Guidelines for the Prevention and Control of Mumps Outbreaks in Canada

Large community mumps outbreak in Manitoba, Canada, September 2016-December 2018

Background

After routine mumps immunization programs were implemented in Manitoba in the 1980s, incidence was low, with 0-9 cases of disease annually. In September 2016, a mumps outbreak began in fully vaccinated university students in Winnipeg, Manitoba.

Objective

We describe the investigation of this province-wide mumps outbreak, which lasted between September 2016 and December 2018. We present the details of public health measures implemented and challenges encountered. Possible contributing factors to the sustained transmission are also provided.

Methods

Probable and confirmed cases of mumps were investigated by public health departments using the investigation form developed for this outbreak. Confirmed mumps cases were linked to the provincial immunization registry. An outbreak response team planned and implemented control measures across the province.

Results

The outbreak began in vaccinated university students in September 2016 and spread across the province. Activity was high and prolonged in the northern remote areas. By the end of 2018, 2,223 cases had been confirmed. All age groups were affected, and incidence was highest among people aged 18-29 years. Two-dose coverage of mumps-containing vaccine in confirmed cases was close to 70%.

Conclusion

This prolonged outbreak revealed a large vulnerable population likely resulting from under-vaccination and waning vaccine-induced immunity in the absence of natural boosting from exposure to mumps virus. It is important to maintain high two-dose coverage with mumps-containing vaccines. A third dose of mumps-containing vaccine in future outbreaks may be considered.

Investigation and management of a large community mumps outbreak among young adults in Toronto, Canada, January 2017-February 2018

Background

In 2017, a mumps outbreak was identified in a cohort of 18-34 year olds in Toronto, Canada.

Objective

To describe a large community mumps outbreak in an urban centre from January 2017 to February 2018 among young adults.

Methods

A broad range of interventions were implemented in an attempt to reach the target audience; including case and contact management, vaccination clinics at schools and clinicians' offices, school exclusions, bar inspections, traditional communication strategies (including health care provider updates and posters) and newer communication strategies (including three sequential social media campaigns).

Results

A total of 143 cases of mumps were identified. Although cases' ages ranged from three to 72 years, most (76%) were 18-34 year olds, many of whom had frequented bars and local food establishments in downtown Toronto. 84% (n=120) of the cases were community-acquired. Only 16% (n=23) of the cases reported exposures in schools and post-secondary school institutions. Of those, 39% (n=56) of cases had an unknown vaccination history; 34% (n=49) were either not vaccinated or partially vaccinated with one dose of measles-mumps-rubella vaccine; and 27% (n=38) had received the recommended two doses of mumps vaccine. Determining vaccination status was a challenge, in part due to the lack of a registry. Vaccination was recommended when subjects were known to have had fewer than two doses of vaccine or had an unknown vaccination status. A social media campaign, emphasizing the risk of social activities if not protected from the mumps, yielded over 500,000 impressions from Facebook and Twitter messages and ads and an impressive engagement rate of between 1% and 10x%.

Conclusion

This was the largest mumps outbreak in Toronto in over 20 years. Among young adults, ongoing social media and traditional communication campaigns can contribute to the control of community mumps outbreaks. Encouraging vaccine uptake is desirable, but without a vaccine registry it is difficult to assess vaccination coverage among adults. Susceptible cohorts of young adults who were not adequately vaccinated pose a risk for future outbreaks. Given that almost 30% of the mumps cases were fully vaccinated with two doses of mumps-containing vaccine, even two doses may not provide complete protection.

Laboratory testing and phylogenetic analysis during a mumps outbreak in Ontario, Canada

BACKGROUND

In September 2009, a mumps outbreak originated in New York and spread to Northeastern USA and Canada. This study compares the performance of different diagnostic testing methods used in Ontario and describes molecular characteristics of the outbreak strain.

