Combining genomics and epidemiology to track mumps virus transmission in the United States

Unusually large outbreaks of mumps across the United States in 2016 and 2017 raised questions about the extent of mumps circulation and the relationship between these and prior outbreaks. We paired epidemiological data from public health investigations with analysis of mumps virus whole genome sequences from 201 infected individuals, focusing on Massachusetts university communities. Our analysis suggests continuous, undetected circulation of mumps locally and nationally, including multiple independent introductions into Massachusetts and into individual communities. Despite the presence of these multiple mumps virus lineages, the genomic data show that one lineage has dominated in the US since at least 2006. Widespread transmission was surprising given high vaccination rates, but we found no genetic evidence that variants arising during this outbreak contributed to vaccine escape. Viral genomic data allowed us to reconstruct mumps transmission links not evident from epidemiological data or standard single-gene surveillance efforts and also revealed connections between apparently unrelated mumps outbreaks.

Public Health Response to Imported Mumps Cases-Fort Campbell, Kentucky, 2018

Mumps is an acute viral disease caused by a paramyxovirus that presents with fever and swelling of one or more of the salivary glands. Although not generally considered a disease of military importance, mumps has been associated with outbreaks among young adults in close living quarters, potentially placing Soldiers at risk for transmission of mumps when living in congregated settings. This article reports a recent public health response to 3 imported mumps cases occurring at Fort Campbell, Kentucky, that resulted in a contact investigation for 109 close contacts across varied settings. No secondary mumps cases were identified. This report highlights the need for continuous preparation for public health emergency response, and the need to develop and maintain strong working relationships with local civilian public health assets, as well as with installation organizations, such as schools, child care centers, and public affairs resources.

Modelling the Transmission Dynamics and Control of Mumps in Mainland China

Mumps is a common childhood viral disease and children have been vaccinated throughout the world since 1967. The incidence of mumps has increased with more than 300,000 young people infected with mumps annually in mainland China since 2005. Therefore, we designed and analyzed long-term mumps surveillance data in an SVEILR (susceptible-vaccinated-exposed-severely infectious-mildly infectious-recovered) dynamic transmission model with optimized parameter values to describe the dynamics of mumps infections in China. There were 18.02% of mumps infected young adults seeking medical advice. The vaccine coverage has been insufficient in China. Young adults with frequent contact and mild infection were identified as a major driver of mumps epidemics. The reproduction number of mumps was determined 4.28 in China. Sensitivity analysis of the basic reproduction number and the endemic equilibrium was conducted to evaluate the effectiveness of mumps control measures. We propose to increase the vaccine coverage and make two doses of MMR (Measles, mumps and rubella) vaccines freely available in China.

[Mumps vaccine virus transmission]

In this work we report the mumps vaccine virus shedding based on the laboratory confirmed cases of the mumps virus (MuV) infection. The likely epidemiological sources of the transmitted mumps virus were children who were recently vaccinated with the mumps vaccine containing Leningrad-Zagreb or Leningrad-3 MuV. The etiology of the described cases of the horizontal transmission of both mumps vaccine viruses was confirmed by PCR with the sequential restriction analysis.

Environmental factors potentially associated with mumps transmission in yeshivas during a mumps outbreak among highly vaccinated students: Brooklyn, New York, 2009-2010

During 2009-2010, a large US mumps outbreak occurred affecting two-dose vaccinated 9th-12th grade Orthodox Jewish boys attending all-male yeshivas (private, traditional Jewish schools). Our objective was to understand mumps transmission dynamics in this well-vaccinated population. We surveyed 9th-12th grade male yeshivas in Brooklyn, NY with reported mumps case-students between 9/1/2009 and 3/30/2010. We assessed vaccination coverage, yeshiva environmental factors (duration of school day, density, mixing, duration of contact), and whether environmental factors were associated with increased mumps attack rates. Ten yeshivas comprising 1769 9th-12th grade students and 264 self-reported mumps cases were included. The average yeshiva attack rate was 14.5% (median: 13.5%, range: 1-31%), despite two-dose measles-mumps-rubella vaccine coverage between 90-100%. School duration was 9-15.5 h/day; students averaged 7 h face-to-face/day with 1-4 study partners. Average daily mean density was 6.6 students per 100 square feet. The number of hours spent face-to-face with a study partner and the number of partners per day showed significant positive associations (p < 0.05) with classroom mumps attack rates in univariate analysis, but these associations did not persist in multivariate analysis. This outbreak was characterized by environmental factors unique to the yeshiva setting (e.g., densely populated environment, prolonged face-to-face contact, mixing among infected students). However, these features were present in all included yeshivas, limiting our ability to discriminate differences. Nonetheless, mumps transmission requires close contact, and these environmental factors may have overwhelmed vaccine-mediated protection increasing the likelihood of vaccine failure among yeshiva students.

