[Human coronaroviruses]

Coronaviruses are a large group of viruses and infect a lot of species of mammals and birds. Five coronaviruses currently infect humans: HCoVs 229E and OC43, identified in 1960's, SARS-CoV identified in March 2003 during the SARS epidemic, and the HCoVs NL63 and HKU1, identified in 2004 and 2005. The genome of the coronaviruses is a linear, nonsegmented, positive-sense single-stranded RNA molecule of approximately 30 kb. The evolution of these viruses occurs through some features: the flexibility of the genome including a high number of potentially non-essential genes, the demonstrated ability of the coronaviruses to establish persistent infections, the quasi-species structure of the viral population, the ability to undergo RNA mutations, deletions and recombinations at a high frequency. Two epidemiologic pictures of human coronavirus infections have to be distinguished: as suggested by a few epidemiologic studies, the classical coronaviruses, including HCoVs 229E, OC43, and NL63 are distributed worldwide and would circulate during seasonal outbreaks. In contrast, the SARS-CoV is responsible of the first new emerging infectious disease of this millennium, infecting more than 8,000 people and killing nearly 800 during a period of six months beginning at the end of 2002. Human coronaviruses may be also involved in enteric and neurologic diseases. The detection of coronaviruses is difficult and mainly based on molecular assays (RT-PCR). Despite research activities on the development of vaccines and antiviral agents, there is no established specific therapy to date.