Yes, ENDEMICS is a Scrabble word!

Letter values in Scrabble US: E 1, N 1, D 2, E 1, M 3, I 1, C 3, S 1.

Is it a valid word?

ENDEMICS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location
a plant that is native to a certain limited area

Also: endemic disease.