Diseases are another reason why some species are endangered.

A disease is an illness, sickness or ailment that affects a living thing.

https://www.zsl.org/taxonomy/term/508/wildlife-health

http://www.gbrmpa.gov.au/managing-the-reef/threats-to-the-reef/climate-change/what-does-this-mean-for-species/corals/coral-disease/coral-disease-and-its-causes

http://www.australiangeographic.com.au/blogs/australian-endangered-species/2016/01/spotted-treefrog