Here's a hypothetical, fictional scenario, which I'm sure plenty of people working in this field have nightmares about, but which hopefully paints a meaningful picture for a very important question.
I'm in a farm in Southern China on vacation, and something feels wrong. Everyone from the town seems to be gathered around a group of children and elderly who are exhibiting flu-like symptoms. But as I walk down the line, I see those who arrived earlier. They're much worse. Profuse vomiting and diarrhea, sweating, and coughing. Then one of the town medics sneezes.
My traveling partners and I cover our eyes and faces and ask where the doctors are, and we're told that they're busy in the next town over. It would seem that a concerned father of a sick boy from a neighboring town came to request urgent assistance from local doctors, and two days later the staff of the inn where he stayed began showing symptoms. My friend asks a medic where those staff are now, as all those in the group of the sick are either very young or very old. The answer is clearly some kind of euphemism for something the medic doesn't want to say.
So this mystery disease is highly contagious, progresses rapidly, and can be fatal. Looks like a potential pandemic.
We call up the World Health Organization (which doesn't seem to have a report-a-disease hotline, strangely enough). After explaining the situation and probably spending 20 minutes being redirected until finally landing at the right desk, what would they ask us to begin mounting a response?