Health experts are warning that antibiotic-resistant typhoid has spread around the globe and that the silent epidemic is becoming an ever increasing threat.
In a new study which involved collaboration from 74 experts in 24 countries, the authors discovered that a strain of antibiotic-resistant typhoid has swept across Africa and Asia in the last 30 years.
Calling for "global surveillance" against the disease, the paper, published today in the journal Nature Genetics, shows the genetic architecture of typhoid strains has been changing over the decades, with an antibiotic-resistant strain becoming more prevalent. This strain is replacing those that were previously treatable with antibiotics.
"Typhoid affects around 30 million people each year and global surveillance at this scale is critical to address the ever-increasing public health threat caused by multidrug resistant typhoid in many developing countries around the world," says Dr Vanessa Wong, one of the report's authors from the Wellcome Trust Sanger Institute in the UK.
Looking at bacteria samples from 63 countries, the authors found 21 had the H58 strain.
The study found that a single strand of typhoid bacteria, called H58, is responsible for all antibiotic-resistant typhoid cases.
Rather than preventing infection with vaccinations, typhoid is typically treated with antibiotics in the countries suffering epidemics. As it spreads to new populations, the H58 strain has developed mutations, making it resistant to different types of antibiotics, explained Dr Kathryn Holt, from the University of Melbourne.
"Multidrug resistant typhoid has been coming and going since the 1970s and is caused by the bacteria picking up novel antimicrobial resistance genes, which are usually lost when we switch to a new drug," she said.
"In H58, these genes are becoming a stable part of the genome, which means multiply antibiotic resistant typhoid is here to stay," she added.
According to the World Health Organization, an estimated 21 million people are infected with typhoid each year, of which 222,000 die. Symptoms include fever, high temperature, stomach pains and diarrhea. It is caused by the bacteria Salmonella typhi, which is related to Salmonella bacteria which causes food poisoning.
