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The family Paramyxoviridae is a large one with several genera. The genus Morbillivirus contains canine distemper virus, rinderpest virus, peste des petits ruminants virus, equine morbillivirus and the human measles virus. A morbillivirus epizootic amongst pinnipeds killed nearly 20,000 seals in north-west Europe in 1987-88. The genus Paramyxovirus includes Newcastle disease virus, four serotypes of parainfluenza viruses (including Sendai virus which affects swine), several serotypes of avian paramyxoviruses, and human mumps virus. The genus Pneumovirus includes the respiratory syncytial viruses (RSV) of humans and cattle and the pneumonia virus of mice. It is to be expected that more pathogenic viruses will be found in this group.
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From September ‘98 to March ’99 a new paramyxovirus appeared in Malaysia. It was given the name Nipah virus and is related to Hendra virus which in 1994 caused fatal infections in horses and people in Australia.
[The new genus Henipavirus was proposed to classify these new viruses.] Nipah virus causes an encephalitis that clinically is indistinguishable from Japanese Encephalitis: fever, headache, vomiting, reduced consciousness, meningism, myoclonus, convulsions, areflexia and hypotonia, tachycardia, abnormal pupils, nystagmus. There is often a considerable effect on the brain stem, often resulting in an abnormal oculovestibular reflex (abnormal "doll’s eye reflex"). Sometimes there is a non-productive cough. In man, the mortality rate is high. During the first epidemic more adults than children were affected, mainly those who were working as pig-farmers. Pigs can be infected and develop a cough. In animals, infection often results in death, unlike with Japanese Encephalitis. Flying foxes (large bats, including Pteropus hypomelanus) are thought to be the reservoir. The virus has been isolated from their urine and saliva.*
Another new paramyxovirus has been named Menangle virus, after its discovery in 1998 in sows on a large swine farm near Menangle, New South Wales. In the animals, it provoked abortion. Two men who had worked with the pigs had been sick for 2 weeks with severe flulike symptoms. Antibodies in their blood matched those taken from infected sows. Nearby gray-headed fruit bats tested positive for the virus. As far as is known at present, neither Nipah virus nor Menangle virus are arboviruses.
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Early 2004, a new pathogenic Nipah-related virus appeared in Bangladesh. At the time of writing, intensive research is going on in order to find out more about this emerging pathogen.
