Study traces source of Haitian cholera outbreak to Nepal
Scientists in Denmark and the United States have identified the source behind the cholera outbreak in Haiti that was responsible for putting 300 000 people in hospital and killing more than 6 000. The team used sophisticated technology that can read the entire deoxyribonucleic acid (DNA) code. The findings of their study are published in the American Society of Microbiology journal MBio.
Researchers from the Translational Genomics Research Institute (TGen) in the United States and the Technical University of Denmark (DTU) used whole genome sequencing, which elucidates the billions of chemical bases in DNA. The team suggests that the peacekeepers who travelled from Nepal to Haiti in 2010 to assist the victims of the devastating earthquake that hit the Caribbean island are the source of the outbreak.
They compared the DNA of 24 cholera samples (the bacterium Vibrio cholera) from 5 different districts in Nepal with 10 samples of cholera from Haiti. According to the team, all 24 samples from Nepal matched the samples from Haiti. The report notes that some of the samples 'were almost identical'.
The researchers provide key suggestions on how to prevent future cholera outbreaks when aid from all over the world is moved to disaster areas.
'The great similarity of Haitian cholera with Nepalese cholera is based upon the highest resolution DNA methods available, and point to a probable source of this devastating disease outbreak,' explains Dr Paul Keim, head of the TGen Pathogen Genomics Division and senior molecular biologist on the study.
It should be noted that Dr Keim, who is also a professor at Northern Arizona University (NAU) in the United States, assisted the Federal Bureau of Investigation (FBI) in tracking down the source of the 2001 anthrax letters case, which killed five people. Dr Keim and colleagues used genetic tracking techniques to probe the Haitian cholera outbreak.
The scientist points out how methods were improved during the anthrax letter forensic investigation that helped cut costs in performing genome sequencing. This allowed the researchers to use this powerful technology and tackle public health issues.
Dr Keim commended TGen's collaborators at the National Food Institute in Denmark and the Nepal-based National Public Health Laboratory.
Commenting on the findings, Dr Frank M. Aarestrup of the National Food Institute, who also leads the Antimicrobial Resistance and Molecular Epidemiology Unit and is head of the World Health Organization's Collaborating Centre for Antimicrobial Resistance among Foodborne Pathogens and of the European Union Reference Laboratory for Antimicrobial Resistance, says: 'This study highlights how rapidly infectious diseases might be transmitted globally through international travel, and how public health officials need to use advanced molecular tools, along with standard epidemiological analyses, to quickly and accurately determine sources of outbreaks.'
Co-author Professor Lance Price of TGen points out that finding the source of the cholera outbreak in Haiti will help keep future outbreaks at bay.
'This effort validates the power of advanced molecular tools in investigating outbreaks of this nature,' Dr Price says. 'The goal now should be finding ways to prevent such outbreaks, perhaps through screening prior to deployment. This study is not about placing blame, it's about preventing such disasters in the future.'