Deformed wing virus

Deformed wing virus, usually known by its acronym DWV, is the most widespread virus of the honey bee. It is found in the vast majority of colonies, most often without any symptoms. Combined with varroa, it becomes one of the leading causes of colony collapse worldwide, especially in late autumn and winter.

For beekeepers, DWV has one defining feature: it cannot be cured. There is no antiviral medicine for bees, and all control relies on managing the mite that transmits it. This factsheet describes the virus, then what to do when bees with crumpled wings appear.

What DWV is

DWV is a small positive-sense, single-stranded RNA virus with a genome of around 10,000 nucleotides. It belongs to the genus Iflavirus, in the family Iflaviridae, a group of viruses that infect insects².

The virus is present on almost every landmass where honey bees live. Australia is the exception^{4, 13}, which is explained by the historical absence of Varroa destructor there. Genetic analyses show that the current epidemic is recent and originated in the European honey bee. Bee populations in Europe and North America drove its spread, through trade and the movement of colonies¹.

Variants: DWV-A, DWV-B and others

Several main variants, sometimes called genotypes, are recognised:

• DWV-A is the historical form, long the most common.
• DWV-B was described in 2004 from mites collected in the Netherlands, under the name Varroa destructor virus-1 (VDV-1). Its sequence differs from DWV-A by about 16%⁴.
• DWV-C was identified in the United Kingdom in 2016. It is rarely reported and its impact is poorly known^{4, 13}.
• DWV-D was recovered from Egyptian honey bees collected in the 1970s; it has not been reported since⁴.

The rise of DWV-B

DWV-B is spreading rapidly worldwide. According to a 2022 review, in Germany DWV-B was already present in almost all sampled colonies in 2013, while the share of colonies carrying DWV-A fell sharply between 2013 and 2020. DWV-B also became predominant in the United Kingdom during the 2010s, and its share rose strongly in north-eastern Italy⁴.

In the United States the change appears less advanced, but the share of DWV-B is also increasing in published data. The authors cautiously describe a possible replacement of DWV-A by DWV-B worldwide⁴.

Is DWV-B more dangerous? Results differ. A field study first suggested it was relatively benign and could protect colonies against the more virulent form¹⁰. Experiments on adult bees then showed it replicates faster; results on pupae are contradictory. The 2022 review concludes that its virulence is probably equal or somewhat higher, while noting the lack of whole-colony experiments⁴. Whatever the variant, it is varroa that turns a discreet infection into disease.

How the virus spreads

Routes without varroa

The oral route. The virus circulates in contaminated larval food, through food sharing between adults (trophallaxis) and through cannibalism of infected pupae⁴. This route usually leads to low-level infections without symptoms.

The venereal route. Drones can carry the virus in their semen. Experimental work has shown that the queen can be infected during mating, and that the virus can then reach her tissues, including the ovaries and spermatheca⁶.

The vertical route. The virus has been detected in both unfertilised and fertilised eggs: it passes from the queen and drones to their worker and drone offspring^{5, 6}. This route keeps the virus in colonies, with no visible sign.

The varroa route

Varroa changes everything. By feeding on pupae in capped cells, then on adults, it injects the virus straight into the bee’s body. The mite then carries the virus from bee to bee, and from colony to colony through drifting and robbing, particularly in autumn⁴. Whether the virus also replicates inside the mite is still debated.

The most telling observation comes from Hawaii. After varroa arrived in the archipelago, the proportion of bees carrying DWV rose from about 10% to 100%, the viral load per bee increased by a factor of around a million, and strain diversity collapsed in favour of a single dominant strain³. Varroa does not merely spread the virus: it selects the forms that are best transmitted through it.

Why it matters

In pupae: deformed wings and doomed bees

When a pupa receives a high dose of virus during development, typically via varroa, it may emerge with crumpled, stunted or stubby wings, a shortened abdomen and a smaller body^{2, 13}. These bees never fly and die soon after emerging, often after being thrown out by their nestmates.

The damage adds to that caused by the mite itself. Varroa feeds mainly on the bee’s fat body, the organ that stores reserves, contributes to immunity and determines the longevity of winter bees¹².

