Can there be "an" "endemic"? (Can "endemic" legitimately be used as a noun?)

I agree that this was likely an error for epidemic. However, in a biological context (different field of biology than medicine) "an endemic" is often used to refer to an organism that is endemic to a particular area. Thus, "Species X is an endemic here." Or, "This island has many endemics" as a shorthand for "...many endemic species."

Endemic as an adjective means regularly found in a specified population. Its use as noun means an endemic disease. The OED finds this usage from 1662 and quotes The Saturday Review (1859) for a figurative use thusly:

Snobbishness in an insidious endemic.

For a literal use, we may consult An outline of the history and cure of fever, endemic and contagious by R Jackson (1798)

... while contagious fever, occasionally exposed to pure air often intermits or remits like an endemic;....

The noun usage seems as dated as Jackson's medical advice though.

One more example by request, from Medical Record, Volume 35 (April 6, 1889), G F Shrady and T L Stedman eds.

Only within the last twenty years, after the attention of medical men had been drawn to repeated observations of endemics and epidemics of pneumonia,....

So, this site https://www.vocabulary.com/dictionary/endemic seems to offer a noun form that, albeit used infrequently, would fit the usage by the AMA author that first caught my eye.

I see that this was also explained by someone above, but somehow it didn't sound convincing given the context! This does:

"Endemic n 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

Synonyms: endemic disease"

Ironically, the AMA writer copied the term directly from an editorial by a physician-writer and dean of a medical school, someone with whom I have worked on articles, and who seems to be a stickler for proper usage! Like me, probably had a schoolteacher mother...

Anyway, thanks everyone for considering with me!