Mumps outbreak in Orthodox Jewish communities in the United States

BACKGROUND

By 2005, vaccination had reduced the annual incidence of mumps in the United States by more than 99%, with few outbreaks reported. However, in 2006, a large outbreak occurred among highly vaccinated populations in the United States, and similar outbreaks have been reported worldwide. The outbreak described in this report occurred among U.S. Orthodox Jewish communities during 2009 and 2010.

METHODS

Cases of salivary-gland swelling and other symptoms clinically compatible with mumps were investigated, and demographic, clinical, laboratory, and vaccination data were evaluated.

RESULTS

From June 28, 2009, through June 27, 2010, a total of 3502 outbreak-related cases of mumps were reported in New York City, two upstate New York counties, and one New Jersey county. Of the 1648 cases for which clinical specimens were available, 50% were laboratory-confirmed. Orthodox Jewish persons accounted for 97% of case patients. Adolescents 13 to 17 years of age (27% of all patients) and males (78% of patients in that age group) were disproportionately affected. Among case patients 13 to 17 years of age with documented vaccination status, 89% had previously received two doses of a mumps-containing vaccine, and 8% had received one dose. Transmission was focused within Jewish schools for boys, where students spend many hours daily in intense, face-to-face interaction. Orchitis was the most common complication (120 cases, 7% of male patients ≥12 years of age), with rates significantly higher among unvaccinated persons than among persons who had received two doses of vaccine.

CONCLUSIONS

The epidemiologic features of this outbreak suggest that intense exposures, particularly among boys in schools, facilitated transmission and overcame vaccine-induced protection in these patients. High rates of two-dose coverage reduced the severity of the disease and the transmission to persons in settings of less intense exposure.

Transmission of mumps virus from mumps-vaccinated individuals to close contacts

During a recent mumps epidemic in the Netherlands caused by a genotype D mumps virus strain, we investigated the potential of vaccinated people to spread mumps disease to close contacts. We compared mumps viral titers of oral fluid specimens obtained by quantitative PCR from vaccinated (n=60) and unvaccinated (n=111) mumps patients. We also investigated the occurrence of mumps infection among the household contacts of vaccinated mumps patients. We found that viral titers are higher for unvaccinated patients than for vaccinated patients during the 1st 3 days after onset of disease. While no symptomatic cases were reported among the household contacts (n=164) of vaccinated mumps patients (n=36), there were cases with serological evidence of asymptomatic infection among vaccinated household contacts (9 of 66 vaccinated siblings). For two of these siblings, the vaccinated index patient was the most probable source of infection. We conclude that, in this particular outbreak, the risk of a close contact becoming infected by vaccinated patients was small, but present.

The role of schools in the spread of mumps among unvaccinated children: a retrospective cohort study

BACKGROUND

In the Netherlands, epidemics of vaccine preventable diseases are largely confined to an orthodox protestant minority with religious objections to vaccination. The clustering of unvaccinated children in orthodox protestant schools can foster the spread of epidemics. School closure has nevertheless not been practiced up until now. A mumps epidemic in 2007-2008 gave us an opportunity to study the role of schools in the spread of a vaccine preventable disease in a village with low vaccination coverage.

METHODS

A retrospective cohort study was conducted among the students in four elementary schools and their siblings. The following information was collected for each child: having had the mumps or not and when, school, age, MMR vaccination status, household size, presence of high school students in the household, religious denomination, and home village. The spread of mumps among unvaccinated children was compared for the four schools in a Kaplan-Meier analysis using a log-rank test. Cox proportional hazard analyses were performed to test for the influence of other factors. To correct for confounding, a univariate Cox regression model with only school included as a determinant was compared to a multivariate regression model containing all possible confounders.

