Impact of the Covid-19 epidemic and related social distancing regulations on social contact and SARS-CoV-2 transmission potential in rural South Africa: analysis of repeated cross-sectional surveys

  1. Nicky McCreesh
  2. Vuyiswa Dlamini
  3. Anita Edwards
  4. Stephen Olivier
  5. Njabulo Dayi
  6. Keabetswe Dikgale
  7. Siyabonga Nxumalo
  8. Jaco Dreyer
  9. Kathy Baisley
  10. Mark J. Siedner
  11. Richard G. White
  12. Kobus Herbst
  13. Alison D. Grant
  14. Guy Harling

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Abstract

Background

South 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.

Methods

We 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 (R 0 ). 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’).

Results

Respondents 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 R 0 fell by 42% (95% plausible range 14–59%) between 2019 and June-July 2020.

Conclusions

Extra-household social contact fell substantially following imposition of Covid-19 distancing regulations in rural South Africa. Ongoing contact within intergenerational households highlighted a potential limitation of social distancing measures in protecting older adults.

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  1. Version published to 10.1186/s12879-021-06604-8
  2. ScreenIT

    SciScore for 10.1101/2020.12.01.20241877: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: Ethical approval for UO was granted by the Biomedical Research Ethics Committee (REC) of the University of KwaZulu-Natal (UKZN) (BE662/17) and the London School of Hygiene & Tropical Medicine (14640); ethical approval for CSC was granted by UKZN BREC (BE290/16) and University College London REC (15231/013).
    Consent: Informed consent for participation was recorded in writing for UO and telephonically for CSC.
    RandomizationUO asked about a randomly selected day in the past week; CSC asked about the day prior to interview, limiting data largely to Sunday to Thursday.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Strengths and limitations: There are limitations to this study. As with any observational study of human behaviour, care must be taken in generalising to other populations. While the pre-Covid-19 contact patterns we show here are consistent with those elsewhere in rural Africa,27 as are the changes seen with the arrival of Covid-19,18 it is important to consider whether close contact patterns in rural lower-income settings may have different implications for disease prevention than patterns seen elsewhere. In contrast to social contact surveys that used prospective diaries to capture information, we relied on recent recall – this may have led to some misreporting, but the delay was in all cases less than one week, limiting this concern. Our data were also self-reported rather than, for example, based on proximity detectors or mobility tracking. Self-report can lead to misreporting, although this effect is unlikely to have affected measures of change since we used the same approach for both years. Self-report also has the benefit of providing richer data on the nature of each interaction. Conversely, we kept our questionnaires brief to minimize respondent fatigue, and as a result we do not have certain details about each contact, including whether a facemask was used during each interaction. There are substantial strengths to this work. We were able to compare two studies with respondents drawn from the same well-defined sampling frame asking very similar questions about behav...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  3. Version published to 10.1101/2020.12.01.20241877v1 on medRxiv