Honey bees, like all social creatures, are hosts to a wide array of bacteria, viruses, fungi, and parasites that can compromise their health. While a bee colony is a complex ecosystem where pathogens constantly circulate, the resulting infections are overwhelmingly a threat to the bees themselves, not to humans. Beekeepers must manage serious microbial threats, but the average person has little cause for concern regarding direct disease transmission.
Do Bees Transmit Diseases to Humans?
Bees are generally not considered vectors for human disease, especially when compared to insects like mosquitoes or ticks. The vast majority of diseases that afflict honey bees, such as Deformed Wing Virus or American Foulbrood, are species-specific and pose no risk to humans. The World Organisation for Animal Health confirms that none of the honey bee diseases it monitors are infectious to people.
The one area of overlap involves Clostridium botulinum spores, which can be found in raw honey. These spores are a soil-borne contaminant that bees inadvertently collect, not a pathogen that infects the bee itself. While harmless to adults, these spores can cause infant botulism in infants under one year old. This is a food contamination risk, not a disease transmitted directly from the bee as a biological vector.
Major Pathogens That Threaten Bee Colonies
The most severe threats carried by bees are those that devastate colony health, often targeting the vulnerable brood. Among viral diseases, Deformed Wing Virus (DWV) is the most widespread, frequently associated with high levels of Varroa destructor mites. The virus causes symptoms in emerging bees, including shrunken and crumpled wings, which limits their ability to forage and contribute to the colony.
Bacterial infections are a major concern, particularly American Foulbrood (AFB), caused by the spore-forming bacterium Paenibacillus larvae. This disease is highly destructive because its spores can remain viable for decades in honey and beekeeping equipment, making eradication difficult. Another bacterial threat is European Foulbrood (EFB), caused by Melissococcus plutonius, which infects the gut of young larvae before their cells are capped. EFB is less severe than AFB but can still weaken a colony substantially.
The most significant parasite impacting honey bees is the external mite, Varroa destructor. These reddish-brown parasites feed on the fat body tissue of both adult bees and developing brood, weakening the bees and shortening their lifespan. Varroa mites act as a mechanical vector, transmitting and amplifying viruses like DWV throughout the hive. The microsporidian Nosema is an internal parasite that affects the midgut of adult bees, leading to dysentery, reduced lifespan, and poor colony performance.
How Diseases Spread Within and Between Hives
The highly social nature of a honey bee colony is the primary mechanism for the rapid spread of pathogens within the hive. One common route of transmission is trophallaxis, the act of food-sharing between worker bees, which allows viruses and bacterial spores to circulate throughout the adult population. Nurse bees also spread diseases like foulbrood when they clean out or feed contaminated cells to new generations of larvae.
The transmission of disease is not limited to direct contact, as pathogens also spread through vertical and mechanical routes. Some viruses can be passed vertically from the queen to the egg, ensuring the infection is present in the colony from its inception. Mites like Varroa act as mechanical vectors, physically carrying virus particles from one bee to the next as they move and feed on the bees’ hemolymph.
Between colonies, infection often occurs through resource-based interactions. “Robbing” is a behavior where bees from one hive steal honey from a weaker, often diseased, neighboring hive, inadvertently carrying back spores and microbes. Similarly, “drifting” bees, which mistakenly enter a hive other than their own, can introduce new pathogens. Contaminated beekeeping equipment, such as frames or tools, acts as a significant mechanical bridge for the dispersal of resilient spores and viruses across entire apiaries.