing and masking policies as employees of non-essential services return to work. While transmission from cases to contacts was relatively low, the vast majority occurred within households and children were disproportionately represented among secondary cases. Enhanced support for within-household distancing during the isolation of cases may be needed. Given the concurrent increase in office-worker infections, undetected community transmission outside our enrolled cohort likely occurred.