Overheating in worker bees can occur when bees are confined in their hives during hot weather without proper ventilation or access to water. Bees dying from overheating crawl about rapidly while fanning their wings. They are often wet, and their wings appear hazy. In some cases, an abnormally large accumulation of dead bees may be seen at the hive entrance.

Bees can also die from genetic faults during all stages of development, usually without exhibiting symptoms of known diseases. However, drone brood from laying workers and drone-laying queens often die with symptoms resembling EFB but in the absence of known pathogenic agents. Genetic lethality is the suspected cause of this condition.