Wed Apr 19, 5:55 PM ET
WASHINGTON (Reuters) - The number of mumps cases has risen to 1,100 in eight Midwestern states and prompted the federal government to distribute vaccines from its stockpile to stop the outbreak's spread, health officials said on Wednesday.
The outbreak is the largest mumps epidemic in the United States in more than 20 years, the U.S. Centers for Disease Control and Prevention said.
Most are in Iowa, where 815 cases have been recorded, the CDC said.
An additional 350 mumps cases have been reported in Minnesota, Kansas, Illinois, Nebraska, Wisconsin, Missouri and Oklahoma, officials said. Investigators are reviewing possible cases in seven other states that were not named.
Mumps usually is not serious and rarely kills. None of the cases in the recent outbreak have been fatal.
Once a common childhood illness, mumps was virtually eradicated with widespread use of the measles, mumps and rubella (MMR) vaccine.
But the vaccine is effective in only about 90 percent of people, which could partly explain the recent outbreak, CDC Director Julie Gerberding said.
"Although this is a very good vaccine, it's not perfect," Gerberding said at a news conference.
Many college-age students may have received just one of the two recommended doses when they were young, and therefore may not have the same level of immunity as others, she said.
Federal officials urged students, people who work in school or university settings and health-care workers who did not get both doses to get a second dose.
The CDC is sending 25,000 doses of MMR vaccine to Iowa for that purpose, Gerberding said. Drug maker Merck & Co. Inc. has donated an additional 25,000 doses for health officials to use as they see fit.
Investigators do not yet know how many of the people infected with mumps were vaccinated. So far, "we have absolutely no information to suggest there's a problem with the vaccine," Gerberding said.
Mumps is a viral infection of the salivary glands. It causes unpleasant illness including fever, headache and swelling of the glands around the jaw.
Up to 10 percent of patients may develop encephalitis. Other serious complications that sometimes occur include meningitis, inflammation of the testicles, ovaries or pancreas, or permanent deafness. There is no approved treatment.
The mumps virus is transmitted by coughing and sneezing. Experts say it is about as infectious as influenza. People can transmit mumps to others for three days before they have any symptoms.
In the United States, an average of 265 mumps cases have been reported each year since 2001. Mumps vaccinations started in 1967.
CDC HEALTH ADVISORY
Distributed via Health Alert Network
Friday, April 14, 2006, 20:34 EDT (08:34 PM EDT)
Multi-state Mumps Outbreak
The state of Iowa has been experiencing a large outbreak of mumps that began in December 2005 (1). As of April 12, 2006, 605 suspect, probable and confirmed cases have been reported to the Iowa Department of Public Health (IDPH) (IDPH, unpublished data). The majority of cases are occurring among persons 18-25 years of age, many of whom are vaccinated. Additional cases of mumps, possibly linked to the Iowa outbreak, are also under investigation in eight neighboring states, including Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, and Wisconsin (CDC unpublished data, April 14, 2006).
In addition, the Iowa Department of Public Health has identified two persons diagnosed with mumps who were potentially infectious during travel on nine different commercial flights involving two airlines between March 26, 2006 and April 2, 2006. The origin and arrival cities for these flights include Cedar Rapids and Waterloo, IA; Dallas, TX; Detroit, MI; Lafayette, AR; Minneapolis, MN; St. Louis, MO; Tucson, AZ; and Washington, D.C. (2).
The source of the current US outbreak is unknown. However the mumps strain has been identified as genotype G, the same genotype circulating in the United Kingdom (UK). The outbreak in the UK has been ongoing from 2004 to 2006 and has involved > 70,000 cases. Most UK cases have occurred among unvaccinated young adults (3). The G genotype is not an unusual or rare genotype and, like the rest of known genotypes of mumps, it has been circulating globally for decades or longer.
Mumps clinical manifestations and transmission
Mumps is an acute viral infection characterized by a non-specific prodrome including myalgia, anorexia, malaise, headache and fever, followed by acute onset of unilateral or bilateral tender swelling of parotid or other salivary glands (4). In unvaccinated populations, an estimated 30-70% of mumps infections are associated with typical acute parotitis (4, 5). However, as many as 20% of infections are asymptomatic and nearly 50% are associated with non-specific or primarily respiratory symptoms, with or without parotitis (4).
Complications of mumps infection can include deafness, orchitis, oophoritis, or mastitis (inflammation of the testicles, ovaries, or breasts respectively), pancreatitis, meningitis/encephalitis, and spontaneous abortion. With the exception of deafness, these complications are more common among adults than children (4).
