Ethnopharmacological survey, fumigation efficiency, and pharmacovigilance of plant-based medicines for respiratory disease during COVID-19 in the Democratic Republic of Congo

Background With the onset of the COVID-19 pandemic, traditional plant-based medicines used for respiratory diseases experienced an extraordinary surge in use across the Democratic Republic of the Congo (DRC), where over 80% of the population relies on traditional medicine as its primary healthcare resource. Despite widespread public usage of herbal remedies for respiratory diseases during the pandemic, no prior study has reported community survey data on COVID-19-specific plant use from Kinshasa, the capital of DRC. Objectives We report results from a community survey documenting COVID-19 traditional plant use patterns in Kinshasa (n = 500, June 2020), structured ethnobotanical interviews with traditional healers on fumigation and bath preparations, physicochemical analysis of the fumigation delivery efficiency of volatile phytochemicals, a pharmacovigilance assessment of a fatal adverse event linked to unregulated Morinda morindoides use, and an institutional analysis of the DRC Ministry of Scientific Research and Innovation Technology (MRSIT) regulatory response framework for traditional medicine candidates. Methods Mixed-methods study comprising: (i) cross-sectional online survey (n = 500, June 2020) distributed via WhatsApp and email, assessing plant species use, preparation methods, and co-administration practices; (ii) structured face-to-face interviews with members of the Association of Traditional Practitioners of Congo (Utraco) on fumigation and bath plant preparations; (iii) physicochemical profiling of volatile constituents across fumigation species; (iv) qualitative thematic analysis of caregiver testimonials; and (v) documentary analysis of MRSIT Commission institutional records. Results Ten most cited plant species included A. annua , Z. officinale , A. sativum , C. longa , E. spp., and M. morindoides . Decoctions, fumigation, and herbal teas were the dominant preparations. Utraco healer interviews identified 18 fumigation and bath species, predominantly aromatic plants with documented anti-infective essential oil constituents. Physicochemical analysis confirmed that volatile phytochemicals in these species have vapor pressure and lipophilicity profiles consistent with efficient respiratory mucosal delivery by fumigation. A four-factor pharmacovigilance model for the M. morindoides fatal adverse event identifies multi-plant combination toxicology, pediatric pharmacokinetic vulnerability, purging formulation concentration, and social media-mediated adoption without safety guidance as converging risk factors. Conclusions Our study reports widespread, predominantly complementary use of traditional plant-based medicines for respiratory disease during COVID-19 in Kinshasa. The evaluation of fumigation efficiency of these plants may provide plausible respiratory delivery of bioactive compounds, supporting their scientific validation as inhalation-based formulations. While these practices remain an important healthcare resource for most of the population, stronger pharmacovigilance, safety monitoring, and evidence-based regulation of traditional medicines during public health emergencies are still needed in DRC.