Acute Bee Paralysis Virus
There are three viruses Acute Bee Paralysis Virus (ABPV), Kashmire Virus (KV) and Israeli Acute Paralysis Virus (IAPV) that are very similar and, although they have some genetic differences, are considered together as a complex. Like Black Queen Cell Virus, the complex in the family Dicistroviridae, they are all associated with varroa infestation. For this reason control of varroa is the number one way to reduce these viruses.

ABPV was discovered in 1963

ABPV at first appearance is easily confused with Chronic Bee Paralysis Virus (CBPV)type 1. Dead or dying bees are found at the hive entrance. It is most common seen overtly in the apiary in summer / autumn.

The two main differences are that firstly it is of very sudden onset. Indeed it may be part of what is called colony collapse disorder (CCD). The second is that, unlike CBPV, ABPV is spread by the varroa mite.

The only way to know for sure is to perform polymerase chain reaction (PCR) on DNA of a dead bee's body.

The virus is commonly seen to exist in a colony as a covert low titre infection. When it becomes a clinical disease it is spread horizontally in crowded hives through the cytoplasm of broken cuticle hairs. It is spread vertically through feeding of larvae.

Scientific Beekeeping
Scientific Beekeeping
PCR sounds a bit like magic to anyone over 45. If you dont understand it ask any 17 year old studying biology. In this link the first 40 pages or so such get you up to speed..
This paper describes Acute Bee Virus Complex in some detail: The Acute bee paralysis virus, Kashmir bee virus, Israeli acute paralysis virus complex.