92 Mumps
Mumps (infectious parotitis; epidemic parotitis) is a common, acute, viral infectious disease, principally of children, with worldwide distribution. It is frequently clinically characterized by fever and painful enlargement of one or more salivary glands.
Inapparent infection is common and occurs in about one- third of infections. Sometimes postpubertal males with mumps may develop painful swelling of the testicles, usually only on one side, with sterility an extremely rare complication. Mumps is a vaccine- preventable disease, but the vaccine is not yet widely used on a global basis.Etiology and Epidemiology
Mumps is caused by the mumps virus, a member of the genus Paramyxovirus of the family Paramyxo- viridae. Mumps virus has an irregular spherical shape averaging about 200 nanometers in diameter and contains a single-stranded RNA genome.
Mumps is a contagious disease, only slightly less contagious than rubella and measles, transmitted from infected persons to susceptible individuals by droplet spread and by direct contact with saliva. Mumps virus has also been shown to be transmitted across the placenta to the fetus. There is no natural reservoir for mumps other than human beings, which means that a continuous chain of susceptible contacts is necessary to sustain transmission. Although the period of communicability may be from 6 days before salivary gland symptoms to 9 days afterwards, the period of greatest infectivity is about 48 hours before salivary gland involvement. There is no carrier state. Mumps has an incubation period from time of exposure to onset of salivary gland swelling of about 18 days with a range of 2 to 3 weeks.
In populated areas with no or low vaccination coverage, mumps is primarily an endemic disease of children, with epidemics occurring in closely associated groups such as schools. Its peak incidence is found in the age group 6 to 10 years, and mumps is rare before 2 years of age.
Outbreaks may occur at intervals ranging from 2 to 7 years. There is a concentration of cases in the cooler seasons in temperate climates, and there is no apparent seasonality in tropical areas. In more remote isolated populations, mumps is not endemic, and disease depends upon introduction of the virus from the outside, at which time an epidemic may occur, affecting all age groups born since the previous epidemic. There is no evidence for a sex or racial difference in incidence of mumps, although clinically apparent mumps may be more common in males than in females.Distribution and Incidence
Serologic surveys as well as recorded outbreaks have demonstrated the existence of mumps throughout the world. Mumps is not a reportable disease in most countries, is underreported even in countries where it is a notifiable disease, and may be clinically inapparent in 30 to 40 percent of infections. In populated areas where mumps is both endemic and epidemic, over 80 percent of the adult population will show serologic evidence of prior infection. In remote or island populations where mumps is not endemic, a significant proportion of the population can be susceptible which may lead to large outbreaks when the mumps virus is introduced from the outside.
In some countries, such as the United States, where mumps is a reportable disease and mumps vaccine has been extensively used (often in combination with measles and rubella vaccine), there have been impressive declines in reported cases of mumps.
Immunology
Infants usually have a passive immunity to mumps because of maternal antibodies acquired transpla- centally from their immune mothers. This passive immunity protects the infant from mumps infection for about 6 months, depending on the amount of maternal antibody acquired.
Mumps infection in both clinically apparent and inapparent cases induces a lifelong immunity. Because a significant percentage of mumps infections are clinically inapparent, persons may develop immunity without recognizing they have been infected.
Several serologic tests for confirming infection or immunity have been developed, and it is also possible to isolate the virus from patients during the acute phase of the disease. Skin tests for immunity are not considered reliable.A single dose of live attenuated mumps virus vaccine confers long-term, probably lifelong, immunity in over 90 percent of susceptible individuals.
Clinical Manifestations and Pathology
The prodromal phase of mumps disease may be absent or include symptoms of low-grade fever, loss of appetite, malaise, and headache. Salivary gland swelling will often follow the prodromal period within a day, although it sometimes will not begin for a week or more. The salivary gland swelling progresses to maximum size in 1 to 3 days. The gland is painful and tender to the touch. Typically both the parotid salivary glands are affected, usually with one gland enlarging a few days after the other; hence the name “infectious or epidemic parotitis.” One-sided parotid gland involvement occurs in approximately one-fourth of patients who have salivary gland involvement. The fever may last for a variable period (from 1 to 6 days), and the parotid gland enlargement may be present for 6 to 10 days. It should be emphasized that approximately one- third of mumps cases may go unrecognized or be completely asymptomatic.
A common manifestation of mumps in approximately 20 to 30 percent of postpubertal males is painful testicular swelling (orchitis), usually onesided. Sterility is an extremely rare outcome of testicular involvement on both sides, which occurs in only approximately 2 percent of cases. The next most common manifestation of mumps is central nervous system involvement in the form of a usually benign meningitis, which may occur in about 10 percent of all infections. Uncommon manifestations of mumps include involvement and sometimes painful swelling of other glands such as the ovaries, breasts, thyroid, and pancreas. Mumps-associated complications are rare and may include encephalitis, neuritis, arthritis, nephritis, hepatitis, pericarditis, and hematologic complications.
