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Environmental temperature and case fatality of patients with Ebola virus disease in Sierra Leone and Liberia, 2014–2015: a retrospective cohort study
Author(s) -
Peters Jillian L.,
Cho Daniel K.,
Aluisio Adam R.,
Kennedy Stephen B.,
Massaquoi Moses B. F.,
Sahr Foday,
Perera Shiromi M.,
Levine Adam C.
Publication year - 2019
Publication title -
tropical medicine and international health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.056
H-Index - 114
eISSN - 1365-3156
pISSN - 1360-2276
DOI - 10.1111/tmi.13166
Subject(s) - sierra leone , ebola virus , medicine , case fatality rate , confounding , logistic regression , environmental health , cohort , demography , emergency medicine , disease , population , sociology , development economics , economics
Objective Fluid loss during Ebola virus disease ( EVD ) infections from gastrointestinal dysfunction leads to volume depletion. It is possible that high environmental temperatures may exacerbate volume depletion or interfere with the provision of medical care by providers in full personal protective equipment. We investigated the effect of environmental temperature on case fatality. Methods The International Medical Corps ( IMC ) operated five Ebola Treatment Units ( ETU s) in Liberia and Sierra Leone during the 2014–2016 epidemic. Demographic and outcomes variables for 465 patients with EVD were sourced from a de‐identified, quality‐checked clinical database collected by IMC . Daily environmental temperature data for Liberia and Sierra Leone were collected from a publicly available database (Weather Underground). Mean daily environmental temperatures were averaged across each patient's ETU stay and environmental temperature thresholds were determined. Multiple logistic regression was utilised, with forward variable selection and threshold for entry of P < 0.1. Statistical significance was defined as P < 0.05. The following variables were analysed as potential confounders: age, sex, ETU , length of ETU operation and date of treatment. Results Case fatality was 57.6% among patients diagnosed with EVD . Analysis of case fatality across environmental temperature quintiles indicated a threshold effect; the optimal threshold for average environmental temperature during a patient's ETU stay was determined empirically to be 27.4 ° C (81.3 ° F). Case fatality was significantly greater for patients with average environmental temperatures above the threshold (70.4%) vs . below (52.0%) ( P < 0.001). In multiple regression, patients with average environmental temperature above the threshold during their ETU stay were significantly more likely to die than patients below the threshold ( aOR = 2.5, 95% CI 1.6–3.8, P < 0.001). This trend was observed only among patients treated in white tent ETU s, and not in ETU s with aluminium roofs. Discussion These findings suggest that an average environmental temperature above 27.4 ° C (81.3 ° F) during patients’ ETU stay is associated with greater risk of death among patients with EVD . Further studies should investigate this effect. These results have potential implications for reducing case fatality through improved ETU construction or other temperature control methods within ETU s during future outbreaks.