Household transmission of SARS-CoV-2 during the first wave of the COVID-19 pandemic: an analysis of secondary attack rates in Moroccan households.

BACKGROUND

Despite efforts such as lockdowns and social distancing, household transmission remained a key driver of COVID-19 spread in Morocco. Social distancing within households is challenging, and isolating cases over the infectious period is difficult to maintain. Understanding intra-household transmission dynamics during the pandemic's early phase is essential to guide effective public health responses. This retrospective observational study aimed to estimate the secondary attack rate of SARS-CoV-2 among household contacts and identify factors influencing transmission during the first wave of COVID-19 in Morocco.

METHODS

This study enrolled 104 confirmed index cases and 300 household contacts, all tested for SARS-CoV-2 via RT-PCR following the Moroccan Ministry of Health's diagnostic protocol. Participants were categorized based on PCR results. Data were extracted from medical records and supplemented by standardized telephone interviews conducted between March 23 and May 25, 2020. Statistical analyses were performed using IBM SPSS Statistics (version 21).

RESULTS

This study estimated the secondary attack rate of SARS-CoV-2 at 56.3%. A significant association was observed with comorbidities in household contacts (p = 0.015). The rate was lower when the index case was female (aOR: 0.28, 95% CI: 0.16-0.49, p < 0.001) but higher when the index case was symptomatic (aOR: 3.33, 95% CI: 1.95-5.69, p < 0.001). However, the secondary attack rate showed no significant link with the index case's compliance with infection control measures, whether inside or outside the household.

CONCLUSION

This study revealed a high secondary attack rate of SARS-CoV-2 in households during the first wave of the COVID-19 pandemic. These findings offer critical insights for designing targeted preventive measures to curb household transmission in future COVID-19 waves or similar pandemics.