RESULTS

Out of 650 households with children at the schools, 54% completed a questionnaire, which provided information on 1191 children. For the unvaccinated children (N = 769), the Kaplan-Meier curves showed significant differences among the schools in their cumulative attack rates. After correction for confounding, the Cox regression analysis showed the hazard of mumps to be higher in one orthodox protestant school compared to the other (hazard ratio 1.43, p < 0.001). Household size independently influenced the hazard of mumps (hazard ratio 1.44, p < 0.005) with children in larger households running a greater risk.

CONCLUSION

If and when unvaccinated children got mumps was determined by the particular school the children and their siblings attended, and by the household size. This finding suggests that school closure can influence the spread of an epidemic among orthodox protestant populations, provided that social distancing is adhered to as well. Further research on the effects of school closure on the final attack rate is nevertheless recommended.

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.

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.

Multiple sclerosis in the Faroe Islands. 8. Notifiable diseases

OBJECTIVE

To seek evidence for a possible infectious origin of the type 1 epidemic of multiple sclerosis (MS) in the Faroe Islands. This began in 1943 coincident with their British military occupation throughout World War II.

MATERIALS AND METHODS

Data obtained from the Danish National Health Service were assessed for all notifiable diseases in the Faroe Islands reported from 1900 to 1977.

RESULTS

Among 38 disorders, selective increases were found for acute infectious gastroenteritis (AIGE) and paradysentery, with outbreaks in late 1940 and in 1943 shortly after the introduction and later marked influx, respectively, of British troops. Five other infections showed elevated numbers in 1941 and 1942.

CONCLUSIONS

There is a temporal association of AIGE and paradysentery in the Faroe Islands with the first arrival and later marked augmentation of British forces stationed there during the war. Rises in the incidence of other diseases in 1941-1942 seem more likely a consequence of increased foreign commercial travel by Faroese at that time.

Centers for Disease Control and Prevention (CDC). Update: mumps outbreak - New York and New Jersey, June 2009-January 2010

State and local health departments, in collaboration with CDC, continue to investigate a mumps outbreak that began in New York in June 2009. The index case occurred in a boy aged 11 years who had returned on June 17 from a trip to the United Kingdom, where approximately 7,400 reports of laboratory-confirmed mumps were received by the Health Protection Agency in 2009. He then attended a New York summer camp for tradition-observant Jewish boys, where he became symptomatic on June 28. Subsequently, other camp attendees and a staff member were reported to have mumps, and transmission continued in multiple locations when the camp attendees returned home. As of January 29, 2010, a total of 1,521 cases had been reported, with onset dates from June 28, 2009, through January 29, 2010, a substantial increase from the 179 cases reported as of October 30, 2009. The outbreak has remained confined primarily to the tradition-observant Jewish community, with <3% of cases occurring among persons outside the community. The largest percentage of cases (61%) has occurred among persons aged 7-18 years, and 76% of the patients are male. Among the patients for whom vaccination status was reported, 88% had received at least 1 dose of mumps-containing vaccine, and 75% had received 2 doses. This is the largest mumps outbreak that has occurred in the United States since 2006. Although mumps vaccination alone was not sufficient to prevent this outbreak, maintaining high measles, mumps, and rubella (MMR) vaccination coverage remains the most effective way to prevent outbreaks and limit their size when they occur.

Rapid response to a case of mumps: implications for preventing transmission at a medical research facility

OBJECTIVE

To prevent transmission among the staff and potentially among the non-human primate (NHP) colony at the U.S. Naval Medical Research Center Detachment in Peru, where an active case of mumps was discovered in a senior laboratory technician in Sep 03, 2007.

MATERIAL AND METHODS

Subjects at the research facility were interviewed and potentially susceptible contacts were tested for mumps IgG.

RESULTS

In total, 81 out of 106 staff members (76%) had close contact with the case. Only 6/81 (7%) had MMR, 33 (41%) reported having had mumps, and 8 of 45 (18%) of the potentially susceptible individuals did not have immunity (IgG > 20.0). All the susceptible, exposed individuals received MMR vaccine. There were no secondary cases and access to the NHP colony was restricted.

