Vancouver Island Puzzled by Rare Cholera Outbreak


Four human cases of cholera have been identified on Vancouver Island, an island on the western coast of British Columbia, Canada[1]. The outbreak was first reported the week of March 25th, 2018. The cases have been linked to consumption of herring eggs [2] that were harvested on the coast of the island [3]. This string of cases has surprised health officials because cholera is rare in Canada; only seven cases of cholera throughout the country have occurred in the last five years, all of which were imported from cholera-endemic countries [4].


Cholera is disease caused by the bacteria Vibrio cholerae and is spread by ingesting contaminated food or water. The infection is usually mild, but can be severe and life threatening. Symptoms of cholera can include extreme watery diarrhea, vomiting, rapid heart rate, muscle cramps, and low blood pressure. If untreated, symptoms can result in severe dehydration, which can rapidly lead to shock and death within hours [10].


One theory for the origin of the outbreak on Vancouver Island is that approximately 17 billion liters of untreated sewage and waste water had been dumped off the coast of Vancouver, B.C., which is located near Vancouver Island [5]. This exposure to water containing fecal matter may have contaminated the herring eggs, and marine water sampling from the area this past month showed elevated levels of fecal coliform [8]. However, the outbreak has largely stumped health officials as to the source; herring eggs have been harvested off the island for decades, and an outbreak has never occurred before [6].


Since the notification of the outbreak, the Department of Fisheries issued a closure notice to herring egg harvesting in the area where the cases were reported [7], and the herring egg fishery in the area has been temporarily closed [11]. Since the initial cluster of cases in March, no additional cases have been reported. [9]. 

















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