Astroviruses, belonging to the family Astroviridae, were first identified in 1975 using electron microscopy during an outbreak of diarrhea in humans. Since then, astroviruses have been found in a wide range of hosts. In mammals, they are classified under the genus Mamastrovirus, while those infecting birds—such as ducks, chickens, and turkeys—fall under the genus Avastrovirus.

These viruses are non-enveloped, icosahedral particles measuring 28–35 nm in diameter. Under electron microscopy, they display a distinctive star-like appearance with five- or six-pointed projections. Astroviruses have a non-segmented, single-stranded, positive-sense RNA genome enclosed within their capsid. Alongside Picornaviridae and Caliciviridae, Astroviridae is one of the three major families of non-enveloped RNA viruses with similar genomic structures.

In humans, especially young children, astroviruses are a significant cause of gastroenteritis globally. In animals, while they primarily infect the gastrointestinal tract, astroviruses have also been associated with more severe conditions such as encephalitis (in humans and cattle), hepatitis (in birds), and nephritis (also in birds).