DISCUSSION

Immediate and thorough investigation and occupational health response were imperative in preventing secondary cases of mumps among humans and NHP.

Centers for Disease Control and Prevention (CDC). Updated recommendations for isolation of persons with mumps

Mumps, an acute vaccine-preventable viral illness transmitted by respiratory droplets and saliva, has an incubation period most commonly of 16-18 days. The classic clinical presentation of mumps is parotitis, which can be preceded by several days of nonspecific prodromal symptoms; however, mumps also can be asymptomatic, especially in young children. Mumps transmission can occur from persons with subclinical or clinical infections and during the prodromal or symptomatic phases of illness. In 2006, during a mumps resurgence in the United States, the latest national recommendations from CDC and the American Academy of Pediatrics (AAP) stipulated that persons with mumps be maintained in isolation with standard precautions and droplet precautions for 9 days after onset of parotitis. However, the existence of conflicting guidance (i.e., that the infectious period of mumps extended through the fourth day after parotitis onset) led to confusion regarding the appropriate length of isolation. In addition, during the 2006 resurgence, compliance with recommendations for isolation in university settings was substantially lower for 9 days (65%) compared with 4-5 days (86%). In 2007, after a review of the evidence supporting the 9-day isolation guidance by AAP and CDC, AAP changed its isolation guidance for health-care workers in ambulatory settings from 9 days to 5 days. In February 2008, after review of data on mumps in health-care settings, mumps viral load, and mumps virus isolation, the Healthcare Infection Control Practices Advisory Committee (HICPAC) approved changes in its recommendations related to mumps in in-patient settings. As a result, CDC, AAP, and HICPAC all now recommend a 5-day period after onset of parotitis, both for isolation of persons with mumps in either community or health-care settings and for use of standard precautions and droplet precautions. This report summarizes the scientific basis for these changes in mumps isolation guidance.

Transmission of the L-Zagreb mumps vaccine virus, Croatia, 2005-2008

We report on three cases of symptomatic transmission of the L-Zagreb mumps vaccine virus from three vaccinated children to five adult contacts. The five contact cases were parents of the vaccinated children and presented with parotitis and in one case also with aseptic meningitis. The etiology of the contacts' illness was determined by viral culture, genomic sequencing, serology and epidemiological linking. Two of the vaccinated children developed vaccine associated parotitis as an adverse event three weeks following immunization. Symptoms in contact cases developed five to seven weeks after the vaccination of the children. The five contact cases, as well as the three children with adverse events recovered completely. The children had been vaccinated with MMR vaccine produced by the Institute of Immunology Zagreb, each of them with a different lot. One of the possible explanations for these adverse events is that the very low levels of wild mumps virus circulation in the last decade, combined with waning immunity in those who received one dose of vaccine or suffered from mumps in childhood, resulted in susceptible young adults and that this unique epidemiological situation allows us to detect horizontal transmission of mumps vaccine virus.

Seasonally varying epidemics with and without latent period: a comparative simulation study

This paper studies two classes of epidemic models. These models are the standard SIR and SEIR models with time-varying periodic contact rate. The importance of the latent period is our target. When the latent period can be ignored and when it must be taken into account are the main points of our simulation. The comparison of the simulation results of our two models shows that the latent period is affecting the pattern of the dynamics of the disease. This paper addresses how model predictions are affected by the assumed form of the seasonally varying transmission rate and whether or not a latent class is included. Moreover, for some infectious diseases, using latent period leads to appearance or disappearance of some periodic solutions for the same parameter set. A key parameter for our models is the basic reproductive number R0. We have simulated our models for a set of values of parameters insuring that R0 > 1, which represent the endemic case (Greenhalgh & Moneim, 2003; Moneim & Greenhalgh, 2005a,b). Different patterns have been obtained for each of the SIR or SEIR; these patterns are representing the filtered results of the long-term behaviour of the endemic periodic solution for a range of amplitude parameter values of the periodic contact rate. So it is too important to determine which type of model SIR or SEIR is more likely to describe the actual nature of the dynamics of each disease.

