Good points. As is often the case with forecasting questions, the details of the resolution criteria matter quite a bit. For this question to resolve as "yes", the UK Health Security Agency must classify H5N1 as a "level 5 risk." Currently it is classified as a level 3 risk.
So, forecasters on Metaculus are predicting whether the UK Health Security Agency will raise the H5N1 risk level to level 5, which signifies human-to-human transmission.
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