The impact of COVID-19 control measures on social contacts and transmission in Kenyan informal settlements
This paper is now published Open Access at BMC Medicine here.
Many low- and middle-income countries have implemented control measures against coronavirus disease 2019 (COVID-19). It is not clear if the low numbers of recorded COVID-19 cases and deaths in Africa is due to these. One of the main aims of control measures is to reduce respiratory pathogen transmission through direct contact with others. In this study we collect contact data from residents of informal settlements around Nairobi to assess if control measures have changed contact patterns, and estimate the impact of changes on the reproduction number (R0).
We conducted a social contact survey with 213 residents of five informal settlements around Nairobi in early May 2020, four weeks after the Kenyan government introduced enhanced social distancing measures and a curfew between 7pm and 5am. Respondents were asked to report all direct physical and non-physical contacts made the previous day, alongside a questionnaire asking about the impact of COVID-19 and control measures.
Figure 1. (A) Boxplot showing the number of physical and non-physical contacts reported by socioeconomic quintile, median number labelled. (B) and (C) The estimated value of R0 at the time of the survey, assuming values of R0 ~ Norm(2.6, sd = 0.54) prior to physical distancing reducing contacts.
We estimate that control measures reduced physical and non-physical contacts, reducing the R0 to between 0.6 and 0.7, depending on the pre-COVID-19 comparison matrix used. Masks were worn by at least one person in 92% of contacts. Respondents in the poorest socioeconomic quintile reported 1.5 times more contacts than those in the richest. 86% of respondents reported a total or partial loss of income due to COVID-19, and 74% reported eating less or skipping meals due to having too little money for food.
COVID-19 control measures have had a large impact on direct contacts and therefore transmission, but have also caused considerable economic and food insecurity. Reductions in R0 are consistent with the linear epidemic growth in Kenya and other sub-Saharan African countries that implemented similar, early control measures. However, negative and inequitable impacts on economic and food security may mean control measures are not sustainable in the longer term.