1 Oct 2012

Deadly salmonella strain piggybacks on HIV

4:15 pm on 1 October 2012

An epidemic of a deadly strain of salmonella has swept across the whole of Africa by "taking advantage" of the spread of HIV, according to an international team of researchers.

Their study, published in Nature Genetics, is the first to identify the separate cases as a single epidemic.

It is thought to be the first time a single strain of an infection has spread so widely in the wake of HIV. One in four people in Africa infected with it have died.

Cases of this form of invasive non-typhoidal salmonella have been recognised in Africa for more than a decade, the BBC reports. It causes fever, headaches, respiratory problems and sometimes death.

The research team analysed the genetic code of 179 batches of salmonella from different parts of Africa and the rest of the globe. Using techniques similar to a large-scale DNA paternity test, they were able to construct the strain's "family tree" and then how it spread.

It happened in two waves. The first started in south-eastern Africa about 52 years ago and the second 35 years ago from the Congo Basin.

Gordon Dougan, of the Sanger Institute in Cambridge, Britain, says: "It quite clearly parallels the emergence of HIV in Africa."

'It's got a grip in Africa'

HIV attacks the immune system and leaves people more vulnerable to other infections. It is thought the salmonella strain took advantage of this weakness to spread.

There is poor monitoring data for the disease across the whole of the continent, but Professor Dougan says it's affecting "thousands and thousands" of people and that 98% of adult cases are in people with HIV.

Commenting on the study, Brendan Wren of the London School of Hygiene and Tropical Medicine told the BBC: "It's actually quite a huge problem and it seems to be getting worse because there are many susceptible people. It's got a grip in Africa."

However, Professor Wren thinks the disease is "near its peak" because HIV is more controlled in other continents, giving the salmonella strain little room to spread.