Claim: Scientists knew about the new coronavirus long ago and called it "Disease X".
Fact-check: The World Health Organisation did not know about the Covid-19 virus before the current outbreak - Full Fact
Verdict: they didn't. this is a misunderstanding about the phrase "disease x", which the who used to denote an unknown serious new disease that might cause a pandemic.
Organisation: Full Fact
Author: Leo Benedictus
Date published: 2020-02-18T00:00:00