In adults: learning, foraging and lifespan

The virus does not only affect development. In foragers, experimental DWV infection impairs olfactory learning: infected bees are worse at associating an odour with a sugar reward and retain that association less well⁷.

Covert infections

Covert, or latent, infections in normal-looking bees are the most common form of DWV¹³. They are not harmless. One study used electronic tags (RFID) to follow workers given a low dose of virus: they died more often, started foraging younger and had shorter foraging careers⁸.

At colony level: autumn and winter collapse

The varroa population peaks in late summer, exactly when the colony is rearing its winter bees, which must live for several months. If these bees are parasitised and infected during development, they live much shorter lives. The colony then dwindles in late autumn or winter, often with intact stores and few dead bees in the hive. This is a common picture in winter losses.

Beyond the honey bee

DWV has been detected in many other flower-visiting insects: bumblebees, wild bees, wasps, hoverflies, beetles and ants^{4, 13}. In the United Kingdom, a study showed that bumblebees and honey bees living in the same area carry the same virus strains, indicating ongoing transmission between them⁹. The real impact on wild populations remains to be established, but a heavily infested colony is also a source of virus for its surroundings.

Recognising DWV

Symptoms

• Crumpled, wrinkled, stunted or stubby wings in young bees.
• Shortened or bloated abdomen, smaller body, abnormal colouring¹³.
• Bees unable to fly, walking on the frames or in front of the hive, then expelled.
• Visible mites on adults; patchy brood with dead pupae.
• Colony dwindling in September-October even though stores are present.

Do not confuse

Diagnosis

In the apiary

In the field, young bees with deformed wings combined with a heavy varroa load are, in practice, enough to conclude. The decisive step is measuring the varroa load: take about 300 bees from an open brood frame (queen set aside), do an alcohol wash or sugar roll, and calculate mites per 100 bees. The detailed method and thresholds are in the Varroa mites and varroosis factsheet.

In the laboratory

The virus is usually confirmed by RT-PCR, which detects viral RNA, or by ELISA¹³. Quantitative PCR techniques can measure viral load and distinguish variants. The virus can be detected at every stage: eggs, larvae, pupae, workers, drones and queens.

These tests are mainly used for research and surveillance. For an individual colony they rarely change the decision, since the virus is present in most hives. In case of unexplained losses, contact your local bee health organisation or a veterinarian.

Regulations

In France, deformed wing virus is not a notifiable bee disease. Control relies on managing varroa with authorised veterinary medicines, recorded in the apiary treatment register.

Status varies between countries. In the United States, DWV is a “monitored” disease, reported monthly to federal veterinary services. It is not listed by the World Organisation for Animal Health (WOAH)¹³.

Prevention and control

No antiviral treatment: control varroa

No medicine destroys DWV in a colony. The only effective strategy is to control varroa: monitor regularly, treat as soon as the harvest is over to protect winter bees, treat every colony in an apiary at the same time, check efficacy with a follow-up count, and add a broodless winter treatment if needed. Methods and medicines are covered in the Varroa mites and varroosis factsheet.

Also limit the circulation of the virus: no collapsed colonies left open to robbing, reduced drifting, no colonies of unknown origin introduced without checks. See the Apiary biosecurity factsheet.

What research is preparing

RNA interference. Laboratory work has shown that feeding larvae or adults double-stranded RNA targeting DWV reduces viral load, limits wing deformities in exposed larvae and extends adult survival¹¹. In the United States, a double-stranded RNA product has recently been registered, but it targets varroa, not the virus. No RNA-based antiviral is available to beekeepers.

Breeding. Selecting bees that limit varroa reproduction, for example through varroa-sensitive hygiene (VSH), indirectly reduces viral pressure. But no current line removes the need to monitor and treat.

Most common mistakes

• Looking for a treatment against the virus instead of treating varroa.
• Waiting for deformed wings before acting: by the time they appear, the infestation is already high.
• Treating too late, in September or October, when winter bees are already affected.
• Treating only the sick colony and letting the others in the apiary reinfest it.
• Assuming a colony without symptoms is free of the virus: it is almost always present, in covert form.

