Background Households are among the highest risk for the transmission of SARS‐CoV‐2. In sub‐Saharan Africa, very few studies have described household transmission during the COVID‐19 pandemic. Our work aimed to describe the epidemiologic parameters and analyze the secondary attack rate (SAR) in Antananarivo, Madagascar, following the introduction of SARS‐CoV‐2 in the country in March 2020. Methods A prospective case‐ascertained study of all identified close contacts of laboratory‐confirmed COVID‐19 infections was conducted in Antananarivo from March to June 2020. Cases and household contacts were followed for 21 days. We estimated epidemic parameters of disease transmission by fitting parametric distributions based on infector‐infected paired data. We assessed factors influencing transmission risk by analyzing the SAR. Findings Overall, we included 96 index cases and 179 household contacts. Adjusted with the best‐fit normal distribution, the incubation period was 4.1 days (95% CI 0.7–7.5]). The serial interval was 6.0 days (95% CI [2.4–9.6]) after adjusting with the best‐fit Weibull distribution. On average, each index case infected 1.6 family members (95%CI [0.9–2.3]). The mean SAR among close contacts was 38.8% (95% CI [19.5–58.2]) with the best‐fit gamma distribution. Contacts older than 35 years old were more likely to be infected, and the highest SAR was found among them. Conclusion The results of our study provide key insights into the epidemiology of the first wave of SARS‐CoV‐2 in Madagascar. High rates of household transmission were found in Antananarivo, emphasizing the need for preventive measures to reduce community transmission.

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Background Health care workers (HCWs) represent a vulnerable population during epidemic periods. Our cohort study aimed to estimate the risk of infection and associated factors among HCWs during the first wave of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in Madagascar. Methods A prospective cohort study was carried out in three hospitals that oversaw the first cases of COVID‐19. Monthly ELISA‐based serological tests were conducted, and nasopharyngeal swabs were collected in the case of symptoms linked to COVID‐19 for RT–PCR analysis. Survival analyses were used to determine factors associated with SARS‐CoV‐2 infection. Results The study lasted 7 months from May 2020. We included 122 HCWs, 61.5% of whom were women. The median age was 31.9 years (IQR: 26.4–42.3). In total, 42 (34.4%) had SARS‐CoV‐2 infections, of which 20 were asymptomatic (47.6%). The incidence of SARS‐CoV‐2 infection was 9.3% (95% CI [6.5–13.2]) person‐months. Sixty‐five HCWs presented symptoms, of which 19 were positive by RT–PCR. When adjusted for exposure to deceased cases, infection was more frequent in HCWs younger than 30 years of age (RR = 4.9, 95% CI [1.4–17.2]). Conclusion Our results indicate a high incidence of infection with SARS‐CoV‐2 among HCWs, with a high proportion of asymptomatic cases. Young HCWs are more likely to be at risk than others. Greater awareness among young people is necessary to reduce the threat of infection among HCWs.

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