Geospatial evidence of introduction of highly pathogenic avian influenza into dairy farms in the United States

Non-waterfowl abundance is significantly higher in U.S. dairy farm outbreak counties than in high-cattle-density non-outbreak counties (p<0.00001, r=-0.542) during March–May 2024.

• Why it matters: Early HPAI A/H5N1 clade 2.3.4.4b dairy introductions in the U.S. are poorly characterized, limiting targeted surveillance to prevent further spillover and amplification.
• What they did: Across 42 confirmed dairy farm outbreaks in nine states (10 March–5 May 2024), the study used geospatial mapping, case-control ecological exposure analysis, and Knox space-time cluster testing.
• The result: Knox analysis found non-random transmission dynamics across 14 of 30 threshold combinations, consistent with a single introduction in Texas followed by regional and trade-mediated amplification, implicating livestock trade, poultry litter, and contaminated milking equipment.