METHODS

Between September 2009 and February 2010, specimens from suspect cases were submitted to Public Health Ontario Laboratory for mumps serology, culture and/or real-time reverse-transcriptase PCR (rRT-PCR) testing. rRT-PCR-positive specimens underwent genotyping at Canada's National Microbiology Laboratory. Whole genome sequencing was performed on four outbreak and three sporadic viral culture isolates.

RESULTS

Six hundred ninety-eight patients had IgM serology testing, of which 255 (37%) had culture and rRT-PCR. Among those, 35/698 (5%) were IgM positive, 39/255 (15%) culture positive and 47/255 (18%) rRT-PCR-positive. Buccal swabs had the highest rRT-PCR positivity (21%). The outbreak isolates were identical to that in the New York outbreak occurring at the same time. Nucleotide and amino acid identity with the Jeryl Lynn vaccine strain ranged from 85.0-94.5% and 82.4-99.4%, depending on the gene and coding sequences. Homology of the HN protein, the main immunogenic mumps virus protein, was found to be 94.5 and 95.3%, when compared to Jeryl Lynn vaccine major and minor components, respectively.

CONCLUSIONS

Despite higher sensitivity than serology, rRT-PCR testing is underutilized. Further work is needed to better understand the suboptimal match of the HN gene between the outbreak strain and the Jeryl Lynn vaccine strain.

Mumps in prison: description of an outbreak in Manitoba, Canada

OBJECTIVE

There is a lack of published information on the management of mumps in a prison setting. We describe an outbreak of mumps that occurred in a medium-security correctional centre (Milner Ridge) in Manitoba, Canada.

METHODS

A case definition of mumps consistent with that in the document "Guidelines for the Prevention and Control of Mumps Outbreaks in Canada" was adopted. Cell culture, polymerase chain reaction, and serology were used for case confirmation.

RESULTS

Five confirmed cases of mumps infection were identified at the Milner Ridge Correctional Centre between January 12 and February 5, 2009. One additional confirmed case and 3 additional probable cases were identified at a second correctional centre. Outbreak control at Milner Ridge was accomplished by cohorting the affected units of the centre, providing education on mumps, deferring transfers, and monitoring for further cases. Vaccination was offered to inmates and staff on the assumption, based on average inmate age, that the majority of inmates would have previously received, at most, a single dose of mumps-containing vaccine.

CONCLUSION

An outbreak of mumps in a correctional setting was successfully contained via implementation and tailoring of basic infection control measures, and vaccination of inmates and staff. Given the relatively young age of many inmates and the parallels between prisons and dormitories, it could be argued that inmates may represent another group of individuals for whom a second dose of mumps vaccine (if not received in childhood) would be beneficial as primary prophylaxis.

Mumps virus detection during an outbreak in a highly unvaccinated population in British Columbia

OBJECTIVES

Control measures of mumps involve isolation of those symptomatic or potentially exposed. Recent guidelines have recommended shortening the isolation period from 9 days to 5 days after the onset of parotitis, despite using mainly historical evidence. In British Columbia, mumps circulated in a predominantly unvaccinated population in 2008. We compared laboratory findings between the different vaccination groups and assessed the period of mumps viral detection after onset of parotitis.

METHODS

Demographic and clinical data were collected according to guidelines during the course of the outbreak. Clinical specimens, including buccal swabs, urine, CSF and sera, were collected on a single visit upon presentation for diagnosis. Laboratory diagnosis of mumps was confirmed by either virus detection by PCR and/or isolation in cell culture from clinical specimens, or by serology.

RESULTS

Laboratory testing confirmed mumps on 85 (74%) of 115 cases by virus detection and/or serology. Thirty-nine (78%) of 50 cases had virus detected within the first 5 days after onset of parotitis, with the rate highest in specimens collected early. However, virus could be detected in 5 (56%) of 9 cases after day 5 and up to day 9.

CONCLUSION

Our study questions whether a 5-day isolation period is sufficient to prevent mumps transmission in a susceptible population. Our observations are based on single specimen submission, whereas an optimal study design would entail serial collection after presentation of parotitis, as this reflects true viral shedding. Further investigations are warranted to validate patient isolation guidelines.