Coronavirus is a genus of pleomorphic (displaying multiple forms) viruses which look like coronas or halos when they are viewed with a microscope. It is the single genus of the family Coronaviridae.
Members of Coronavirus cause:
Some research has also implicated coronaviruses in human neurologic disorders like multiple sclerosis, but the data is not definitive.
Coronaviruses are important pathogens in house cats; feline infectious peritonitis virus (FIPV) and feline enteric coronavirus (FECV) are essentially the same virus and can cause fairly serious disease in places like cat breeding facilities where cats are kept in close quarters. There is a vaccine for feline coronavirus, but there is no good treatment for a cat once it is sick, though some vets have used corticosteroid therapy with varying success. Most cats recover, however.
Part of the information in this writeup was gleaned from http://maxshouse.com/FIP%20Update.htm. The rest is based on the entry from the science dictionary at http://biotech.icmb.utexas.edu/