Deafness, usually one-sided and often permanent, is reported to occur once per 20,000 cases of mumps. Although increased fetal mortality has been reported in women who contracted mumps during the first trimester, there is no evidence that mumps in pregnancy increases the risk of fetal malformations.History and Geography
In the fifth century B.C., Hippocrates is believed to have first recognized mumps as a distinct clinical entity in his work Epidemics I. He described an outbreak of an illness on the island of Thasus, noting that “swelling appeared about the ears, in many on either side, and in the greatest number on both sides... in some instances earlier, and in others later, inflammations with pain seized sometimes one of the testicles, and sometimes both.” Greek and Roman medical writers of antiquity as well as medieval practitioners at various times recorded cases of mumps-like illnesses, but there was relatively little study of the disease. Outbreaks of mumps in Paris in the sixteenth century were recorded by Guillaume de Baillou. In 1755 Richard Russell described mumps and expressed his opinion that the disease was communicable.
Mumps is called Ziegenpeter or Bauerwetzel in German and oreillons in French. The origin of the term “mumps” is unclear although it may come from the English noun mump, meaning a “lump,” or the English verb mump, meaning “to be sulky,” or even perhaps from the pattern of mumbling speech in individuals with significant salivary gland swelling.
In 1790, Robert Hamilton presented a very full description of mumps to the Royal Society of Edinburgh. He emphasized that orchitis was a manifestation of mumps and suggested that some mumps patients had symptoms of central nervous system involvement. In the beginning of the eighteenth century, interest in the study of epidemics helped to establish the communicability and wide geographic distribution of the disease.
August Hirsch collected references to some 150 epidemics occurring between 1714 and 1859 in temperate latitudes in both hemispheres as well as in cold, subtropical, and equatorial regions.
He specifically mentioned accounts of outbreaks that had occurred in diverse countries and places: “Iceland, the Faroe Islands, Lapland, Alaska, Egypt, Arabia, India, Malay Archipelago, Polynesia, the West Coast of Africa, Mexico, the West Indies, Peru, Italy, Sweden, Prussian Saxony, Schleswig and Holstein, the departments of Dusseldorf and Treves, the Cologne department, Martinique, Canton Zurich, Denmark, Lower Bavaria, Central Franconia, the quondam Duchy of Nassau, New York, Halle, Moscow, Bombay, and Berlin.” He also stated that during the American Civil War, 11,216 cases among Confederate troops were reported during the first year of the war and 13,429 cases during the second year. He concluded that mumps “occurs in widest diffusion over the globe, no part of the world being exempt from this strange malady.”Data have also demonstrated the occurrence of epidemic mumps in the closely associated populations of prisons, orphanages, boarding schools, garrisons, and ships. Indeed, Haven Emerson noted that mumps was the most important disease in terms of days lost from active duty in the American Expeditionary Force in France during World War I; and Surgeon General T. Parran of the U.S. Public Health Service stated in 1940 that mumps was one of the most disabling of the acute infections among armed forces recruits, exceeded only by the venereal diseases.
Despite earlier animal experiments suggesting that the fluid of the salivary glands was infective, C. D. Johnson and E. W. Goodpasture were not able to prove conclusively the viral etiology of mumps until 1934. They demonstrated that mumps was caused by a Altrable virus in saliva by transmitting mumps from patients to rhesus monkeys. In 1945 K. Habel successfully cultivated mumps virus in chick embryos. In 1948 G. Henle and associates experimentally confirmed the significant percentage of clinically inapparent infections by deliberately exposing 15 susceptible subjects to mumps, then following their clinical condition, isolating the virus, and performing serologic studies.
In 1951, an experimental killed-virus vaccine was used in humans. A live mumps virus vaccine has been used in the former U.S.S.R. since the early 1960s. In 1966 E. B. Buynak and M. R. Hilleman reported on the development of a live attenuated mumps virus vaccine, and they, R. E. Weibel, and others conducted a successful trial of the vaccine, which led to its licensure in 1967 in the United States.The worldwide geographic distribution of mumps is well documented, even in Hirsch’s collection of some 150 epidemics noted earlier. In populous countries without any sustained, large-scale immunization programs, mumps is widespread. In island or remote communities, large numbers of susceptible persons may exist. In countries with sustained, large-scale immunization programs, the impact of control efforts has been documented through decreasing numbers of cases of reported mumps.
Robert J. Kim-Farley
This chapter was written in the author’s private capacity. No official support or endorsement by the Centers for Disease Control is intended or should be inferred.
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