The poultry industry is a critical source of affordable protein worldwide; however, it faces continuous threats from various poultry diseases that significantly impact public health, economic stability, and food security. Knowledge of and examination of the transmission routes, risk factors, and environmental survival characteristics of the most important pathogens affecting poultry populations, as well as the importance of strict biosecurity, are pivotal. Transmission routes are split into direct and vector-borne pathways, and indirect ways, which include infections via contaminated surfaces and vector-borne pathways, including insects and rodents. Avian influenza virus and Newcastle disease virus spread through respiratory droplets, and their transmission risk increases with increasing stocking density. While other pathogens (e.g., infectious bursal disease virus and Salmonella spp.), to persist long-term in the environments, for example, feed and litter, increasing the probability to persist long-term in the environments, for example, feed and litter, increasing the probability of infection. The long-term resilience of pathogens in multiple pathogens in various environmental conditions highlights the role of biosecurity, sanitation, and hygiene controls in preventing disease outbreaks. High stocking density in production systems, suboptimal ventilation, and inadequate biosecurity controls further increase transmission risks. This paper summarizes important disease transmissions and reinforces the need for strict biosecurity protocols and routine health monitoring to prevent the spread of pathogens within and beyond poultry facilities. These strategies can support safe poultry production, address growing global demand, and ensure food safety and public health.

Highly pathogenic avian influenza (HPAI) remains a major threat to commercial poultry. We investigated an HPAI H5N1 outbreak that became clinically apparent in House 6 of a 15-house, fully enclosed turkey breeder holding in eastern Hungary with structured site- and house-entry biosecurity. The holding contained 17,876 48-week-old birds, including 454 males in House 6. Acute mortality began on 6 February 2025 and reached 371/454 (81.7%) by 8 February; depression, lethargy, and somnolence predominated. Gross and histopathological lesions were consistent with systemic HPAI, while RT-qPCR and HA cleavage-site sequencing confirmed HPAI H5N1. A separate infected laying-hen holding was located 4.70 km away. Regional meteorological reconstruction showed directional compatibility with the inter-holding axis during 54.7% of hours from 25 January–1 February and 83.3% during 25–28 January, including a 47-h continuous compatible episode; no compatible hourly direction occurred on 1 February, when culling was completed. These findings describe a temporally and directionally compatible regional exposure context but do not demonstrate atmospheric transport, source attribution, or culling-associated transmission. Wild-bird-associated contamination and other indirect pathways remain plausible; comparative whole-genome data, environmental sampling, exact culling times, and complete trace-back information were unavailable.