The CDC's level 3 Travel Health Notice advises against non-essential travel:
Warning Level 3 (Red): Avoid all non-essential travel to this destination. The outbreak is of high risk to travelers and no precautions are available to protect against the identified increased risk.
As of February 21, 2020 the CDC has issued a level 3 travel health notice for mainland China due to the novel coronavirus.
For how many countries (part or whole) will the CDC issue a Warning Level 3 Travel Health notice before 00:00 GMT on May 15th, due to the 2019 novel coronavirus?
Determination of the answer will be made by consulting the relevant CDC noticeboard. Positive resolution requires the CDC mentioning the 2019 novel coronavirus (COVID-19) in their reasons for issuing the Level 3 Travel Health Notice.
For the purpose of this question, a "country" is any UN member state, plus the Special Administrative Regions of Hong Kong and Macau, and the island of Taiwan, which the CDC evaluates separately.
To be clear, if a warning is issued but expires before May 15, it still counts. This is a cumulative total.
ETA (10/03/2020) If the CDC issues a Level 3 continent-wide (or a multi-country regional) advisory then all the countries mentioned in the advisory should count.