Mumps Virus Detection During an Outbreak in a Highly Unvaccinated Population in British Columbia

Abstract

Mumps is an acute viral illness characterized by fever and parotitis that typically affects young children. 1 Clinical manifestations start with a non-specific prodrome, which can include malaise and headache, and are followed by painful swelling of the parotid glands. Less common presentations include epididymo-orchitis, oophoritis, pancreatitis and meningoencephalitis. Approximately half of those infected develop classical disease, the remainder having non-specific or respiratory symptoms and 15-20% being asymptomatic. 2,3 Most of those who are symptomatic recover fully. There is currently no specific antiviral treatment available, but mumps vaccine has been available since the 1960s. 4 The introduction of the scheduled mumps-measles-rubella (MMR) childhood vaccination in 1967 has resulted in a dramatic decrease of disease incidence in North America. 5 However, mumps has reemerged since 2004, with outbreaks reported in Europe, 6 US 7 and Canada. 8 These outbreaks have been documented in vaccinated populations, frequently affecting older children and young adults, suggesting that current vaccines are not adequately protective over the long term. 9 Control measures for mumps consist of immunization of susceptible populations and isolation of those symptomatic or potentially exposed. Post-exposure prophylaxis with vaccine or immunoglobulin is not known to prevent infection. 10 Recently, the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics have recommended shortening the isolation period from 9 days to 5 days after the onset of parotitis. 11 This was based on limited historical studies performed prior to the availability of mumps vaccination, and one small 2008 study in a highly vaccinated population 12 in which virus detection, hence the potential for transmission, was observed to be highest prior to the onset of parotitis and within the subsequent 5 days. This recommendation was also based in part on improved compliance among university students isolated for shorter periods (4 days) compared to those isolated for up to 9 days. 13 The Canadian guidelines for the prevention and control of mumps have similarly adopted a 5-day case isolation period. 14 A mumps outbreak occurred in a highly unvaccinated population in British Columbia (BC), Canada, from February to October 2008. Most of the affected unimmunized population belonged to a small faith-based community who opted out of scheduled vaccination. The outbreak was managed by using provincial mumps control guidelines, including programs for enhanced surveillance and public awareness, in the specific geographic region of the epidemic. After the outbreak resolved, we retrospectively utilized clin-

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

“…Our study also confirmed that rRT-PCR sensitivity varied with specimen type and was higher for buccal than oropharyngeal swabs or urine. This is consistent with previous studies showing that saliva swabs performed better than pharyngeal swabs, whereas test sensitivity was lowest for urine [ 4 , 23 , 37 ]. Similarly, Hindiyeh et al showed that RT-PCR sensitivity was higher with pharyngeal or parotid fluid than urine [ 38 ].…”

“…However, IgM serology was significantly less sensitive than both rRT-PCR and viral culture. Our observed order of assay sensitivity is consistent with large studies with > 80 laboratory confirmed cases [ 3 , 5 , 23 , 24 ]. In addition, a number of studies have shown a better sensitivity of rRT-PCR compared to IgM serology [ 4 , 25 – 32 ] and, to a lesser extent, culture [ 12 , 25 , 26 ].…”

“…Among the same population, Rota et al showed that sensitivity of rRT-PCR was higher than serology from day 0 to day 2 after symptom onset, whereas the sensitivity of serology was higher than rRT-PCR from day 3 onwards [ 6 ]. The fact that rRT-PCR yield was highest during day one to three after parotitis onset and decreased afterwards was confirmed in two other studies, using rRT-PCR [ 27 ] and RT-PCR [ 23 ], respectively.…”

Diagnostic Yield of Laboratory Methods and Value of Viral Genotyping during an Outbreak of Mumps in a Partially Vaccinated Population in British Columbia, Canada

“…Previously in BC, three outbreaks of mumps occurred in 1997, 2008, and 2011, largely affecting two populations: unimmunized faith-based communities and young adults in a susceptible cohort that received only one dose of mumps-containing vaccine as part of routine childhood immunization (11,12). Based on small hydrophobic (SH) gene sequencing, the 2008 and 2011 outbreaks were found to be caused by a genotype G strain; this is the most commonly circulating genotype identified in Europe and North America (13).…”

“…In Canada, including BC, it is recommended that specimens be collected within 5 days of symptom onset when the viral load is highest (5,12). However, mumps virus RNA can be detected in buccal swabs up to 9 days after symptom onset (11), although oral virus shedding may be limited to the first 2 to 3 days in vaccinated individuals (20)(21)(22). Simultaneous collection of a urine sample can improve the detection yield when the patient presents more than 5 days after symptom onset since mumps RNA is shed in urine longer (11).…”