Mumps transmission in social networks: a cohort study

Abstract

BackgroundMumps emerged among highly vaccinated populations in the Netherlands. This offered a unique opportunity to study mumps virus transmission. In particular the extent to which asymptomatic infections in vaccinated people contribute to ongoing mumps virus transmission is uncertain. Insight into this could help project the future burden of mumps in vaccinated populations. We therefore studied the relative infectiousness of symptomatic and asymptomatic cases.MethodsIn a cohort study we followed contacts of notified mumps cases (ring 1) and contacts’ contacts (ring 2) for 40 days to ascertain symptoms of mumps and social contacts by weekly diaries and questionnaires, and mumps virus infections by taking finger stick dried blood spot specimens (DBS) that were tested for mumps-specific IgG antibodies. Mumps IgG concentrations >1500 RU/ml in a single sample, a four-fold increase in IgG antibody concentration in paired samples, or a positive oral fluid PCR were defined as recent infection.ResultsWe recruited 99 contacts (40 in ring 1 and 59 in ring 2) of 10 mumps index cases. The median age of participants was 23 years (range 18–57 years), 31 (31%) were male. At study entry, DBS of 4 out of 78 (5%) participants with samples showed serological evidence of recent mumps virus infection. Three of these reported mumps symptoms. Among the 59 participants who provided DBS at the beginning and end of the follow-up period, none had serological evidence of infection during this period. Of 72 participants who provided at least one oral fluid sample, one participant (1%) who also reported mumps symptoms, was found PCR positive. Of all 99 participants, the attack rate of self-reported mumps was 4% (95% CI 1.1–10.0%). Of the 5 laboratory confirmed mumps cases, 1 reported no mumps symptoms (percentage asymptomatic 20% (95% CI 0–71%)). Compared to non-students, students had larger households and more household members who were born after 1980 (p < 0.01 and <0.01, respectively).ConclusionsWe demonstrated that this prospective cohort study design allows for inference of the proportion of asymptomatic mumps infections. Because we only detected one asymptomatic mumps virus infection, we could not assess the relative infectiousness of asymptomatic mumps. Household characteristics of students differed from non-students. This may partly explain recent mumps epidemiology in the Netherlands.

Assessing the Changes of Mumps Characteristics with Different Vaccination Strategies Using Surveillance Data: Importance to Introduce the 2-Dose Schedule in Quzhou of China

“…There were several limitations to this study: (1) all mumps cases were clinically diagnosed without laboratory confirmation. Mumps virus infection can result in symptomatic or asymptomatic infections [37], and the estimated 20-30% of asymptomatic cases were not possible to identify [3]. Mumps incidence in this study may therefore be 2) The immunization status of each mumps case was unknown, and we were unable to calculate the effectiveness of various vaccine doses as the NNDRS and ZJIIS data were disconnected.…”

Containing the Spread of Infectious Disease on College Campuses

“…However, such a large case count is unlikely, as it doubles the highest number of yearly mumps cases reported in the US in the last 20 years (38), which was 6,369 in 2016. There is little data on the percentage of asymptomatic mumps infections that would result in non-reporting, but the available evidence points to 15%– 30% (39, 40). Seroprevalence studies from the pre-vaccination era indicate a reporting rate of around 4% (41), which is strikingly similar to the MLE estimate for OSU, but it is hard to imagine such level underreporting in 2014 and in the midst of an active outbreak.…”

Mumps: MMR vaccination and genetic diversity of mumps virus, 2007–2011 in Catalonia, Spain

“…A possible explanation might be the antigenic differences between the circulating and vaccine strains (immune escape) [30, 31], or progressive loss of protective antibodies over time (waning immunity). Other authors have suggested high-density, close-contact environments such as schools or universities as likely causes [6, 9, 32].…”