ARCHIVED - Guidelines for the Prevention and Control of Mumps Outbreaks in Canada
6.1 Spread and Control
Mumps is generally spread by close face-to-face contact. Infection occurs through direct contact with saliva or respiratory droplets from the nose or throat, spread through coughing, sneezing, sharing drinks, or kissing, or from contact with any surface that has been contaminated with the mumps virus(8-11).
The incubation period for mumps ranges from 14 to 25 days(8-11). Once an individual is infected, mumps can be communicable from 7 days before to 5 days after the onset of parotitis (swelling of the parotid gland)(12). A recent review of the scientific evidence suggests that, while the mumps virus can be isolated from saliva or respiratory secretions ≥5 days after parotitis onset, the risk of transmission after 5 days is considered low, due to decreasing viral load(12). Approximately 20% to 30% of mumps infections can be asymptomatic, and these cases can also be infectious(8,11). High childhood immunization rates in Canada have resulted in a dramatic reduction in rates of mumps infection. Under-immunized and unimmunized children and young adults remain the groups at highest risk of infection. Immunity is generally lifelong and develops after either inapparent (asymptomatic) or clinical infections. Mumps immunization is further discussed in Section 7.
The public health response to increased mumps activity includes managing cases, contact identification and management; identifying social networks when individual follow-up is not feasible; and maintaining/enhancing surveillance for further cases and disease outcomes (e.g., hospitalizations, complications). Generally, a mumps outbreak is controlled by the following methods(13-15):
- defining the at-risk populations and transmission settings;
- preventing further transmission through isolation of cases and contact education/ awareness;
- protecting susceptible populations with immunization (where no contraindication to MMR vaccine exists); and
- good risk communication.
6.2 Case Management
There is no specific or prophylactic treatment for mumps; all confirmed and clinical cases of mumps should be offered supportive care. Cases should be encouraged to practise good hand hygiene, avoid sharing drinking glasses or utensils, and cover coughs and sneezes with a tissue or forearm.
Clinical cases should be advised to stay home from school or post-secondary educational institutions, child care facilities, workplaces, and other group settings for 5 days from symptom onset. Self-isolation will prevent exposure of susceptible individuals to the virus. CDC has revised their recommendation for self-isolation from 9 days to 5 days, citing new information about the period of communicability of mumps(12). Although the mumps virus has been isolated from respiratory secretions >5 days after parotitis onset, the risk of transmission 5 days after parotitis onset is low(12). During recent mumps outbreaks in Nova Scotia (2007), Iowa (2006), and the United Kingdom (2006), local public health authorities found that there were compliance issues with the 9-day self-isolation requests.
Cases in health care facilities should be managed with droplet precautions (in addition to routine practice) until 5 days after symptom onset.
6.3 Contact Management (Refer to Section 6.4.3 for management of contacts who are health care workers)
Contacts of mumps cases (as defined in Section 4.3) who are considered susceptible to mumps infection include the following:
- those born in Canada in 1970 or later who did not receive two doses of mumpscontaining vaccine (at least 4 weeks apart) after their first birthday;
- those who have not had laboratoryconfirmed mumps; and
- those who do not have documented immunity to mumps(16).
Immunization of mumps-susceptible contacts with MMR vaccine should be considered. However, immunization after exposure may not prevent infection. Passive immunization with immunoglobulin is not effective in preventing mumps. In addition, isolation of mumps-susceptible contacts is not required. On the basis of the epidemiology of the outbreak, susceptible groups should be targeted for immunization, especially those at greatest risk of exposure. Mumps immunization is further discussed in Section 7.0.
Public health capacity during the 2007 outbreak in the Maritimes was quickly overwhelmed by the resources required for individual contact tracing and management. At the start of an outbreak, individual contacts can be managed either directly by public health authorities or indirectly by asking cases to disseminate information to their contacts. Depending on the age groups and settings involved in the outbreak, alternative follow-up mechanisms may be considered to effectively reach large numbers of contacts and other at-risk groups. Examples of alternatives that were used are letters or cards to copy and distribute, the Internet or established e-mail distribution lists, public service announcements, press releases, and a toll-free telephone number.
The logistics of providing immunization to susceptible contacts and at-risk populations should be carefully considered. Some of the issues encountered in managing previous out-breaks included vaccine supply and acquisition costs, low uptake by the college/university-aged cohort, accurate determination of susceptible groups complicated by poor or non-existent immunization records, and vaccine administration and related costs.
To minimize the spread of the virus and the impact on vulnerable groups, contacts with serious mumps-like symptoms should be advised to call ahead before visiting their health care provider. In the event of a large community outbreak where Public Health has set up triage centres, it is appropriate for potential cases to be redirected to one of these centres. For an individual who has developed mild mumps-like symptoms not requiring medical attention, a call to Public Health would ensure that they are included in case counts for the outbreak.
Contacts that are in a health care facility should be managed using droplet precautions for the duration of their period of communicability.
6.4 Exposure Settings
The management, prevention, and control of mumps may be specific to the exposure settings affected. Management of mumps cases and contacts in three of the commonly experienced high-risk exposure settings are described below.
