Wednesday, September 14, 2016

Environmental Transmission and the F-Diagram in LMICs

I recently published a perspective in Environmental Science: Processes and Impacts on the environmental transmission of enteric pathogens in low and middle income countries.  Its open access and available here.  I recommend you read it - not only because i wrote it - but also because it provides a detailed overview of the state of knowledge about environmental transmission.  I discuss the five most important enteric pathogens- Shigella spp., enterotoxigenic and enteropathogenic E. coli, rotavirus, and Cryptosporidium spp., how infective they are, how much people shed, and who they can infect.  I also discuss the state of knowledge about each of the major environmental reservoirs embedded in the F-diagram.  What I discovered while working on this may be obvious, but to me it was not: enteric pathogens are all completely different! Some are really infectious, others less so.  Some can grow in food and water, others can't.  Some infect household livestock, some only infect humans.  And so - obviously - how they end up in - and move through - the environment will be dramatically different too.  But, unfortunately, we frequently forgot this.  We talk about "enteric pathogens" as a single group, and we look for "diarrheal diseases" as a unifying symptom.  I think this is a mistake.  I think the characteristics of the enteric pathogens show that they are not all the same.  Although some strategies will certainly work against multiple enteric pathogens, there are no strategies that will be effective against all enteric pathogens.