Thursday 4 November 2021

The microbiological risks of flooding


A new study has assessed surface waters following 2018's Hurricane Florence and this has detailed how a new risk factor has been introduced. The research finds that large parts of the flood waters were contaminated by fecal bacteria. The origins of the pathogens was from both human and swine waste,


The concern is that disasters like flooding increases the potential level of exposure of residents and relief workers to harmful bacteria.


To make the assessment, the scientists collected surface water samples at 40 sites across eastern North Carolina. These specimens were collected one week after Hurricane Florence made landfall, during the course of September 2018.



Samples from the same locations were again collected one month after landfall. These samples were coded Phase 1 (straight after the hurricane) and Phase 2 (four weeks later).


Generally, indoor floodwater contains a higher level of gene markers corresponding to pathogenic bacteria compared with street floodwater.


The researchers tested the water samples for a variety of bacteria, focusing on pathogens hazardous to the human health. The primary focus was with Escherichia coli, as an indicator species commonly used by microbiologists to identify fecal contamination. The detection of E. coli presupposes there were other pathogens present.


The researchers also screened for the bacterium Arcobacter butzleri plus Listeria species. Other organisms targeted included bacterial species associated specifically with either swine or humans waste, which formed part of the assessment to trace detected contamination back to its source.


The most commonly found pathogen was Arcobacter. Interestingly, the presence of Arcobacter was not associated with human or swine fecal markers. This means it was unclear where the pathogen had come from.


Another conundrum was that the levels of E. coli in Phase 2 samples taken from permanent water channels were higher than the levels of E. coli recorded from the Phase 1 samples.


While further analysis is necessary, the research demonstrates the necessity for establishing a routine water quality monitoring regime during periods of natural disaster in order to establish broader baseline measures for water quality.


The research appears in the journal ACS ES&T Water, titled “Microbial Contamination in Environmental Waters of Rural and Agriculturally-Dominated Landscapes Following Hurricane Florence.”


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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