Transmission of mumps virus occurs by direct contact with respiratory droplets, saliva or contact with contaminated fomites. The incubation period is generally 16-18 days (range 12-25 days) from exposure to onset of symptoms (4, 6). Mumps virus has been isolated from saliva from between two and seven days before symptom onset until nine days after onset of symptoms (4, 6).
The principal strategy to prevent mumps is to achieve and maintain high immunization levels. The Advisory Committee on Immunization Practices (ACIP) recommends that all preschool aged children 12 months of age and older receive one dose of measles-mumps-rubella vaccine (MMR) and all school-aged children receive two doses of MMR, and to ensure that all adults have evidence of immunity against mumps (5). As noted below, two doses of mumps vaccine are more effective than a single dose. Consequently, during outbreaks and for at-risk populations, ensuring high vaccination coverage with two doses is encouraged. For example, health care workers may be at increased risk of acquiring mumps and transmitting to patients and thus should receive two doses of MMR vaccine or provide proof of immunity. Since vaccination is the cornerstone of mumps prevention, public and private health entities concerned about spread of mumps in a population can review the vaccination status of populations of interest and work to address gaps in vaccination.
Mumps Vaccine Effectiveness
Data from outbreak investigations have shown that the effectiveness of MMR against mumps is approximately 80% after one dose and limited data suggest effectiveness of approximately 90% after two doses. Available evidence suggests that mumps vaccination should provide immunity against the genotype G virus responsible for the current US outbreak. A study of a 2005 New York outbreak that began with imported disease from the UK (7), demonstrated vaccine effectiveness in the expected range for both one and two doses (New York, unpublished data). However, since the vaccine is not 100% effective, some cases can occur in vaccinated persons. When a highly-vaccinated population is exposed to disease, most cases of disease would be expected to be among vaccinated persons. Mumps vaccine has not been shown to be effective in post-exposure prophylaxis and an interval of 2-4 weeks after vaccination may be required for the vaccine’s full immunogenicity to be achieved. For these reasons, and because of the mumps’ incubation period of 12-25 days, during an outbreak, newly-vaccinated persons may develop mumps disease as long as a month after vaccination (4, 5).
Control of mumps outbreaks
The main strategies for controlling a mumps outbreak are to define the at-risk population and transmission setting, identify and isolate suspected cases, and to rapidly identify and vaccinate susceptible persons or, if a contraindication to MMR vaccine exists, to exclude susceptible persons from the setting to prevent exposure and transmission. Specific strategies are listed below.
1. Offer MMR vaccine to persons without evidence of immunity. Evidence of immunity includes physician diagnosis or laboratory evidence of mumps infection, birth before 1957 or one dose of MMR vaccine. For pre-school aged children, the first MMR dose should be administered as close to age 12 months as possible. Although birth before 1957 is usually considered proof of immunity, during an outbreak, vaccination can be considered for this age group if the epidemiology of the outbreak suggests that they are at increased risk of disease. Since two doses of MMR vaccine is more effective than one dose for preventing mumps, a second dose of MMR vaccine is recommended for the following groups: health care workers, school-aged children, students at post-high school educational institutions and other age groups considered at high risk of exposure (5, 8).
2. Surveillance for mumps should be enhanced in all affected areas for persons with parotitis or other salivary gland inflammation. Enhanced surveillance should continue for 50 days (two times the maximum incubation period) after the date of illness onset in the last identified case. CSTE approved case definitions and case classifications for mumps are available (5).
3. Persons with suspected mumps should be tested and reported immediately to local public health officials. Information on collection and testing of clinical specimens for mumps will be available by Monday April 17, 2006 at http://www.cdc.gov/nip/diseases/mumps/mumps-lab.htm. Testing is essential as not all cases of parotitis are mumps, although mumps is the only known cause of epidemic parotitis.
4. Persons suspected of having mumps should be isolated for nine days after symptom onset (5, 6). In health care settings, the use of respiratory precautions is recommended (5).
5. Exclusion of persons without evidence of immunity to mumps from institutions such as schools and colleges affected by a mumps outbreak (and other, unaffected institutions judged by local public health authorities to be at risk for transmission of disease) should be considered. Once vaccinated, students can be readmitted to school. The period of exclusion for those that remain unvaccinated should be for at least 25 days after the onset of parotitis in the last person with mumps in the affected institution (5, 6).
