Epidemiological analysis of African swine fever in the European Union during 2024.

During 2024, the number of EU Member States affected by African swine fever (ASF) decreased from 14 to 13, with Sweden regaining freedom and no new Member State becoming infected. ASF outbreaks in domestic pigs in the EU declined by 83% compared to 2023, primarily due to fewer outbreaks in Croatia and Romania, although Romania notified 66% of the 333 outbreaks in the EU. Most outbreaks (78%) occurred in establishments with fewer than 100 pigs. However, an increase in outbreaks in establishments with more than 100 pigs was observed in Italy and Poland. Like previous years, there was a clear seasonality for domestic pig outbreaks, with 51% of them notified between July and September. Most of the outbreaks in domestic pigs were detected through passive surveillance based on clinical suspicion (79.4%), while fewer outbreaks were detected through enhanced passive surveillance involving systematic testing of dead pigs (14.2%) and 6.4% through tracing contacts after outbreak detection. In wild boar, the number of outbreaks notified has remained stable since 2022 (between 7000 and 8000) with a less clear seasonality than for domestic pigs, and a winter peak observed only in Hungary, Italy, Poland and Slovakia. Overall, 29% of the 23,919 wild boar carcasses found during passive surveillance activities tested positive for ASFv by PCR, representing 70.4% of the wild boar outbreaks in the EU. In contrast, around 0.4% of the 412,753 hunted wild boar tested positive by PCR, representing 28.4% of the wild boar outbreaks. While the use of serological tests performed in wild boar decreased, the number of PCR tests remained stable. Despite the reduction in the number of outbreaks in domestic pigs, the total size of the restricted zones III in the EU remained stable, with a slight increase in restricted zones II + III in 2024.