Frequently asked questions

Can a bee with deformed wings recover? No. Wings form at the pupal stage: a bee that emerges with deformed wings will never fly. The goal is to protect the bees still developing.

Is honey from an affected colony safe to eat? Yes. DWV is an insect virus: it does not infect humans. Treatments, however, must be applied without supers and according to the label.

Can bees have deformed wings without varroa? It is possible, since the virus is also transmitted through food and by the queen. But in numbers, visible cases are almost always linked to varroa: count mites before looking for another cause.

Does DWV-B change how to fight it? No. Whatever variant dominates in your area, the approach is the same: monitor varroa and keep it low, especially while winter bees are being reared.

References

1. Wilfert L., Long G., Leggett H.C., Schmid-Hempel P., Butlin R., Martin S.J., Boots M. (2016). Deformed wing virus is a recent global epidemic in honeybees driven by Varroa mites. Science 351(6273): 594-597. doi.org
2. de Miranda J.R., Genersch E. (2010). Deformed wing virus. Journal of Invertebrate Pathology 103: S48-S61.
3. Martin S.J., Highfield A.C., Brettell L., Villalobos E.M., Budge G.E., Powell M., Nikaido S., Schroeder D.C. (2012). Global honey bee viral landscape altered by a parasitic mite. Science 336(6086): 1304-1306. doi.org
4. Paxton R.J., Schäfer M.O., Nazzi F., Zanni V., Annoscia D., Marroni F., Bigot D., Laws-Quinn E.R., Panziera D., Jenkins C., Shafiey H. (2022). Epidemiology of a major honey bee pathogen, deformed wing virus: potential worldwide replacement of genotype A by genotype B. International Journal for Parasitology: Parasites and Wildlife 18: 157-171. doi.org
5. Yue C., Schröder M., Gisder S., Genersch E. (2007). Vertical-transmission routes for deformed wing virus of honeybees (Apis mellifera). Journal of General Virology 88(8): 2329-2336. doi.org
6. de Miranda J.R., Fries I. (2008). Venereal and vertical transmission of deformed wing virus in honeybees (Apis mellifera L.). Journal of Invertebrate Pathology 98(2): 184-189. doi.org
7. Iqbal J., Mueller U. (2007). Virus infection causes specific learning deficits in honeybee foragers. Proceedings of the Royal Society B 274(1617): 1517-1521. doi.org
8. Benaets K., Van Geystelen A., Cardoen D., De Smet L., de Graaf D.C., Schoofs L., Larmuseau M.H.D., Brettell L.E., Martin S.J., Wenseleers T. (2017). Covert deformed wing virus infections have long-term deleterious effects on honeybee foraging and survival. Proceedings of the Royal Society B 284(1848): 20162149. doi.org
9. Fürst M.A., McMahon D.P., Osborne J.L., Paxton R.J., Brown M.J.F. (2014). Disease associations between honeybees and bumblebees as a threat to wild pollinators. Nature 506(7488): 364-366. doi.org
10. Mordecai G.J., Brettell L.E., Martin S.J., Dixon D., Jones I.M., Schroeder D.C. (2016). Superinfection exclusion and the long-term survival of honey bees in Varroa-infested colonies. The ISME Journal 10(5): 1182-1191. doi.org
11. Desai S.D., Eu Y.-J., Whyard S., Currie R.W. (2012). Reduction in deformed wing virus infection in larval and adult honey bees (Apis mellifera L.) by double-stranded RNA ingestion. Insect Molecular Biology 21(4). doi.org
12. Ramsey S.D. et al. (2019). Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph. PNAS 116(5): 1792-1801. doi.org
13. USDA APHIS, Veterinary Services (2023). Deformed Wing Virus (DWV). Case definition, monitored disease. aphis.usda.gov
14. USGS Bee Inventory and Monitoring Lab. Varroa destructor, photograph (public domain). usgs.gov

Updated : October 8, 2026
Written by : Apisanitas editorial team
Reviewed by : Review in progress