Human noroviruses are a major cause of gastroenteritis outbreaks worldwide. They cause approximately 200,000 deaths each year in developing countries. However, no effective vaccine or antiviral agent for noroviruses yet exists because cell culture methods to produce noroviruses are very limited and there is a lack of the viral structural knowledge about the virus.
Click here for original story, Norovirus has two alternative capsid structures which change before infection
Source: Phys.org