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The spread of Typhoid fever across Fiji has been tracked and mapped for the first time - identifying hundreds of minor variants of the disease-causing bacteria - in a new study with important public health implications for Pacific Islands countries facing rising extreme weather events and a warming planet, according to researchers from the Peter Doherty Institute for Infection and Immunity (Doherty Institute).

Published in The Lancet Regional Health - Western Pacific, the study combined health data, analysis and the results from a multiyear typhoid observational study, to uncover the geographic prevalence and connections between typhoid fever cases across the eastern part Fiji’s largest island, Viti Levu, which includes Fiji’s capital Suva.

The study involved a strong collaboration driven by the Fijian Government Ministry of Health and Medical Services (FMHMS), who a decade ago developed a Typhoid Taskforce to meet the rise in infections.

Typhoid fever is endemic in most Pacific countries including PNG, Fiji and Samoa, but genomic tracking of its clusters and variants is not routine in these states. 

Exposure of the Fijian population to endemic typhoid fever is a major health challenge for the FMHMS who pursue a very active program of reporting and contact tracing and follow-up of individual cases.  

Using modern genomic and informatics technologies, the research revealed previously unlinked case clusters across the island of Viti Levu, and documented waves of pathogen variants that followed cyclone and flooding events over a five-year period from 2012-2016.

Study co-lead author University of Melbourne Professor Dick Strugnell at the Doherty Institute said the evolution of Typhoid fever in Fiji involves waves of variants and infection after the arrival of high intensity cyclones that have increased with climate change.

“As global warming and rising ocean temperatures increase the intensity of cyclones and hurricanes for the region, we can expect to see the emergence of new Typhoid variants that could become resistant to the antibiotic therapies of choice.  This resistance is widespread elsewhere in Africa and Asia,” Professor Strugnell said.

“The communities in Fiji and other Pacific Islands will need to confront the infrastructure challenges that climate change will bring, including improvements to village housing, water supplies and waste management, to help limit the impact of rising sea temperatures.”

Study co-lead author University of Melbourne Doctor Mark Davies, laboratory head at the Doherty Institute said the epidemiological surveillance of 255 Salmonella Typhi strains found lower than expected rates of importation of Typhoid fever variants into Fiji from other countries.

“Our findings show that of the many typhoid strains circulating, few of these arrived to Fiji from overseas – improving our understanding of how typhoid is transmitted in Fiji and suggesting targeted local intervention strategies like contact tracing may be useful to limit the spread of Typhoid,” Dr Davies said.

“This is a great example of epidemiology and genomics working together to uncover how this widespread disease transmits through the region, offering valuable data for Pacific Islands countries to draw on when responding to outbreaks.” 

Typhoid fever is caused by Salmonella Typhi bacteria spread through contaminated food, water and close personal contact - causing high fever, headaches and gastrointestinal upsets.

Under advice from the World Health Organisation (WHO), vaccination programs are being implemented to reduce the risks of typhoid and especially drug resistance typhoid fever. 

The study was conducted by an international collaboration involving Fiji, Australia, New Zealand and the UK.

Funders: Coalition Against Typhoid through the Bill and Melinda Gates Foundation [grant number OPP1017518], the Victorian Government, the National Health and Medical Research Council Australia, the Australian Research Council, and the Fiji Ministry of Health and Medical Services.

Peer review: https://doi.org/10.1016/j.lanwpc.2022.100488