Purpose of review
In the past 2 years, at least three distinct human coronaviruses have been discovered, including the etiological agent associated with severe acquired respiratory syndrome (SARS). These recently discovered viruses, with the exception of the SARS associated coronavirus (SARS-CoV), are likely to be common respiratory viruses and may be responsible for a substantial proportion of respiratory tract disease.
The SARS-CoV first appeared in 2002 and spread rapidly around the globe. Although the worldwide spread of SARS-CoV may have been halted, the emergence of this new virus demonstrates the potential threat represented by species-to-species transmission of coronaviruses. NL63, initially isolated from a young child with lower respiratory tract disease, represents a group of newly described group I coronaviruses that have been identified worldwide, which are associated with both upper and lower respiratory tract disease, particularly in young children. The distribution of HKU1, a newly identified group II coronavirus, is not yet established. NL63 and HKU1 are related to the common human coronaviruses 229E and OC43, respectively.
The discovery of at least three new human coronaviruses represents significant advances in the investigation of human respiratory tract disease. Further studies are required to fully define the impact of these new pathogens.