New Human Astroviruses

The first human astrovirus was discovered in 1975 by Madeley and Cosgrove through visualization of viral particles in stool using electron microscopy. Over the course of the next ∼20 years, an additional seven serotypes of human astroviruses were discovered. In the last decade, new technological advances in microarrays and sequencing strategies enabled more sophisticated methods for detecting viruses in clinical and environmental specimens. These methods led to the discovery of many novel viruses from a variety of virus families. They also brought about a dramatic realization that more astroviruses can be found in humans than previously recognized. In fact, the number of astroviruses associated with humans has nearly doubled within the last few years. Furthermore, the discovery of novel astroviruses in human specimens revealed that there is more diversity amongst them than was assumed based on the high level of similarity between human astroviruses 1 and 8. This chapter will describe the discovery and early characterization of the five novel astroviruses initially identified in human stool samples in 2008 and 2009.