Transmission of astroviruses occurs through the fecal-oral route.  See above.

Outbreaks commonly occur in nosocomial (hospital), day-care center, and familial settings.  Transmission via contaminated water and food can occur and lead to outbreaks as well.

Astroviruses cause clinical infections primarily in young children.  Adults are frequently seropositive and resistant to infection.  However, adult populations that are exposed to high levels of astroviruses can come down with astrovirus gastroenteritis.  These populations are frequently in constant and high exposure to the virus by contact with infected children (teachers, parents, medical caregivers).

Infections occur year round, however they also show a seasonal winter peak, similar to Rotavirus.

The elderly and the immunosuppressed can also be clinically infected with astrovirus.  These groups are at risk to hospital outbreaks of astrovirus gastroenteritis.

A recent study (by Maldonado et al, in 1988) found astroviruses to be present in 61% of Mayan infants and to be associated with 26% of all reported episodes of diarrhea.  In this study, astrovirus was the most common enteric pathogen, ahead of even Rotavirus.  In most studies, astrovirus is found to be the 2nd leading cause of infant diarrhea, behind Rotavirus.

Seroprevalence.  A UK study found that 77% of young adults were seropositive for astrovirus.  72% of the astrovirus encountered was serotype 1.  Strain 2-5 each accounted for 6-8%.  A additional study in Oxford between 1976 and 1992 found that serotype 1 accounted for 62% of the encountered astrovirus.

A recent  population based cohort study from Egypt indicated that in children under 3, the overall incidence of diarrhea caused by astrovirus was the same as that caused by rotavirus. 

A few other tidbits:  In the UK, 93% of surfers had antibodies to human astrovirus serotype 4 (vs 22% in age matched controls).  This illustrates the fact that transmission through contaminated water can occur.  In Japan, astrovirus was found in naturally growing oysters (in 15 of 112 samples).  And in fact, large food-born outbreaks affected thousands have occurred in Japan.

Treatment of infants is usually not necessary as astrovirus gastroenteritis is usually mild and self-limiting.  If dehydration symptoms occur, they can be treated with oral rehydration therapy (ORT).

Prevention of transmission and infection of astrovirus is accomplished by proper sanitation and hygiene.  This is especially important in hospitals and day-care centers where outbreaks among children can occur.  Astroviruses are rather resistant to alcohol disinfection but methanol is effective.

Proper hygiene and sanitation must be enacted at all times, not just when a known astrovirus infection is present.  This is because the virus is shed in the feces a day or two before and a day or two after the observable clinical symptoms.

Foods such as shellfish (especially oysters) have been implicated in harboring astroviruses and so should be selected, handled, and cleaned with care.

Currently no vaccine against astrovirus exists.