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Mumps Virus

by Adam Johnson


Mumps is a paramyxovirus that is closely related to the parainfluenza virus. Its symptoms were first described in the 5th century BC, and it was a very common childhood affliction until the last several decades. It was identified as a virus in 1934, and an effective vaccine was developed in 1967. Mumps is acquired by aerosol, necessitating close human interaction for spread. Human beings are the only known reservoir for mumps virus, and there is only one serotype.

Multiplication


The virus is primarily spherical shaped and roughly 200nm in size, surrounded by a host-cell derived membrane. Its genome is minus-sense single-stranded RNA 16-18 kb in length. It contains matrix protein inside the envelope, hemagglutinin and neuraminidase, fusion protein, nucleocapsid protein, and L and P proteins to form the RNA polymerase. The host-cell receptors on the outside are hemagglutinin and neuraminidase. The virus is allowed to enter the cell when the hemagglutinin/ neuraminidase glycoproteins fuse with the sialic acid on the surface of the host cell, and the capsid enters the cytoplasm. The infected cells express the fusion protein from the virus, and this links the host cells together to create syncitia.
The virus replicates in the cytoplasm and is released through budding.

Spread and Symptoms


Mumps is primarily a childhood disease, occurring most frequently between the ages of 5 to 9, although it was also known as a problem for soldiers during war because of the sanitary conditions and close proximity. For instance, in World War I only influenza and gonorrhea were more prevalent among the armies. It replicates inside the nose, throat, and regional lymph nodes. The virus incubates for about 14-18 days, and then a viremia occurs for about 3-5 days. During the viremia it can spread to the meninges, salivary glands, testes, ovaries and pancreas. Out of the infected population, 30 to 40% get swollen parotid salivary glands, with most of the rest being asymptomatic or having only respiratory problems. Around 60% of patients have asymptomatic meningitis, with up to 15% progressing to symptomatic. Encephalitis is also possible, occurring in around 5/100,000 cases. The encephalitis almost always results in some permanent hearing loss, and was historically the leading cause of hearing loss in children. Orchitis (testicular swelling) happens in up to 50% of post-pubertal males, with oophritis (ovarian swelling) happening in only 5% of women. Orchitis often results in testicular atrophy but very rarely in sterility. It has also been shown as a possible risk factor for testicular cancer. Mumps deaths are vary rare, with an average of about 1 per year in the United States.

Prevalence


Mumps is endemic in most tropical areas of the world, and is common everywhere else. In the USA it peaks in late winter to early spring. Worldwide infection rates are from 100 to 1,000 per 100,000. In the USA, 212,000 cases were reported in 1964, before the live attenuated vaccine was licensed. In 1983, after the vaccine was in use for about 15 years, the reported cases dropped to 3,000. There was a slight resurgence in 1986 and 87, and it was determined that a second dose given around a month after the first was necessary for complete and lasting immunity. In 2001 there were 231 reported cases.

Treatment


There is no treatment for mumps, although corticosteroids are given in extreme cases to reduce salivary gland swelling. The vaccine was created in 1967 and can be given by itself, with the measles vaccine, or with measles and rubella in the MMR vaccine, which has been proven to be from 95 to 99% effective. The mumps part of the vaccine has very few side effects, mainly a slight fever. Lately there has been controversy over whether or not the MMR vaccine is a cause of autism. A study examined the age of diagnosis of autism for children that had the MMR vaccine versus those who didn’t, and showed that there was no difference. The CDC and WHO both assert that there is no correlation.


"MMR and autism." World Health Organization. 1 Apr. 2003.
http://www.who.int/vaccines-diseases/safety/hottop/mmrstatement.shtml
"Mumps." Centers for Disease Control. 1 Apr. 2003.
http://www.cdc.gov/mumps/index.html
"Vaccines, Immunization, and Biologicals: Mumps Vaccine." World Health
Organization. 1 Apr. 2003. http://www.who.int/vaccines/en/mumps.shtml

 

© 2010, J.Graf. Site made by Adam Johnson, for comments please contact Joerg.Graf@uconn.edu