Gatherings apply to events of all sizes, in both private and public forums. Gatherings include social or religious functions, sports activities, organized shopping excursions, concerts, conferences, and meetings, as well as public transit. During an outbreak, events need not be cancelled, although jurisdictions may consider postponing gatherings that may pose a risk for transmission or involve vulnerable populations (e.g., well-baby clinics).
It is prudent for organizers to use these opportunities to inform participants about the potential for disease transmission and methods to minimize the spread of the disease, including immunization, practising good hand hygiene, avoiding sharing drinking glasses or utensils, covering coughs and sneezes with a tissue or forearm, and staying home when ill(17). Because of the slight but real risk of infection, exposure settings should be widely communicated to the public. Further details on risk communications are found in Section 8.0.
6.4.2 Schools/Educational Institutions
Mumps cases should be excluded from school, day care, child care, or the workplace until 5 days after the onset of symptoms. Caregivers are to be advised to keep the child away from other susceptible children and adults for the period of exclusion. Schools/educational institutions may already have exclusion policies in place; this varies depending on the affected jurisdictions. The risk of exposure should also be communicated to all staff, students, and families.
6.4.3 Health Care Settings
Health care settings include acute care and long- term care facilities, as well as home care. In these settings, a health care worker has the potential to acquire or transmit an infectious agent during the course of his or her work. Examples include nurses, physicians, support staff, home-care workers, emergency responders, students, and volunteers.
There is a small body of literature describing the impact of mumps—both isolated cases and outbreaks—in the health care setting. According to experience with mumps in hospitals during a Tennessee outbreak in 1986–1987, the introduction of mumps by either employees or patients is likely during an epidemic(18).
During the recent Nova Scotia outbreak and as of December 2007, mumps was diagnosed in 37 health care workers (personal communication: S. Clay, Nova Scotia Department of Health Promotion and Protection, Halifax, 2007) It was difficult to distinguish community versus occupational exposure, but, in the region with the majority of cases, most of the health care worker cases were related to community exposures with no clearly documented cross-transmissions to other health care workers or patients (personal communication: L. Johnston, Nova Scotia’s Capital District Health Authority). During the Iowa outbreak, there were no cases of mumps among exposed, non-immune health care workers (unpublished data: D. Diekema, 17th Annual Scientific Meeting of the Society for Healthcare Epidemiology of America, Baltimore, 2007). Evidence that mumps can have an impact in the workplace is presented in a report of a Chicago outbreak that documented 119 cases of mumps among employees and their household contacts in three Chicago workplaces(19).
The clinical diagnosis of mumps can be difficult, even in the outbreak setting (see section 5.0), as up to 30% of mumps infections are sub-clinical(20), and a number of other infectious agents can cause mumps-like illness(21). Additionally, many Canadian physicians in practice today will never have seen a case of mumps. Physicians who are familiar with mumps are a definite asset to an occupational health program. A mumps diagnosis may not be easy to make or to exclude. This difficulty becomes an important one when managing potential mumps cases and exposures in the health care setting.
While mumps is largely a self-limited illness, a small number of affected individuals will experience complications or chronic consequences of acute mumps. There are limited data on whether hospitalized or immunocompromised patients experience increased or more severe complications from mumps.
The available evidence indicates that there is a population of health care workers that is susceptible to mumps. Serologic testing during the 2007 Nova Scotia outbreak found that 83.4% of those born before 1970 and 67.7 % of those born after had laboratory evidence of immunity (unpublished data: S. Clay, 34th Annual Conference of the Association for Professionals in Infection Control and Epidemiology, San Jose, 2007). A community mumps outbreak can have considerable impact on health care settings and health care capacity. Factors contributing to the potential for mumps transmission in health care settings are as follows: the long infectious and incubation periods; a high proportion of sub-clinical and misdiagnosed cases; and a sizable population of susceptible health care workers. During a community outbreak, health care workers may be exposed in workplace settings in addition to their community exposures. In one hospital during the Iowa outbreak, there were 31 exposure events involving more than 600 health care workers (unpublished data: D. Diekema, 17th Annual Scientific Meeting of the Society for Healthcare Epidemiology of America, Baltimore, 2007). In Nova Scotia, one region evaluated 2,400 health care workers for reported contacts and furloughed 261 (personal communication: B. Walker, Nova Scotia’s Capital District Health Authority). A number of the exposures involved co-workers at meetings.
To minimize disruption in the health care setting, both the U.S. Centers for Disease Control and Prevention (CDC) and PHAC have guidelines for mumps management(22,23). In addition, the National Advisory Committee on Immunization (NACI) addresses the immunization of health care workers in some of its statements(1). All authorities emphasize the importance of assessing immunity and providing two-dose MMR vaccine to health care workers where indicated before an outbreak occurs. This strategy will result in minimal disruption to health care facilities during a community outbreak. Exclusion of health care workers who are contacts from work should be balanced with the availability of human resources and should consider the outbreak epidemiology.
