Impact of social distancing regulations and epidemic risk perception on social contact and SARS-CoV-2 transmission potential in rural South Africa: analysis of repeated cross-sectional surveys

Abstract

BackgroundSouth Africa implemented rapid and strict physical distancing regulations to minimize SARS-CoV-2 epidemic spread. Evidence on the impact of such measures on interpersonal contact in rural and lower-income settings is limited.MethodsWe compared population-representative social contact surveys conducted in the same rural KwaZulu-Natal location once in 2019 and twice in mid-2020. Respondents reported characteristics of physical and conversational (‘close interaction’) contacts over 24 hours. We built age-mixing matrices and estimated the proportional change in the SARS-CoV-2 reproduction number (R0). Respondents also reported counts of others present at locations visited and transport used, from which we evaluated change in potential exposure to airborne infection due to shared indoor space (‘shared air’).ResultsRespondents in March-December 2019 (n=1704) reported a mean of 7.4 close interaction contacts and 196 shared air person-hours beyond their homes. Respondents in June-July 2020 (n=216), as the epidemic peaked locally, reported 4.1 close interaction contacts and 21 shared air person-hours outside their home, with significant declines in others’ homes and public spaces. Adults aged over 50 had fewer close contacts with others over 50, but little change in contact with 15-29 year olds, reflecting ongoing contact within multigenerational households. We estimate potential R0 fell by 42% (95% plausible range 14-59%) between 2019 and June-July 2020.DiscussionExtra-household social contact fell substantially following imposition of Covid-19 distancing regulations in rural South Africa. Ongoing contact within intergenerational households highlighted the limitation of social distancing measures in protecting older adults.FundingWellcome Trust, UKRI, DFID, European Union

Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: systematic review and meta-analysis

“…This review attempted to assess the overall effectiveness of the public health intervention packages by reporting the percentage difference in outcome before and after implementation of measures or between regions or countries studied. Eleven of the 37 included studies noted a difference of between 26% and 50% in transmission of SARS-CoV-2 and incidence of covid-19,7172737475767778798081 nine noted a difference of between 51% and 75% in SARS-CoV-2 transmission, covid-19 incidence, and covid-19 mortality,828384858687888990 and 14 noted a difference of more than 75% in transmission of SARS-CoV-2, covid-19 incidence and covid-19 mortality 808190919293949596979899100101. For the remaining studies, the overall effectiveness was not assessed owing to a lack of comparators (see supplementary material 3, table 3).…”

Rapid review of social contact patterns during the COVID-19 pandemic

“…The majority (8/12) of studies were based in high-income countries: European countries (n=6), the United States (n=1) or both (n=1). Eight studies surveyed participants with the intention of describing contact patterns representative of an entire country 33–40 and four studies aimed to describe sub-national areas such as cities (Shanghai and Wuhan in one study, Shenzhen and Changsha in a second) 41,42 , an informal settlement in Nairobi, Kenya 43 and a district in KwaZulu-Natal, South Africa 44 . Six studies included adults aged 18 years and above only 33,35–37,39,43 , four studies included participants of all ages 34,40–42 and two studies included teenagers and above 38,44 .…”

“…Eleven 33–43 studies collected data during the initial mitigation period between February and May 2020 with the most stringent physical distancing measures (Figure 2) with seven 33–35,37–40 collecting data during nationally-declared lockdown and four 36,41–43 during regional lockdown. Five 34–36,38,42 studies also collected additional data when interventions were relaxed (April and May for China and between May and September for other settings) and one 44 study collected data exclusively during the period of relaxation 44 . Policies in place during data collection period were similar but varied (SI.6, SI.16) as did the epidemic situation (SI.5).…”

“…Policies in place during data collection period were similar but varied (SI.6, SI.16) as did the epidemic situation (SI.5). The majority of studies were one-time cross-sectional surveys 34,37,39–43 , one was longitudinal (a cohort of participants repeatedly responded to surveys over time) 35 and four were repeated cross-sectional surveys (surveys were repeated over time with different participants) 33,36,38,44 . The majority (7/12) used online surveys to recruit participants and collect contact data, while the remaining studies were conducted using phone-based surveys.…”

Estimating the contribution of transmission in primary healthcare clinics to community-wide TB disease incidence, and the impact of infection prevention and control interventions, in KwaZulu-Natal, South Africa

“…The social contact data used in our model were collected in 2019, before the start of the COVID-19 pandemic. Comparable social contact data were collected from the same study community in June-August 2020, during the pandemic, and suggested that reductions in contact time in clinics may have been smaller than reductions in other congregate locations 7 , possibly increasing the importance of transmission in clinics to overall disease burden during this period. The IPC interventions we simulated were also designed and parameterised before the start of the pandemic, and changing views on IPC may have changed the relative impact of the different interventions over longer time periods.…”