International Microorganism Day: facilitating global outreach events using a decentralized model

On 17 September 1683, Antonie van Leeuwenhoek, a Dutch merchant who lacked formal education and fortune, wrote a letter to the Royal Society of London describing for the first time a single-celled organism. As a tribute to this revolutionary discovery, the Portuguese Society of Microbiology with the support of the Federation of European Microbiological Societies in 2017, designated this day as International Microorganism Day (IMD), a day aiming to raise awareness about the wonderful world of microbes. Six years after the establishment of IMD, the knowledge of microbiology outreach around this celebration has expanded greatly, with 5 years of in-person and 2 years of online events. The peak of these commemorations was in 2023, with 63 parallel outreach events and more than 5000 attendees, most of which were children, and young adults. While these in-person events were occurring in the month of September, the #InternationalMicroorganismDay hashtag reached nearly 2.3 million people online, reflecting the number of users who have seen a post containing this hashtag on social media. Using a decentralized model to facilitate 63 grass-roots teams to organize events locally, IMD achieved global representation both online and offline. This paper presents details behind the organization and data on the international impact of the IMD 2022 and 2023 events, outlines plans to expand reach to more countries and audiences, and encourages readers to participate with their own events in future IMD editions so that global impact can be expanded even further.