The astrovirus is an infection agent that causes gastroenteritis. It affects certain species of mammals and birds including humans, cows, sheep and chickens. It is named after the Greek word for "star" because of its shape. Like other viruses, it attacks cells in its host in order to replicate itself.
Astroviruses were first discovered in 1975 using electron microscopes after a diarrhea outbreak. The astrovirus formed part of a newly-discovered family of viruses called the astroviridae. There are two main types of astroviruses: mamastroviruses affect mammals and avastroviruses affect birds. These are further subdivided by the species they affect and their serotypes. A serotype is a small variation in the basic virus’ form, and there are seven known human serotypes of the astrovirus.
The virus looks like a five- or six-pointed star, hence the name, and is approximately 28 to 35 nm or nanometers in diameter. Its capsid, or protein shell, is icosahedral in shape and is non-enveloped. The virus’ genome is a single strand of ribonucleic acid (RNA).
Symptoms of the astrovirus are similar to those of gastroenteritis. Diarrhea, nausea, vomiting and fevers are common symptoms. Patients may also suffer from malaise and abdominal pain. Such symptoms last for around three to four days before naturally subsiding as the body produces antibodies.
There are a number of scientific techniques for identifying the astrovirus. These include electron microscopy, enzyme-immunoassays (ELISA) and immunofluorescense. All techniques are used to find virus particles, antigens and viral nucleic acids present in stool samples.
Astroviruses tend not to cause great problems for the patient. The body tends to produce antibodies within a few days to deal with the problem. It is more dangerous for individuals with weak immune systems. Scientists have not developed a vaccine or anti-viral treatment.
The best prevention method for the virus is simple hygiene. It typically enters patients through the mouth via the hands, food or water. Good sanitation, cleanliness and food preparation are essential for reducing the risk of an astrovirus outbreak.
Children under 10, especially under 2, are at most risk for developing gastroenteritis because of an astroviral infection. By the age of 5, most children have built up immunity to it, however, some adults and elderly people have been known to develop it. It is thought to cause a quarter of all gastroenteritis cases in children, and case numbers peak in the winters and rainy seasons. The most common astrovirus in humans is serotype one.