Lesson 62: Viruses

Deformed wings, shaking bees and black queen cells: what viruses do, and why mite control is virus control

Honey bees carry many different viruses, around 20 described from symptoms, and more found with modern DNA tests. Most virus infections cause no problems in a healthy colony without chronic stress. Viruses become dangerous when something else, above all varroa mites, lets them build up.

There are no medicines for any honey bee virus. What you can do is keep colonies strong and keep mites down.

The viruses you're most likely to see

Deformed wing virus (DWV)

• The one you'll see most. Spread and made far worse by varroa mites (lesson 54): mites inject the virus as they feed on pupae, and uncontrolled mite populations are the main driver of DWV.
• Signs: young bees with shriveled, crumpled, useless wings ("string wing"), sometimes shortened abdomens. They die soon after emerging.
• If you see deformed wings, do a mite count right away (lesson 55). Even if the count isn't high at that moment, mites and DWV were almost certainly both involved.

Parasitic mite syndrome (PMS)

Not one virus but a set of symptoms in colonies with heavy mites and viruses: - spotty brood; larvae sunken or slumped in cells, sometimes looking melted or "snotty"; - uncapped cells with chewed pupae, some with their heads chewed off; - bees with deformed wings; - a small, dwindling adult population.

PMS can look like foulbrood (lessons 58–59). A high mite count points to PMS, though colonies can have more than one problem.

Sacbrood virus

Covered in lesson 60: larvae stretched out in a fluid-filled "sac", head curled up.

Paralysis viruses (chronic and acute)

• Two viruses that beekeepers can't easily tell apart.
• Signs: shaking, trembling bees that can't fly, often crawling on the ground or up grass stems in front of the hive; bees that look bald, shiny and greasy ("hairless black syndrome"); sometimes bloated abdomens and wings held oddly. Guard bees nip and harass them at the entrance, which can look like robbing (lesson 50). Sick bees die within a few days.
• Spread mainly by body contact between bees. Bees differ genetically in how susceptible they are, so requeening is a good step if you see it.
• Other causes of shaking, paralyzed bees have been suggested too, including some plant nectars and pollens, poor pollen supply in early spring, and fermented stored pollen.

Black queen cell virus (BQCV)

• Affects queen larvae and pupae: they die after the cell is sealed, and the queen cell turns dark or black. You'll notice it mostly when raising queens (lesson 79).

How it looks: Deformed wing virus: a young worker with crumpled wings.

Deformed wings and a varroa mite on the same bee. The mite spreads the virus.

How viruses spread

Viruses pass from drone to queen during mating, from queen to egg, from nurse bees to larvae in food, between workers when they share food, and through contaminated food and flowers. They can also move between honey bees and other bees and insects nearby. Varroa mites are the most important carrier.

Stress makes viral infections worse. Examples include heavy mites, poor nutrition, and pesticide exposure (some pesticides, and even some miticides such as amitraz, have been linked to higher virus levels).

What you can do

There is no treatment for viruses themselves, so everything is about prevention:

1. Control varroa (lessons 54–56). This is the single most important step.
2. Use resistant stock: Russian and Varroa Sensitive Hygiene (VSH) bees have been shown to suppress viruses as well as mites (lessons 15, 83).
3. Requeen colonies showing virus symptoms (lesson 45).
4. Reduce spread between colonies:
5. don't crowd too many colonies into one yard;
6. space hives apart, face them different ways, or mark them differently to reduce drift;
7. don't move frames from a colony with symptoms into another colony;
8. clean your hive tool with alcohol after working a colony with symptoms.
9. Good nutrition: make sure bees have varied pollen; feed when forage is poor (lesson 39).
10. Replace old comb: about a third of the frames each year (lesson 53).
11. Encourage propolis: bees coat rough inside surfaces with propolis, which has been shown to boost their immune response and lower virus levels (lesson 76).
12. Limit pesticide exposure (lesson 68).

Testing for viruses needs laboratory DNA methods that aren't generally offered to the public, so you'll judge mostly by symptoms and mite counts.

What to remember

• Most viruses are harmless in a healthy colony. Varroa turns them dangerous.
• Deformed wings = mite problem. Count mites now.
• PMS: spotty brood, slumped larvae, chewed pupae, deformed wings, dwindling bees, high mites.
• Paralysis: shaking, bald, greasy bees that can't fly.
• No medicines. Control mites, resistant stock, requeen, good food, new comb, clean tools.

Quick check

1. You see several young bees with crumpled wings. What should you do first?
2. Name three signs of parasitic mite syndrome.
3. Why can bees with paralysis virus be confused with robbing?

Show answers

1. Do a mite count; deformed wing virus is spread and made worse by varroa, so mite control is the fix. 2. Any three of: spotty brood; sunken or melted-looking larvae; uncapped cells with chewed pupae; bees with deformed wings; a dwindling adult population; high mite counts. 3. Sick bees look bald, shiny and greasy, and guard bees chew and harass them at the entrance, just as they would robbers.

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Adapted from: Penn State Extension, Viruses in Honey Bees (Grozinger, Underwood & López-Uribe, updated January 2026) and A Quick Reference Guide to Honey Bee Parasites, Pests, Predators, and Diseases; UGA Bee Program, Honey Bee Disorders: Viral Diseases and Honey Bee Parasites; Honey Bee Health Coalition, Identifying and Mitigating Foulbrood (2022).

Photos: DWV worker, Xolani90, CC BY-SA 3.0 · DWV with varroa, Stefan de Konink, CC0 (both via Wikimedia Commons).

Adapted from university Extension sources. Experienced Georgia beekeepers are reviewing these lessons. See something that doesn't match your experience? Tell us.