The beekeeper's hive tool carries a contamination load between colonies. Visiting an infected hive raises the load; cleaning it between hives (scorching or washing-soda disinfection) knocks it back down. A dirty tool can then seed a healthy hive on the very next visit.
tool += visited.infected ? 0.55 : 0
tool *= 1 - hygiene*0.95
P(new infection) = tool * 0.9
- Tool hygiene discipline - how thoroughly the tool is scorched/disinfected between colonies; higher values decay contamination faster after every hive.
- Second-hand equipment risk - chance that untraceable second-hand frames or boxes introduce a fresh infection independent of the tool.
- Hives in apiary - number of colonies the beekeeper rotates through; more hives means more chances for the tool to carry pathogens forward.
- Inspection pace - how quickly the round moves from hive to hive.
Real-world takeaway: American foulbrood spores survive ordinary washing, so a hive tool that isn't scorched or disinfected between colonies is one of the most common ways disease crosses an otherwise healthy apiary.