Bats play a vital role in ecosystems around the world. They are a diverse group of animals accounting for over 20% of the world's mammals.

In the UK, bats are Indicator Species, because changes to our bat populations can indicate changes in aspects of biodiversity. For example bats might suffer when there are problems with insect populations (because our bats feed on insects) or when habitats are destroyed or poorly managed (for example, some bats only live in large woodlands).

In addition to their important roles in many environments around the world, bats have also been recognised as hosts of some viruses that can impact human health. These are called ‘zoonoses’ or 'zoonotic diseases' (human diseases originating in animals).

The transmission of a virus (or other vector of disease) from wild animals to humans is normally the result of human alterations to the environment. For example with bats, destroying their habitat (by deforestation and intensive building for example) and the intensification of livestock farming, can mean that bats are forced to live more closely to humans, livestock and pets than they would naturally. This closer contact can result in cases of spillover of a virus into human populations either directly or via an intermediate host (e.g livestock).