Nearly 80 per cent of cholera transmission in Dhaka occurred between the people who shared a household, a recent genomic study showed.
Researchers from ICDDR,B and Wellcome Sanger Institute along with other collaborators said for the first time, the transmission of cholera has been tracked at household level across Dhaka, a city with a 'hyper-endemic' level of the disease.
Dhaka is a megacity in Bangladesh that experiences two seasonal outbreaks of cholera each year. It is considered hyper-endemic for the disease.
To understand how cholera outbreaks sweep through the population and to highlight the best control strategies, the researchers tracked cholera strains at a local level - from people within households, who shared a cooking pot and ate together.
The results of the large-scale research were published in Nature Genetics on Monday.
Between 2002 and 2005, samples were taken from cholera patients admitted to Dhaka Hospital of ICDDR,B (formerly known as 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.
Once cholera entered the household it was spreading among household members, rather than repeatedly coming in from outside, within this critical time period.
This revealed that household control measures are vitally important to stop the spread of cholera.
Despite being thought of as an ancient disease, cholera cases are on the rise, with around 1.4 billion people at risk in endemic countries, and an estimated three million to five million cases each year.
The disease causes up to 120,000 deaths per year globally.
Preventing the chain of transmission within households in high-burden areas could have a huge impact on reducing the number of cholera cases worldwide.
"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," said Dr Daryl Domman, first author from the Wellcome Sanger Institute.
Reducing people's exposure to Vibrio cholera 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 help reduce cholera spread.
"Vaccination together with WASH interventions - improved water, sanitation and hygiene - are critical interventions for the prevention and controlling the spread of cholera," said Dr Firdausi Qadri, co-lead author from ICDDR,B.
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