Species: Human astrovirus
is still a major cause of mortality worldwide, and the highest incidence of
diarrhea-related death occurs in developing nations . Astroviruses are one of
several viruses (including caliciviruses and rotaviruses) which can cause gastroenteritis.
Astroviruses were first observed in the feces of children in 1975 through electron
microscopy, and they are UBIQUITOUS among young
children. They are the second most common cause, after rotavirus, of viral diarrhea
in Thailand and Guatemala.
Basic properties of human astroviruses:
Initially appears to resemble picornavirus, but when viewed from a certain
angle, viral particles viewed by electron microscopy reveal a smooth or slightly
indented outer electron-dense shell with a negatively
staining 5 or 6 pointed star-like inner core.
- * Naked
virions are spherical and 28-30 nm in diameter.
- * Viral genome
consists of a single, linear RNA 7.2-7.9 kb molecule
that is single-stranded, positive
sense, and is polyadenylated at the 3' end.
- * Replication
occurs in cell cytoplasm. ·
- * Two
or three different proteins comprise the icosahedral capsid.
- * Mature virions
are often observed in crystalline arrays in the cell cytoplasm.
- * Virions are
hardy, for they are relatively resistant to heat and acidity.