An antibiotic-resistant superbug strain of typhoid has spread globally all because one strain of the bacteria, called H58, according to a new international study.
The research involved about 74 scientists across almost two dozen countries and is one of the most comprehensive sets of genetic data on a human infectious agent and paints a worrying scene of an "ever-increasing public health threat," they said.
Typhoid is contracted by drinking or eating matter contaminated by the disease and causes symptoms including nausea, fever, abdominal pain and pink spots on the chest. If the disease is left untreated, it can lead to complications in both the head and gut and could even prove fatal in up to 20 percent of patients.
While there are vaccines available for the disease, they are not widely used in poorer countries due to limited cost effectiveness, and regular strains can be treated with antibiotic drugs. However, this latest H58 superbug, is resistant to multiple types of antibiotics and now rising to become the dominant strain of the disease.
"H58 is displacing other typhoid strains, completely transforming the genetic architecture of the disease and creating a previously under appreciated and on-going epidemic," the researchers said in a statement about their findings.
Typhoid affects around 30 million people each year, says Vanessa Wong of Britain's Welcome Trust Sanger Institute, who was part of the team.
For the study, the research team sequenced the genomes of 1,832 samples of Salmonella Typhi bacteria that were collected from 63 countries between 1992 and 2013. They found that 47 percent were from the H58 strain.
According to the research, the H58 strain emerged in South Asia 25 to 30 years ago and spread to Southeast Asia, Western Asia, East and South Africa and Fiji. They also discovered a recent and unreported wave of H58 in many countries in Africa, that could indicate an ongoing epidemic.
Kathryn Holt, a scientist at the University of Melbourne in Australia who worked on the study, said multidrug resistant typhoid is caused by the bacteria picking up new resistance genes as disease strains mix and pass from person to person.
Resistance "has been coming and going since the 1970s", she said, but in the H58 strain, the resistance genes are becoming a stable part of the genome "which means multiple antibiotic resistant typhoid is here to stay".
