CDC staff ordered to stop working with WHO immediately

The CDC has been instructed to cease collaboration with the World Health Organization (WHO) as it monitors bird flu outbreaks in US livestock. This directive follows President Donald Trump's executive order to initiate the US withdrawal from the WHO, a process that requires Congressional approval. Dan Grossman from Script News reports on the situation.

How does the CDC's order relate to the current situation with bird flu among US livestock?

What is required for the US to officially withdraw from the World Health Organization?