Zoonotic diseases are infections that transfer from animals to people, and include killers such as bubonic plague, malaria, ebola and a whole host of others. Trying to understand how diseases make the leap from animals to humans – so called spillover – and how outbreaks occur is a crucial part of preventing them. But outbreaks are complex and dynamic, with a huge number of factors playing a role: What animal is hosting the disease, the environment in which it lives, the changing climate, human presence and impact on the local area and many other factors. Kate Jones is professor of ecology and biodiversity at University College London, and has been tracking ebola in Africa. Her team has just published a new study that models how and when spillover might happen in the future. On the lushly forest islands of French Polynesia, there lives a very special snail. Partula are around 100 species of tiny snails who give birth to live young and feed on decomposing plants. Each species is uniquely adapted to a particular ecological niche. But in 1967, the highly edible Giant African Land Snail was introduced to the islands as a source of food. They quickly became pests, and in response, the French Polynesian government then introduced carnivorous Rosy Wolf Snails - aka Euglandina rosea - to quell the spread of the introduced Giant Land snails. Reporter Naomi Clements-Brode picks up the story with scientist Ann Clarke, along with Dave Clarke and Paul Pearce-Kelly at ZSL London Zoo. Finally this week, malaria is, as best we can account for it, the single greatest killer in human history. The vast majority of malaria is caused by a type of single celled protozoan called Plasmodium falciparum, carried by mosquitos. But according to new research published this week, it started out around fifty thousand years ago not in us, but as a gorilla disease, and in one particularly unlucky gorilla, two simultaneous infections prompted the mutation and rise of the plasmodium parasite that would go on to kill millions. Dr Gavin Wright from the Wellcome Sanger Institute in Hinxton lead the team behind this molecular archaeology.