There is currently an outbreak of pneumonia among chinese children. See, for example, here: https://www.standard.co.uk/news/world/mysterious-pneumonia-outbreak-china-hospitals-sick-children-b1122117.html

Thi sounds worringly similar to Covid (but also dissimilar in some ways). I wonder if this will be a global phenomenon.

As of December 31st 2023, will this mystery pneumonia spread beyond China in a significant way? I will resolve this question as yes if more than 1000 confirmed or highly likely confirmed cases exist (or have existed between now and then) outside of China on the resolution day.

EDIT from Dec 5 for clarification, as requested in the comments:

This market specifically concerns a mysterious pathogen, like covid would have been in its early days. This market does not concern existing viruses such as RSV, because that is hardly mysterious.

I understand that the "mysterious" pathogen may be a mutation of an existing pathogen (like covid was). This obviously counts, if there has been a substantial mutation (like covid was). Minor mutations (like the constant minor changes to the seasonal flu) dont count. For example, let's assume that the "mystery pneumonia" is an RSV outbreak. That would not count, unless it turns out to be a novel Super-RSV with substantially higher mortality/infectiousness/whatever,

Also, this question pertains to the specific mystery pneumonia observed in China, wherever it may be from. Only this one counts. If this pathogen is originally from a different country and spreads from there, it counts because its still the pathogen that this question is about. If it turns out that there is a second mystery pneumonia that has nothing to do with the current outbreak in China but still spreads globally, it does not count (because this question is about the present outbreak in China).