The incidence, and spatial trends of cholera in Sabah over 15 years: repeated outbreaks in coastal areas

Maluda, M. C. M., Johnson, E. , Robinson, F., Jikal, M., Fong, S. Y., Saffree, M. J., Fornace, K. M. and Ahmed, K. (2024) The incidence, and spatial trends of cholera in Sabah over 15 years: repeated outbreaks in coastal areas. PLoS Global Public Health, 4(1), e0002861. (doi: 10.1371/journal.pgph.0002861) (PMID:38289918) (PMCID:PMC10826939)

Abstract

Background: Vibrio cholerae remains a notable public health challenge across Malaysia. Although the Malaysian state of Sabah in northern Borneo is considered a cholera-affected area, gaps remain in understanding the epidemiological trends and spatial distribution of outbreaks. This study used case notifications reported over a 15-year period to determine longitudinal and spatial trends in cholera cases to inform disease control measures. Methods: Data were obtained from the Sabah State Health Department for all notified cases of cholera between 2005-2020. Stool samples were collected from the suspected cholera cases and mass rectal swabs were collected after a cholera case was confirmed to identify asymptomatic carriers. Vibrio cholerae was isolated by culture then biotyping and serotyping were done. A cholera outbreak is defined as one or more confirmed cases in a single locality with the evidence of local transmission. All records were geolocated to village level. Satellite-derived data and generalised linearized models were used to assess potential risk factors, including population density, elevation, and distance to the sea. Spatiotemporal clustering of reported cholera cases and zones of increased cholera risk were evaluated using the tau statistic (τ) at 550m, 5km and 10km distances. Results: Over a 15-year period between 2005–2020, 2865 cholera cases were recorded in Sabah, with a mean incidence rate of 5.6 cases per 100,000 (95% CI: 3.4–7.9). From 2015–2020, 705 symptomatic cases and 727 asymptomatic cases were reported. Symptomatic cases primarily occurred in local Malaysian populations (62.6%, 441/705) and in children and adolescents under 15-years old (49.4%, 348/705). Semporna district reported the highest mean incidence rate (20.6/100,000, 95% CI: 0.6–40.7). The highest annual district-level incidence rate was reported from Kudat in 2015, with 51.8 cholera cases per 100,000. On average, cases were reported in areas with low population density (19.45 persons/km2), low elevations (19.45m) and near coastal areas. Spatiotemporal clustering of cholera cases was identified up to 3.5km, with increased village-level cholera risk within 500m and 5 days of initial case presentation to a health facility (Risk Ratio=9.7, 95% CI: 7.5–12.4). Conclusions: Cholera incidence has high spatial and temporal heterogeneity within Sabah, with some districts experiencing repeated outbreaks. Cases occurred mainly along the coastal areas at low elevations and in less populated areas. Cholera cases clustered across space and time, with village-level risk of cholera highest within 5 days and within close proximity to primary case villages, suggesting local transmission Evaluation of transmission patterns in the hotspot districts identified should inform public health interventions for targeted containment strategies in outbreak scenarios.

• Item Type: Articles
• Additional Information: Funding: This work was supported by the Sir Henry Dale fellowship, jointly funded by the Wellcome Trust and Royal Society (grant number 221963/Z/20/Z to KMF), and the Launching Grant for Centre of Excellence from Universiti Malaysia Sabah (grant number AM 18006 to KA).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Johnson, Miss Emilia and Fornace, Dr Kimberly

Creator Roles

Johnson, E.: Data curation, Investigation, Methodology, Software, Validation, Writing – review and editing
Fornace, K.: Formal analysis, Funding acquisition, Methodology, Supervision, Validation, Writing – review and editing

• Authors: Maluda, M. C. M., Johnson, E., Robinson, F., Jikal, M., Fong, S. Y., Saffree, M. J., Fornace, K. M., and Ahmed, K.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: PLoS Global Public Health
• Publisher: Public Library of Science
• ISSN: 2767-3375
• ISSN (Online): 2767-3375
• Copyright Holders: Copyright © 2024 2024 Maluda et al.
• First Published: First published in PLoS Global Public Health 4(1):e0002861
• Publisher Policy: Reproduced under a creative commons licence

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
310866		Socio-ecological dynamics of zoonotic and vector-borne diseases in changing landscapes: implications for surveillance and control	Kimberly Fornace	Wellcome Trust (WELLCOTR)	221963/Z/20/Z	Institute of Biodiversity, Animal Health and Comparative Medicine