Additional information on mumps and the prevention and control of mumps outbreaks, including vaccination, can be found at the following website:
Please note: An erratum has been published for this article. To view the erratum, please click here.
On April 11, this report was posted as an MMWR Dispatch on the MMWR website (http://www.cdc.gov/mmwr).
The state of Iowa has been experiencing a large mumps outbreak that began in December 2005 (1). As of April 10, 2006, a total of 515 possible mumps cases have been reported to the Iowa Department of Public Health (IDPH) during 2006 (2). This outbreak has spread across Iowa, and mumps activity, possibly linked to the Iowa outbreak, is under investigation in six neighboring states, including Illinois (n = four), Kansas (n = 33), Minnesota (n = one), Missouri (n = four), Nebraska (n = 43), and Wisconsin (n = four) (CDC, unpublished data, April 10, 2006). The reasons for this outbreak are under investigation.
Mumps is an acute viral infection characterized by a nonspecific prodrome, including myalgia, anorexia, malaise, headache, and fever, followed by acute onset of unilateral or bilateral tender swelling of parotid or other salivary glands (2). An estimated 60%--70% of mumps infections produce typical acute parotitis (3). Approximately 20% of infections are asymptomatic, and nearly 50% are associated with nonspecific or primarily respiratory symptoms. Complications include orchitis, oophoritis, or mastitis (inflammation of the testicles, ovaries, or breasts, respectively), meningitis/encephalitis, spontaneous abortion, and deafness. Transmission occurs by direct contact with respiratory droplets or saliva. The incubation period is 14--18 days (range: 14--25 days) from exposure to onset of symptoms. The infectious period is from 3 days before symptom onset until 9 days after onset of symptoms.
IDPH has identified two persons who had mumps diagnosed and were potentially infectious during travel on nine different commercial flights involving two airlines during March 26--April 2, 2006. The commercial airline flights identified with a potentially infectious traveler are listed below by date, carrier, and flight number:
Northwest Airline (NWA) flights:
March 26 NWA (Mesaba) #3025 from Waterloo, Iowa to Minneapolis, Minnesota
March 26 NWA #760 from Minneapolis, Minnesota, to Detroit, Michigan
March 27 NWA #0260 from Detroit, Michigan, to Washington, DC--Reagan National
March 29 NWA #1705 from Washington, DC--Reagan National to Minneapolis, Minnesota
March 29 NWA (Mesaba) #3026 from Minneapolis, Minnesota, to Waterloo, Iowa
American Airline (AA) flights:
April 2 AA #1216 from Tucson, Arizona, to Dallas, Texas (DFW)
April 2 AA #3617 from DFW to Lafayette, Arkansas (Northwest Arkansas Regional [NAR])
April 2 AA #5399 from NAR to St. Louis, Missouri
April 2 AA #5498 from St. Louis, Missouri, to Cedar Rapids, Iowa
Persons on these flights who have symptoms consistent with mumps within 21 days of travel should be evaluated for mumps by a health-care provider. Health-care providers should remain vigilant for mumps among persons with parotitis or other salivary gland inflammation. Cases of suspected mumps should be reported immediately to public health officials.
A multistate investigation has been initiated by CDC and the state health departments in affected states to notify potentially exposed passengers (i.e., those seated in close proximity to the index cases). This investigation is using a new software application, eManifest, developed by the CDC Division of Global Migration and Quarantine (DGMQ) to securely import, sort, and assign passenger-locating information to jurisdictions to facilitate timely identification of exposed persons. These data are securely transmitted to state and territorial health departments via the Epidemic Information Exchange (Epi-X) Forum (available at http://www.cdc.gov/mmwr/epix/epix.html) for notification of potentially exposed passengers.
Incidence of mumps in the United States began to decrease after vaccine introduction in 1967 and recommendations for routine vaccination of children in 1977. Since the 1990s, a further decrease in the reported incidence of mumps has occurred, which is thought to be attributable to the implementation of the second dose of measles, mumps, and rubella vaccine (3). The risk for transmission of respiratory infectious diseases during air travel might depend on several factors, including 1) immunity of passengers; 2) infectiousness of the organism; 3) degree of shedding of the pathogen by infected passengers; 4) hygienic practices of infectious passengers; 5) proximity of others to infectious passengers; 6) hygienic practices of the other passengers/crew; 7) flight duration; and 8) cabin environment of the aircraft (4). Transmission of other respiratory pathogens during air travel has been reported (5--9). Exposure and transmission of mumps during commercial air travel has not been described previously.