A major outbreak of typhoid fever in Pakistan may have been caused by a highly drug-resistant superbug, scientists have warned.

Research by the Wellcome Sanger Institute has shown that the typhoid strain behind the outbreak, which began in Hyderabad in November 2016 and has since spread, has acquired an extra piece of DNA that renders it resistant to multiple antibiotics.

“It is significant because it marks the first time we have seen such high levels of drug resistance in typhoid,” said Elizabeth Klemm of the Wellcome Sanger Institute, who co-led research carried out in collaboration with Public Health England and Aga Khan University in Karachi. “Increasing drug resistance means we have fewer drugs available to effectively treat the infection.”

Typhoid fever is a bacterial infection caused by the bacterium Salmonella enterica serovar Typhi. The bacteria, spread by contaminated food and water, is highly contagious, and spreads through communities with poor sanitation. Symptoms include fever, stomach pain, headache and constipation or diarrhoea. If left untreated, the infection can be fatal.

There is no official information available on case numbers or deaths in Pakistan, but local media reports claim more than 800 cases of drug-resistant typhoid were detected in Hyderabad alone over a 10-month period between 2016 and 2017. An emergency vaccination campaign is now under way.



“There have been cases in Sindh province and other parts of Pakistan,” said Klemm. “One case was found in the UK from a patient who had recently been in Pakistan.”

The Cambridge-based Wellcome Sanger Institute was approached by scientists at Aga Khan University last spring with a request for genetic analysis of samples. It emerged that the H58 strain, previously linked to drug-resistant cases, was behind the outbreak. Further analysis revealed the strain had gained an extra strand of bacterial DNA – a plasmid – that increased its resistance to antibiotics. The results were published in the scientific journal mBio.

Charlie Weller, head of vaccines at the Wellcome Trust, a London-based biomedical research charity, said the findings were a clear warning that “treatment options for typhoid are running out” and focusing on prevention was now vital.

“We have seen other resistant typhoid strains spread globally in the past,” said Klemm. “We have the ability to prevent typhoid by vaccination and improving water, sanitation and hygiene. A new typhoid vaccine has been recently approved by the World Health Organization. The increased levels of drug resistance in typhoid add urgency to the call for vaccination.”

The US Agency for International Development has backed a vaccination drive in Sindh by donating 250,000 syringes for a campaign to immunise children in two towns in Hyderabad, Latifabad and Qasimabad.