Historical Notes

   Astroviruses were first described in 1975 when they were observed in the feces of young children who
were either hospitalized with diarrhea or who were involved in outbreaks of gastroenteritis in newborn
nurseries. The term astrovirus was coined by Madeley and Cosgrove in 1975 to describe the structure of
the virus when viewed under an electron microscope: a small, round virus with a distinctive five- or
six-pointed starlike appearance (astron, meaning "star " in Greek).  Ironically, the first astroviruses
described in the literature did not display the characteristic astrovirus surface features; Appleton and
Higgins had reported an outbreak of mild diarrhea and vomiting among infants in a maternity ward a few
months earlier.  They found a virus in feces samples from these infants that had been shed in large
numbers and that were small, round, 29 to 30 nm in diameter, and without defining features.  By electron
microscopy, they could tell that these viruses differed from the previously identified Norwalk virus and
rotavirus because of their different size and morphology, but they could not be identified as any other
virus.  Years later, specific immunological reagents became available, and they were identified as
    Subsequently, viral particles that were of similar size and had characteristic starlike surface features
were associated with gastroenteritis in a wide variety of young mammals and birds including lambs,
calves, deer, piglets, kittens, mice, puppies, and turkey poults.  In addition, astroviruses were shown to
case a rapidly fatal hepatitis in ducklings.  Astrovirus, then, appears to cause infection in a
species-specific manner.
    In 1981, Lee and Kurtz reported the isolation of human astrovirus in human embryonic kidney (HEK)
cells, followed by serial passage of these viruses in a continuous line of rhesus monkey kidney epithelial
cells in the presence of trypsin.  The fact that these astroviruses could be propagated in cell culture clearly
distinguished them from Norwalk virus and other human caliciviruses that remain unable to grow in
culture.  This achievement also led to the recognition of five serotypes of human astrovirus in 1984, and a
development of an enzyme immunoassay in the late 1980s.  More recently, it has greatly facilitated the
cloning and sequencing of the astrovirus genome.