Before 4 December 2024, will the World Health Organization (WHO) or US CDC report a human case of H5N1 avian influenza infection in the Western Hemisphere where sustained human-to-human transmission is the suspected cause?

H5N1 avian influenza has recently begun killing thousands of mammals in South America, and mammalian cases are being reported in cases in the US (UC Davis, Science.org, KFF News). Human cases are rare and are generally suspected to have originated from contact with infected animals, but the prospect of human-to-human transmission has health officials concerned (WHO - Influenza Monthly Risk Assessment, CDC - Avian Flu, CDC). WHO defines "sustained human-to-human transmission" as "transmitting easily from one person to the next and then further onward" (STAT). Confused? Check our FAQ or ask us for help. To learn more about Good Judgment and Superforecasting, click here. To learn more about how you can become a Superforecaster, see here. For other posts from our Insights blog, click here.