Astroviruses cause gastroenteritis, predominantly diarrhea, usually in children under five years old although it has been reported in adults. Studies show that more than 80% of children between 5 and 10 years old have antibodies to astroviruses, suggesting they have been exposed to it at some point. Occasional outbreaks in schools, nurseries and families have been reported. However, the number of infections may be under-estimated, since the illness is usually mild, and many cases go unreported. The illness is self-limiting, has a short duration and incidences peak in the winter.

Limited information is available on the environmental occurrence of human astroviruses. However, since infected individuals may excrete large numbers of viruses in their feces, they are present in sewage, and contraction of them from sewage-polluted waters can occur. Since viruses only replicate in living host cells no increase in numbers will occur in the environment.

Person to person spread by the fecal-oral route is thought to be the most common route of transmission. Recent work with sensitive assay techniques has shown the prevalence of this virus to be much higher than previously thought. It is endemic all over the world, second only to Rotavirus as a cause of childhood diarrhea.