Resolution criteria

This market resolves YES if a major outbreak of avian flu is confirmed by the end of 2027. A "major outbreak" is defined as one of the following occurring before January 1, 2028:

1. Sustained human-to-human transmission: Confirmed human-to-human transmission of H5N1 with at least 10 confirmed cases resulting from person-to-person spread (not occupational exposure to animals).

2. Significant poultry mortality event: A single outbreak affecting 10+ million birds across one or more countries, requiring mass culling operations.

3. Pandemic declaration: Official declaration of a pandemic by the WHO related to avian influenza.

Resolution will be based on reports from the CDC (https://www.cdc.gov/bird-flu/), WHO (https://www.who.int/emergencies/disease-outbreak-news/), USDA (https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/), and WOAH (https://www.woah.org/en/disease/avian-influenza/). The market resolves NO if none of these criteria are met by December 31, 2027.

Background

The current bird flu outbreak started in February 2022 and has picked up since late 2024. H5 bird flu is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows with sporadic human cases in U.S. dairy and poultry workers. Between December 2024 and March 2025, 743 highly pathogenic avian influenza (HPAI) A(H5) virus detections were reported in domestic and wild birds across 31 countries in Europe. As of May 2025, there were 70 laboratory-confirmed highly pathogenic avian influenza A H5N1 cases in the USA, with absence of human-to-human transmission confirmed.

Considerations

Experts worry H5N1 will eventually mutate into a lethal strain capable of human-to-human transmission, setting off another pandemic. However, the current public health risk is low. The distinction between the ongoing endemic circulation and a "major outbreak" is important: current activity involves widespread animal infections and occasional occupational human cases, but lacks the hallmarks of a major outbreak as defined above.