Paramyxoviruses are an important class of viruses which are associated with respiratory ailments, and common childhood diseases such as measles and mumps. Paramyxoviruses are a significant cause of morbidity and mortality globally, especially in children and the elderly.
Paramyxoviruses encode negative-sense, single-stranded, monopartite RNA. They are enveloped and contain a helical nucleocapsid. They appear pleomorphic or spherical in electron micrographs.
-ssRNA must first be converted into +ssRNA (mRNA) by the RNA-dependent RNA polymerase (RDRP) incorporated in the virion. The mRNA can then be translated into proteins. Replicative enzymes (RDRP) synthesize a negative-strand copy of the +RNA. Structural proteins translated from the mRNA are then used to package progeny -RNA and RDRP into virions.
Incubation: Normally 8-14 days
Epidemiology: There is only one serotype of measles that causes the disease. Main route of transmission is via inhalation. Recently the prevalence of measles has decreased dramatically in developed nations, but measles is still a problem in third-world nations, especially in Africa and Central and South America.
Symptomatology and Outcome
Oral exanthem of Measles infection
Classic non-vesicular exanthem associated with measles
Another classical case of measles exanthem
Swollen parotid glands, a classic symptom of mumps
Incubation: 12-25 days, but normally 16-18 days
Man is the only known natural host. Mumps is prevalent worldwide, but incidence has significantly decreased in developed nations due to MMR vaccination. Mumps is known as a “childhood” disease because it normally affects children under 10 years of age. The virus is transmitted by respiratory secretions and by saliva via aerosol form and/or fomites.
Symptomatology and Outcome
Respiratory Syncytial Virus
Incubation: The incubation period of RSV is typically between 4 to 6 days.
Symptomatology and Outcome
MYSTERIOUS ENCEPHALITIS IN BANGLADESH
In mid-January of 2004, there were ten deaths from encephalitis in Bangladesh. The culprit was found to be Nipah or a Nipah-like virus, Hendravirus, which is a recently discovered paramyxovirus. Nipahvirus is thought to have caused an encephalitis outbreak in 1998/1999 in Malaysia, resulting in 300 confirmed infections with 35% mortality rate. The virus is thought to be a zoonosis from pigs.
ACUTE RESPIRATORY INFECTION OUTBREAK IN CAMBODIA
Beginning on June 5, 2005, many children developed acute respiratory infections in Cambodia. Amongst the viruses detected were RSV, human metapneumovirus, parainfluenza viruses 1-4, and influenza A and B. Many of the cases were noted to be co-infections of RSV and influenza B.
DISCOVERY OF THE MODE OF NIPAHVIRUS CELL INFECTION
Scientists at UCLA have discovered how Nipahvirus, a virus that causes encephalitis and death in up to 70% of its victims, infects its host cell. The viral particle binds to Ephrin B-2, a receptor crucial to nervous system development and the growth of blood vessels.
DIFFERENTIAL RESPONSE OF DENDRITIC CELLS TO hMPV and RSV
Scientists at the University of Texas have recognized that dendritic cells respond differently to hMPV and RSV infection. Monocyte-derived cells were susceptible to infection by both viruses, but only RSV was able to effectively induce infection and replication of the viral particle. RSV-infected monocyte derived cells were more severely affected in their ability to stimulate CD4+ T cell production than hMPV infected cells. This research will allow scientists to create more effective medications to combat the different effects of each virus.
hMPV INDUCES A PROFILE OF LUNG CYTOKINES DISTINCT FROM THAT OF RESPIRATORY SYNCYTIAL VIRUS
hMPV induces differential cytokine production from RSV. This finding may bring about new potential treatments and/or establish new methodologies in diagnosis and differentiating between other respiratory tract infections.
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