Incidence, Household Transmission, And Neutralizing Antibody Seroprevalence Of Coronavirus Disease 2019 In Egypt: Results Of A Community-Based Cohort

Author summarySARS-CoV-2 virus is transmitted via close contact with infected persons, airborne droplets, and contaminated surfaces. People in closed settings with COVID-19 patients, such as healthcare workers and household contacts, were more likely to become infected. Egypt, like all other countries, is currently facing the COVID-19 pandemic. However, data on incidence and seroprevalence in this country is lacking. We followed 290 households participating in an ongoing cohort study of influenza and coronavirus incidence and prevalence. The incidence of COVID-19 was 6.9% and the household secondary attack rate was 89.8%. Transmission within households occurred within two-days of confirming the index case. Infections were asymptomatic or mild with symptoms resolving within 10 days. The majority developed a neutralizing antibody titer by day 14 post onset. The overall seroprevalence among cohort participants was 34.8%. The majority of subjects with three months apart paired-samples continued to be seropositive. Within-household transmission is high. Asymptomatic or mild illness is common. Most infections seroconvert and have a durable neutralizing antibody titer. Increasing awareness among the general public about proper ways of dealing with infections within the household may contribute to decreasing the spread in Egypt and areas with similar cultural background and population structure.SARS-CoV-2 virus is transmitted in closed settings to people in contact with COVID-19 patients such as healthcare workers and household contacts. However, household person-to-person transmission studies are limited. Households participating in an ongoing cohort study of influenza incidence and prevalence in rural Egypt were followed. Baseline enrollment was done from August 2015 to March 2017. The study protocol was amended in April 2020 to allow COVID-19 incidence and seroprevalence studies. A total of 290 households including 1598 participants were enrolled and followed from April to October 2020 in four study sites. When a participant showed respiratory illness symptoms, a serum sample and a nasal and an oropharyngeal swab were obtained. Swabs were tested by RT-PCR for SARS-CoV-2 infection. If positive, the subject was followed and swabs collected on days three, six, nine, and 14 after the first swab day and a serum sample obtained on day 14. All subjects residing with the index case were swabbed following the same sampling schedule. Sera were collected from cohort participants in October 2020 to assess seroprevalence. Swabs were tested by RT-PCR. Sera were tested by Microneutralization Assay to measure the neutralizing antibody titer. Incidence of COVID-19, household secondary attack rate, and seroprevalence in the cohort were determined. The incidence of COVID-19 was 6.9% and the household secondary attack rate was 89.8%. Transmission within households occurred within two-days of confirming the index case. Infections were asymptomatic or mild with symptoms resolving within 10 days. The majority developed a neutralizing antibody titer by day 14 post onset. The overall seroprevalence among cohort participants was 34.8%. These results suggest that within-household transmission is high in Egypt. Asymptomatic or mild illness is common. Most infections seroconvert and have a durable neutralizing antibody titer.