A micro-epidemiological analysis of febrile malaria in Coastal Kenya showing hotspots within hotspots

  1. Philip Bejon  Is a corresponding author
  2. Thomas N Williams
  3. Christopher Nyundo
  4. Simon I Hay
  5. David Benz
  6. Peter W Gething
  7. Mark Otiende
  8. Judy Peshu
  9. Mahfudh Bashraheil
  10. Bryan Greenhouse
  11. Teun Bousema
  12. Evasius Bauni
  13. Kevin Marsh
  14. David L Smith
  15. Steffen Borrmann
  1. Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kenya
  2. Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, United Kingdom
  3. University of Oxford, United Kingdom
  4. University of California, San Francisco, United States
  5. London School of Hygiene and Tropical Medicine, United Kingdom
  6. John Hopkins Malaria Research Institute, United States

Abstract

Malaria transmission is spatially heterogeneous. This reduces the efficacy of control strategies, but focusing control strategies on clusters or 'hotspots' of transmission may be highly effective. Among 1,500 homesteads in coastal Kenya we calculated a) the fraction of febrile children with positive malaria smears per homestead, and b) the mean age of children with malaria per homestead. These two measures were inversely correlated, indicating that children in homesteads at higher transmission acquire immunity more rapidly. This inverse correlation increased gradually with increasing spatial scale of analysis, and hotspots of febrile malaria were identified at every scale. We found hotspots within hotspots, down to the level of an individual homestead. Febrile malaria hotspots were temporally unstable, but 4km radius hotspots could be targeted for one month following one month periods of surveillance.

Article and author information

Author details

  1. Philip Bejon

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    For correspondence
    pbejon@kemri-wellcome.org
    Competing interests
    The authors declare that no competing interests exist.
  2. Thomas N Williams

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  3. Christopher Nyundo

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  4. Simon I Hay

    University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  5. David Benz

    University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  6. Peter W Gething

    University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  7. Mark Otiende

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  8. Judy Peshu

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  9. Mahfudh Bashraheil

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  10. Bryan Greenhouse

    University of California, San Francisco, San Francisco, United States
    Competing interests
    The authors declare that no competing interests exist.
  11. Teun Bousema

    London School of Hygiene and Tropical Medicine, London, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  12. Evasius Bauni

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  13. Kevin Marsh

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.
  14. David L Smith

    John Hopkins Malaria Research Institute, Baltimore, United States
    Competing interests
    The authors declare that no competing interests exist.
  15. Steffen Borrmann

    Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Kilifi, Kenya
    Competing interests
    The authors declare that no competing interests exist.

Ethics

Human subjects: Informed consent for participation was obtained, and specific ethical approval was obtained from the KEMRI Ethical Review Committee (SSC Protocol No. 2413: Spatial Epidemiology of Malaria Cases in the Kilifi District Demographic Surveillance Area). The KEMRI ethical review committee required that participants consent for participation in research and for their data to be stored, but does not require a further explicit statement consenting to publication. Our institutional guidelines would require this only in the event that individuals were identifiable in the publication.

Reviewing Editor

  1. Mercedes Pascual, University of Michigan, United States

Publication history

  1. Received: December 19, 2013
  2. Accepted: April 1, 2014
  3. Accepted Manuscript published: April 24, 2014 (version 1)
  4. Version of Record published: April 29, 2014 (version 2)

Copyright

© 2014, Bejon et al.

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

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  1. Philip Bejon
  2. Thomas N Williams
  3. Christopher Nyundo
  4. Simon I Hay
  5. David Benz
  6. Peter W Gething
  7. Mark Otiende
  8. Judy Peshu
  9. Mahfudh Bashraheil
  10. Bryan Greenhouse
  11. Teun Bousema
  12. Evasius Bauni
  13. Kevin Marsh
  14. David L Smith
  15. Steffen Borrmann
(2014)
A micro-epidemiological analysis of febrile malaria in Coastal Kenya showing hotspots within hotspots
eLife 3:e02130.
https://doi.org/10.7554/eLife.02130

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    Background: Worldwide, most colorectal cancer screening programmes were paused at the start of the COVID-19 pandemic, whilst the Danish faecal immunochemical test (FIT)-based programme continued without pausing. We examined colorectal cancer screening participation and compliance with subsequent colonoscopy in Denmark throughout the pandemic.

    Methods: We used data from the Danish Colorectal Cancer Screening Database among individuals aged 50-74 years old invited to participate in colorectal cancer screening from 2018-2021 combined with population-wide registries. Using a generalised linear model, we estimated prevalence ratios (PR) and 95% confidence intervals (CI) of colorectal cancer screening participation within 90 days since invitation and compliance with colonoscopy within 60 days since a positive FIT test during the pandemic in comparison with the previous years adjusting for age, month and year of invitation.

    Results: Altogether, 3,133,947 invitations were sent out to 1,928,725 individuals and there were 94,373 positive FIT tests (in 92,848 individuals) during the study period. Before the pandemic, 60.7% participated in screening within 90 days. A minor reduction in participation was observed at the start of the pandemic (PR=0.95; 95% CI: 0.94-0.96 in pre-lockdown and PR=0.85; 95% CI: 0.85-0.86 in 1st lockdown) corresponding to a participation rate of 54.9% during pre-lockdown and 53.0% during 1st lockdown. This was followed by a 5-10% increased participation in screening corresponding to a participation rate of up to 64.9%. The largest increase in participation was observed among 55-59 year olds and among immigrants. The compliance with colonoscopy within 60 days was 89.9% before the pandemic. A slight reduction was observed during 1st lockdown (PR=0.96; 95% CI: 0.93-0.98), where after it resumed to normal levels.

    Conclusions: Participation in the Danish FIT-based colorectal cancer screening programme and subsequent compliance to colonoscopy after a positive FIT result was only slightly affected by the COVID-19 pandemic.

    Funding: The study was funded by the Danish Cancer Society Scientific Committee (grant number R321-A17417) and the Danish regions.