Assessing the evidence of immunity can be challenging. NACI suggests cautious application of the natural immunity assumption to high-risk adults like health care workers and military personnel(16). This is further supported by Nova Scotia’s serologic results, which suggest that approximately 15% of those born before 1970 may not be immune to mumps. It is therefore recommended that birth in Canada before 1970 not be taken as evidence of immunity for health care workers and that even birth before 1957 offers only presumptive evidence of immunity(22). Furthermore, a self-reported history of mumps is not acceptable as proof of immunity. A positive IgG result may not necessarily indicate immunity, although a negative result may indicate that antibody levels are simply too low to be detected by commercially available assays. See Section 5.0 and Appendix 4 for further details on IgG tests and interpretation of test results.
In addition to the recommendations for health care settings (Table 10), algorithms to assist with the management of health care workers who are close contacts of a case of mumps and the assessment of health care workers for susceptibility to mumps are outlined in Appendix 5 (figures A and B). Management strategies in health care settings should take into account the epidemiology of the outbreak and the composition of the patient population.
|Health care settings||
Health care settings include those related to acute care, long-term care, and home care. Some health care settings may not have occupational health and infection prevention and control departments. When these are mentioned, they refer to the individual(s) responsible for occupational health and infection prevention and control for that health care setting.
A health care worker (HCW) is an individual who may have the potential to acquire or transmit an infectious agent during the course of his or her work in the health care setting (e.g., nurses, physicians, students, volunteers, home-care workers, emergency responders, and support staff ).
Pre-placement of HCWs
HCWs who are cases
HCWs who are contacts
For contact in the community (see Section 4.3) and contact in the health care setting (if unprotected face-to-face interaction within 1 metre of an infectious mumps case)
When a case of mumps is being investigated, the travel history as a potential risk factor should be considered both within and outside of Canada. The provincial/territorial health authority that identifies an infectious traveller should advise the provincial/territorial health authority of the area of residence of the case and of any known contacts, so that the authorities may follow up accordingly. The identifying health authority should also report the information to PHAC.
When cases or contacts are from a different country, the identifying provincial/territorial health authority should notify PHAC, which will contact the appropriate authority of the affected country. When international travellers associated with mumps cases or contacts are identified by the Quarantine Service or Duty Officers at an international port of entry, PHAC will notify the appropriate provincial/territorial or international public health authority.
When multiple jurisdictions are involved, it is not always clear who should report a case. Case reporting is important for describing and monitoring the epidemiology, impact, and spread of an outbreak. Therefore, during outbreaks, the jurisdiction that initially identifies and primarily handles the case is asked to report it. This decision rule is flexible and should be evaluated for each case, considering place of residence, travel itinerary, and the public health response or intervention that was implemented.
PHAC, the CDC, the World Health Organization (WHO), and the International Air Transport Association have guidelines on when and how to notify passengers and flight crew after they have been exposed to certain infectious diseases aboard international commercial aircraft(24-27). These guidelines apply mainly to highly communicable or virulent diseases such as tuberculosis, measles, or meningococcal disease, as well as other conditions listed in the Quarantine Act(28).
The appropriate public health response to exposure and transmission of mumps during commercial air travel varies. During the 2006 mumps outbreak in Iowa, the CDC initiated contact tracing of passengers sitting near an infectious passenger for flights of 5 hours or longer. The U.K. and Canada, on the other hand, generally do not follow up on the reported exposure of mumps on aircraft. In Canada, if a traveller infected with mumps has travelled by air during the infectious period (7 days before onset of symptoms to 5 days after the onset of symptoms), the local public health authorities and PHAC should be consulted. However, contact tracing through a passenger manifest is not necessary since the guidelines for tuberculosis, measles, and meningococcal disease may not apply to less infectious and self-limited diseases like mumps. In addition, follow-up is not performed, as there is no treatment or prophylactic intervention for mumps, and the passenger manifests are difficult to obtain and/or are often incomplete.
Communication of the traveller’s itinerary should be considered by the overseeing public health authority so that other jurisdictions are aware of the potential exposure, as they may have different protocols or be assessing changes in their own mumps activity. Non-nominal travel details can be shared with public health professionals across the country through the Canadian Integrated Outbreak Surveillance Centre, a secure, Webbased, alerting application.
In Canada, airlines can refuse permission to board to individuals who appear to have an infectious disease.
6.5.2 Cruise Ships
Respiratory tract infections are frequent in cruise ship settings. In the event of an identified mumps outbreak, the cruise ship’s health services would have responsibility for the traveller’s health during the cruise and would follow up with contacts according to the conveyance operator’s policy.
Ninety-six hours before port arrival, ships are to report to Canadian port authorities as to the presence and status of anyone aboard with certain communicable diseases. If a condition of quarantine or public health concern is suspected, the port authority will notify National Quarantine Services (PHAC) to meet the ship upon arrival; PHAC will then alert the provinces and territories if an outbreak is confirmed. In Canada, cruise lines can refuse permission to board to individuals who appear to have an infectious disease.
In Canada, cruise lines can refuse permission to board to individuals who appear to have an infectious disease.
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