Members of the Paramyxovirus family of viruses are negative-sense single-stranded RNA viruses responsible for a number of human diseases. The viruses that cause measles and mumps belong to this family, as do respiratory syncytial virus (RSV) which causes pneumonia and parainfluenza virus which causes pneumonia, bronchitis and croup, especially in children. Human metapneumovirus, initially described in about 2001, is also implicated in bronchitis, especially in children.
Paramyxoviruses are also responsible for a range of diseases in other animal species, for example canine distemper. Some paramyxoviruses such as the henipaviruses are zoonotic pathogens, occurring naturally in an animal host, but also able to infect humans.
As of March 2003, a group of doctors in Hong Kong claims to have identified the agent causing severe acute respiratory syndrome (SARS) as belonging to the paramyxoviridae family of viruses. Similar findings (electron microscopy showing viral particles whose structure was suggestive of paramyxoviruses) were reported in two cases of the disease by researchers at Frankfurt University. Canadian scientists have found human metapneumovirus in some secretions of SARS patients. However, CDC studies have suggested a previously unrecognized coronavirus may be the cause of SARS. Viruses are ubiquitous and it is not surprising that different viruses are isolated from various patients: further studies are needed to determine which virus is responsible for SARS.