Looks like the WHO did warn people quite early....
https://www.who.int/dg/speeches/detail/who-director-general-s-statement-on-the-advice-of-the-ihr-emergency-committee-on-novel-coronavirus
Jan. 23rd.
"WHO’s risk assessment is that the outbreak is a very high risk in China, and a high risk regionally and globally."
"We recommend exit screening at airports as part of a comprehensive set of containment measures."
"All countries should have in place measures to detect cases of coronavirus, including at health facilities."