Human judgment forecasts of human monkeypox transmission and burden in non-endemic countries

Background: An increase in reported human infections by the monkeypox virus (MPXV) has been observed in multiple non-endemic countries. Forecasts of transmission and disease burden associated with MPXV can support public health decision making. However, historical data that can be used to train computational forecasts is sparse. Here we show how crowdsourced human judgment can generate probabilistic predictions of the potential evolution of the international MPXV outbreak before robust computational models are prepared to provide such forecasts. Methods: We posed 8 questions associated with the monkeypox outbreak on the Metaculus forecasting platform. A total of 686 original and revised probabilistic predictions from 222 human forecasters were submitted to the forecasting platform from May 19th, 2022 to May 24, 2022. A performance based ensemble algorithm combined these individual predictions into ensemble forecasts. Findings: At time of writing, human judgment ensemble forecasts predict that the number of incident cases in the US, Canada, and Europe will continue to increase and the virus will continue to spread to multiple additional countries. Ensemble forecasts predict the World Health Organization will not declare human monkeypox a Public Health Emergency of International Concern before Dec 31, 2022.Interpretation: Human judgment forecasting is a rapid and readily adaptable approach that may improve situational awareness, synthesize available evidence, and meet public health needs as an outbreak evolves.