A silent killer once confined to Latin America now has gone global. The "assassin bug" - which spreads Chagas disease - thrives in countries like Bolivia. But up to 80,000 migrants from Latin America are now living with the illness in Spain - and no one can predict who will get serious health complications.

Physical exercise has many beneficial effects on human health, including the protection from stress-induced depression. However, until now the mechanisms that mediate this protective effect have been unknown.

In a new study in mice, researchers at Karolinska Institutet in Sweden show that exercise training induces changes in skeletal muscle that can purge the blood of a substance that accumulates during stress, and is harmful to the brain.

The study is being published in the prestigious journal Cell.

Any diet will do, say researchers, if you stick to it.

All diets - from Atkins to Weight Watchers - have similar results and people should simply pick the one they find easiest, say researchers.

The study, published in the Journal of the American Medical Association, analysed data from 48 separate trials. The Canadian team concluded that sticking to a diet was more important than the diet itself.

'Late exercise starters' can still benefit greatly from starting exercising even if over 60 years. Starting regular exercise when aged over 60 can still prevent major ill health problems and dementia, recently published research suggests. 

When Joanne Drayson regularly walked her dogs in the woodland near her home in Guildford, Surrey, UK she was unaware that a tick the size of a poppy seed would infect her with a serious and debilitating disease.

"I had this strange symptom, which I can only describe as whole body rigidness. It kept recurring," she says.