Scientists have for the first time accurately mapped typhoid outbreaks in Nepal using Google Earth and new gene sequencing technology.
In the new research, scientists at the Wellcome Trust Major Overseas Programme in Vietnam and the Oxford University Clinical Research Units in Kathmandu, Nepal, and Ho Chi Minh City, Vietnam, combined DNA sequencing technology and GPS signalling, and mapped the data onto Google Earth.
Two bacteria -- Salmonella typhi and Salmonella paratyphi -- cause typhoid fever.
Both of these bacteria are found in Kathmandu and they usually spread through water or food contaminated with faeces. Symptoms of the disease include fever, abdominal pain and vomiting.
“Until now, it has been extremely difficult to study how organisms such as the typhoid-causing bacteria evolve and spread at a local level,” explained Dr Stephen Baker from the Oxford University Clinical Research Unit in Vietnam.
“Without this information, our ability to understand the transmission of these diseases has been significantly hampered. Now, advances in technology have allowed us for the first time to create accurate geographical and genetic maps of the spread of typhoid and trace it back to its sources,” he stated.
To capture the information, health workers would visit a patient’s home and use GPS to capture the exact location.
They would also take a blood sample from the hospitalised patient to isolate the organism and to allow analysis of the typhoid strain’s genotype -- its genetic make-up.
This genotyping used sequencing technology able to identify single changes in the ‘letters’ of DNA -- the A, C, T and Gs that make up the code.
The study showed that people living near to water spouts, for whom these provide their main source of water, and people living at a lower elevation are at substantially greatest risk of contracting the disease.
The study has been published in the journal Open Biology.
