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Salmonella threat in Africa

A nastier kind of salmonella infection has emerged alongside the HIV epidemic in Africa. The finding is the first evidence that HIV might be allowing new human pathogens to evolve in immunosuppressed people.

Most people who contract salmonella get it from eating contaminated meat, leading to an unpleasant but brief gut upset. But the bacteria can escape into the blood of people with suppressed immune systems, causing a disease called invasive, non-typhoidal salmonella (iNTS) that kills in up to 45 percent of cases. It usually affects malnourished or malarial children, but is also a complication of HIV.

Chinyere Okoro of the Wellcome Trust Sanger Institute in Hinxton, England, and colleagues sequenced the DNA of iNTS samples collected in various parts of Africa, then analysed the family trees of the bacteria. The team found they nearly all clustered in one of two closely related lineages – one that arose in Malawi in 1960 and spread across eastern and central regions in the 1980s, and a second in central Africa in the late 1970s that spread in distinct waves across sub-Saharan Africa.

The timing and locations of the spread of these bacteria coincided closely with the spread of HIV across the continent, says Robert Kingsley of the Sanger Institute, one author of the study. That suggests the two events were linked (Nature Genetics, doi.org/jfw).

We need to know more about how these bacteria spread, Kingsley says. Genetic changes suggest that it may be starting to spread directly between people. This means that in adapting to HIV-infected adults, the bacterium may be evolving into a new pathogen that could spread widely among humans.

New Scientist Magazine