Reporting trends and seasonality in the World Health Organization's Disease Outbreak News (DONs) across 1996-2023.

The Disease Outbreak News (DONs), which are published by the World Health Organization, are used in outbreak surveillance, management and research as official reports of disease outbreaks worldwide. This study analyzed datasets of the DON created by Carlson et al. (2023) and Weets et al. (2025) to understand reporting behavior in DONs published across 1996-2023. Time series analysis was conducted by disease transmission group and geography. Interrupted time series analyses were conducted to investigate changes in reporting behavior before and after the 2003 SARS-CoV-1 outbreak, and before and during the COVID-19 pandemic. We observed an annual, 12-month seasonality in reporting across all DONs. By disease transmission group, Airborne and Droplet transmission-related DONs and Vector-borne transmission-related DONs exhibited 12-month seasonality in reporting. Faecal-oral and FWB transmission-related DONS exhibited 9-month seasonality in reporting. Findings from our interrupted time series analyses revealed that during the COVID-19 pandemic, reporting across all DONs decreased, with a step-change difference of -3.73 reports at baseline comparing negative binomial regression models before and during the pandemic. In addition, after the 2003 SARS-CoV-1 outbreak, reporting of Airborne and Droplet transmission-related DONs increased, with a step-change difference of 3.77 reports at baseline comparing negative binomial regression models before and after the outbreak. As a collection of press releases which are selectively published by the WHO, the DON is not a complete representation of global disease outbreaks, and researchers should be aware of these reporting patterns and biases when using the DONs in outbreak surveillance and global health research.