AsianScientist (Jul. 6, 2018) – In a study published in Nature Genetics, scientists have found that nearly 80 percent of the cholera transmission in Dhaka, Bangladesh, occurred between people who shared a household.
Despite being thought of as an ancient disease, cholera has resurfaced in recent years, and the number of cases are on the rise. Around 1.4 billion people at risk in endemic countries and an estimated 3-5 million cases are diagnosed each year. The disease causes up to 120,000 deaths per year globally.
Dhaka is a megacity in Bangladesh that experiences two seasonal outbreaks of cholera each year, and it is considered hyper-endemic for the disease. To understand how cholera outbreaks sweep through the population and to highlight the best control strategies, researchers at the Wellcome Sanger Institute in the UK tracked cholera strains at a local level—from people within households who shared a cooking pot and ate together.
Between 2002 and 2005, samples were taken from cholera patients admitted to the Dhaka Hospital in Bangladesh (formerly known as the International Centre for Diarrhoeal Research, Bangladesh). Over a surveillance period of three weeks, follow-up samples were taken from other members in the same household of each cholera patient. In total, 303 Vibrio cholerae samples were collected from 224 individuals across 103 households.
The researchers sequenced the genomes of all the samples to find out how the cholera strains from each person were related, then compared them with strains coming from other parts of the globe. They found that nearly 80 percent of the secondary infections were linked to the first case in that household and were reported within the first five days from that first person falling ill.
This meant that once cholera entered the household, it was spreading between household members rather than being introduced into the home from outside. Hence, household control measures are vitally important to stop the spread of cholera.
“Using genomics, we found that cholera is easily transmitted within the household. Preventing this spread within the household could enormously reduce cholera outbreaks and highlights the need for prioritising local control strategies. This could have a huge impact, not only on the individual households, but also on the entire region,” said Dr. Daryl Domman of the Wellcome Sanger Institute who was the first author of the study.
Reducing people’s exposure to V. cholerae at the household level would help to break the chain of transmission of the disease. Local interventions, including better sanitation and hygiene, water chlorination and vaccinating household members, could also help reduce cholera spread.
“Vaccination together with improved water, sanitation and hygiene are critical interventions for preventing and controlling the spread of cholera,” said Dr. Firdausi Qadri, co-lead author from Dhaka Hospital in Bangladesh.
The article can be found at: Domman et al. (2018) Defining Endemic Cholera at Three Levels of Spatiotemporal Resolution Within Bangladesh.
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Source: Wellcome Trust Sanger Institute; Photo: Shutterstock.
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