|A measure of the ‘power’ of a micro-organism to cause disease.
|A very small infectious particle containing either RNA or DNA, but never both, and only able to replicate within living cells. Despite being often confused as such, tuberculosis is NOT caused by a virus but by a bacterium.
|Vole tubercle bacillus
|Officially known as Mycobacterium microti, it causes disease in voles and other small mammals but rarely in humans. It was evaluated as a vaccine alongside BCG in England in the 1950s and found equally protective, but was not used subsequently as some of those vaccinated developed skin tuberculosis at the injection site.