Incidence, household transmission, and neutralizing antibody seroprevalence of Coronavirus Disease 2019 in Egypt: Results of a community-based cohort

Abstract

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.

Factors Associated With Household Transmission of SARS-CoV-2

“…Compared with the SAR for 28 studies 12,14,17,27,94 from January to February 2020 (13.4%; 95% CI, 10.7%-16.7%), the SAR was significantly higher for 30 studies 6,7,15,16,19,22,25,26,28,30,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86]93 from March to April 2020 (19.4%; 95% CI, 15.2%-24.5%; P = .03) and 15 studies 5,8,10,18,20,21,23,24,29,31,32,35,37,38,40 from July 2020 to March 2021 (31.1%; 95% CI, 22.6%-41.1%; P < .001) but not significantly different from the SAR for 14 studies…”

“…To elucidate factors associated with differences in SAR, we explored attributes of studies from the periods with the lowest and highest household SARs. Among 28 studies 12,14,17,27,94 from January to February 2020 and 15 studies 5,8,10,18,20,21,23,24,29,31,32,35,37,38,40 from July 2020 to March 2021, 6 studies 12,46,54,57,59,62 (21.4%) and 4 studies 8,10,20,23 (25.0%), respectively, reported testing contacts at least twice, 1 study 46 (3.6%) and 3 studies 5,8,23 (18.8%) reported following contacts for longer than 14 days, 1 study 45 (3.6%) and 6 studies 8,23,24,29,37,40 (33.3%) were published as preprints, 21 studies 12,14,27,46,[48][49][50]…”

“…The estimated overall household SAR for all 87 studies was 18.9% (95% CI, 16.2%-22.0%), with significant heterogeneity ( I 2 = 99.4%; P < .001) ( Figure 2 ). Excluding studies with only asymptomatic 85 or pediatric 36 , 66 index cases, studies that tested only 7 , 9 , 15 , 17 , 19 , 24 , 26 , 29 , 30 , 31 , 35 , 37 , 45 , 47 , 61 , 65 , 68 , 69 , 71 , 77 , 79 , 81 , 82 , 86 , 87 , 90 , 92 , 94 or asymptomatic 78 contacts, studies with long follow-up periods (≥21 days), 5 , 8 , 9 , 23 , 46 , 92 and studies published as preprints, 8 , 23 , 24 , 29 , 45 , 79 , 88 , 89 , 90 , 92 the overall SAR among the 47 remaining studies 4 , 6 , 10 , 11 , 12 , 13 , 14 , …”

“…Characteristics of Studies Included in Analysis of Household Secondary Attack Rates for SARS-CoV-2 (continued) ,23,24,29,37,40,45,79,[88][89][90]92 21.0(13.8-30.6) No 75[4][5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22][25][26][27][28][30][31][32][33][34][35][36][37][38][39][74][75][76][77][78][80][81][82][83][84]…”

Date of introduction and epidemiologic patterns of SARS-CoV-2 in Mogadishu, Somalia: estimates from transmission modelling of 2020 excess mortality data

“…While some of this difference can be potentially explained by a lower infection fatality ratio (IFR) for the entire population due to a lower median age (2)(3)(4), evidence suggests that at least critically ill COVID-19 African patients experience higher, not lower mortality than elsewhere (5), as plausibly expected due to weaker health infrastructure (6). News reports (7), studies using seroprevalence (8,9), PCR testing in morgues (10), as well as indirect data sources such as obituaries on social media (11) point to substantial under-ascertainment of cases and deaths in low-income countries, potentially ten-fold (suggested by excess mortality data from Egypt (12)) or even nearly hundred-fold (13) in crisis-ridden regions. While in high income countries (12) confirmed COVID-19 deaths are approximately in line with excess death statistics, in many African countries there are no reliable mortality statistics, precluding the use of excess deaths to infer the true scale of the pandemic.…”