Life Sciences

Why an old disease may be the curse of the future

New extensively drug-resistant variants of an ancient and deadly disease – typhoid fever – are spreading across international borders. Cases have been reported in Pakistan, India, Bangladesh, the Philippines, Iraq, Guatemala, UK, US, and Germany, as well as more recently in Australia and Canada. In recent years, drug resistant and travel-associated typhoid variants have also been spreading through the African continent. Under-reporting and international surveillance gaps mean that drug-resistant typhoid is probably even more extensive than we think.

Causing fever, headache, abdominal pain and constipation or diarrhoea, typhoid is a bacterial disease. Salmonella enterica serovar Typhi – the organism behind typhoid – kills up to one in five patients if left untreated. S. Typhi spreads from person to person in water and food, which have been contaminated by faeces. As a consequence, typhoid is often associated with inadequate sanitation and water systems, as well as with poor hygiene practices.

The rapid rise of increasingly difficult to treat typhoid is a very worrying prospect. During an age of unparalleled international trade and travel, it is inevitable that any regional rise of antibiotic resistance will have global knock-on effects.

In Europe, Australia and North America extensively drug-resistant variants (or XDR strains) were travel-related. Travellers had become infected while visiting Pakistan, where a large-scale outbreak of XDR typhoid is ongoing. Having caused at least 5,274 cases in the Sindh Province since 2016, the Pakistani XDR strain is proving resistant to all commonly available antibiotics except for one: azithromycin.

The coming years will likely see further travel-related resistant cases occur throughout the world. In Britain, strong demographic and historical ties to South-East Asia mean that about 500 typhoid cases (mostly travel-associated) are reported every year. In the US, at least 309 cases occurred in 2015 with almost 80% of confirmed cases reporting a history of travel to endemic areas. In Germany, 56 cases were reported in 2018 – 96% of which were travel associated.

The return of typhoid is something of a shock to health systems in richer countries. Between the late 19th century and the 1950s, sanitary improvements, effective vaccines and antibiotics eliminated endemic typhoid from most high-income countries. But after a lifetime of relative security, the prospect of typhoid again causing death in high-income hospitals is no longer an outlandish idea.

So how did this happen? The answer is uncomfortable and tied up in the inward-looking nature of Western disease eradication campaigns over the last century. Because, contrary to popular conceptions of typhoid as a disease of the past, typhoid never really left. As our new research shows, because typhoid control often stopped at high-income borders, it became a neglected disease in other, poorer countries. This global neglect is now proving costly.

Controlling typhoid depends in part on new technologies to prevent, diagnose and treat the disease. But it is also crucial that we keep a clear eye on the past so that we are able to rewrite the policies that enabled typhoid’s resurgence – in other words, old mistakes should not be repeated.

Article originally featured in BBC News online

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