Cholera and severe toxigenic diarrhoeas

Vibrio cholerae O139 genomes provide a clue to why it may have failed to usher in the eighth cholera pandemic

Cholera is a life-threatening infectious disease that remains an important public health issue in several low and middle-income countries. In 1992, a newly identified O139 Vibrio cholerae temporarily displaced the O1 serogroup. No study has been able to answer why the potential eighth cholera pandemic (8CP) causing V. cholerae O139 emerged so successfully and then died out. We conducted a genomic study, including 330 O139 isolates, covering emergence of the serogroup in 1992 through to 2015. We noted two key genomic evolutionary changes that may have been responsible for the disappearance of genetically distinct but temporally overlapping waves (A-C) of O139. Firstly, as the waves progressed, a switch from a homogenous toxin genotype in wave-A to heterogeneous genotypes. Secondly, a gradual loss of antimicrobial resistance (AMR) with the progression of waves. We hypothesize that these two changes contributed to the eventual epidemiological decline of O139.

Vulnerability to coastal cholera ecology

The battle to completely control cholera continues. Multiple strains, high levels of morbidity in some regions of the world, and a complex of influences on its distribution in people and the environment are accompanied by only rough resolution prediction of outbreaks. Uncertainty as to the most effective array of interventions for one of the most researched infectious diseases thwarts further progress in providing cost-effective solutions. Progress on the research front consistently points towards the importance of disease ecology, coastal environments, and the sea. However, evaluation of the link between cholera in people and environment can only be effective with analysis of human vulnerability to variable coastal cholera ecologies. As there are some clear links between the organism, cholera incidence and the sea, it is appropriate that cholera research should examine the nature of coastal population vulnerability to the disease. The paper reviews the cholera risks of human-environment interactions in coastal areas as one component of the evaluation of cholera management. This points to effective intervention through integrative knowledge of changing human and environmental ecologies, requiring improved detection, but also an acceptance of complex causality. The challenge is to identify indicators and interventions for case specific ecologies in variable locales of human vulnerability and disease hazard. Further work will therefore aim to explore improved surveillance and intervention across the socio-behavioural and ecological spectrum. Furthermore, the story of cholera continues to inform us about how we should more effectively view emergent and resurgent infectious disease hazards more generally.

Health ecology and environmental management in Mozambique

A health ecology approach to infectious disease incidence recognises that the weighting and interconnectivity of influences on health vary in terms of nature and context, from place to place and over time. It helps explain inherent limitations in the prediction and management of major infectious disease events and consequently why victims of ill health and policy often lack appropriate strategies for disease avoidance and health disaster mitigation. With reference to ongoing research in Mozambique, the paper uses the approach for assessment of health insecurity and to provide a realistic framework for management of complex disease hazards.