Mumps resurgence prompts revised recommendations

Mumps outbreaks in 2006 served as a reminder that this often-overlooked, vaccine-preventable disease is still a threat. The outbreaks were concentrated in Iowa but affected several other states in the Midwest. As clinicians and public health officials considered Minnesota's vulnerability to a mumps outbreak, they discovered gaps in immunization recommendations and other problems. Increased surveillance efforts uncovered the limitations of serology-based diagnostic testing for mumps. This article summarizes the epidemiology of the recent outbreaks, the issues that arose during the public health response to them, and resulting changes in recommendations for mumps prevention and control.

Two successive outbreaks of mumps in Nova Scotia among vaccinated adolescents and young adults

BACKGROUND

Before the widespread use of vaccine, mumps was the most common cause of viral meningitis (up to 10% of mumps infections). Vaccination programs have resulted in a drop of more than 99% in the number of reported mumps cases in the United States and Canada. Although rare in Canada, outbreaks have recently occurred throughout the world, including a large outbreak in the United Kingdom, where more than 56,000 cases were reported in 2004-2005.

METHODS

Two recent outbreaks in Nova Scotia were investigated by public health officials. Cases were defined by laboratory confirmation of infection (i.e., isolation of mumps virus by culture) or clinical diagnosis in people epidemiologically linked to a laboratory-confirmed case. The people infected were interviewed to determine possible links and to identify contacts. Mumps virus was cultured from urine and throat specimens, identified via reverse-transcriptase polymerase chain reaction (RT-PCR) and subjected to phylogenetic analysis to identify the origin of the strain.

RESULTS

The first outbreak involved 13 high-school students (median age 14 yr): 9 who had previously received 2 doses of measles-mumps-rubella vaccine (MMR) and 4 who received a single dose. The second outbreak comprised 19 cases of mumps among students and some staff at a local university (median age 23 yr), of whom 18 had received only 1 dose of MMR (the other received a second dose). The viruses identified in the outbreaks were phylogenetically similar and belonged to a genotype commonly reported in the UK. The virus from the second outbreak is identical to the strain currently circulating in the UK and United States.

INTERPRETATION

The predominance in these outbreaks of infected people of university age not only highlights an environment with potential for increased transmission but also raises questions about the efficacy of the MMR vaccine. The people affected may represent a "lost cohort" who do not have immunity from natural mumps infection and were not offered a 2-dose schedule. Given the current level of mumps activity around the world, clinicians should remain vigilant for symptoms of mumps.

Centers for Disease Control and Prevention (CDC). Exposure to mumps during air travel--United States, April 2006

The state of Iowa has been experiencing a large mumps outbreak that began in December 2005. 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. 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.

Centers for Disease Control and Prevention (CDC). Mumps outbreak at a summer camp--New York, 2005

On July 26, 2005, the Sullivan County Health Department (SCHD) and the New York State Department of Health (NYSDOH) were notified of a cluster of cases of parotitis among campers and staff members at a summer camp. An investigation conducted by NYSDOH identified 31 cases of mumps, likely introduced by a camp counselor who had traveled from the United Kingdom (UK) and had not been vaccinated for mumps. This report summarizes the results of the subsequent investigation by NYSDOH, which determined that, even in a population with 96% vaccination coverage, as was the case with participants in the summer camp, a mumps outbreak can result from exposure to virus imported from a country with an ongoing mumps epidemic.

Pregnancy outcome following infections by coxsackie, echo, measles, mumps, hepatitis, polio and encephalitis viruses

Women may be infected during pregnancy with infectious agents that are often passed unnoticed; however, the causative agent may still traverse the placenta and infect the developing embryo and fetus. Several of these agents (i.e. rubella, cytomegalovirus or Toxoplasma Gondii) may cause severe fetal damage, but most other infections in pregnancy seem to be much less dangerous to the fetus. In this review we discuss the effects of several viral infections during pregnancy where the effects on the developing embryo and fetus are infrequent, but they may sometimes cause severe neonatal disease. The following viruses are discussed: coxsackie and echoviruses, measles and mumps, polioviruses, Japanese and Venezuelan equine encephalitis viruses, West Nile virus and hepatitis viruses A, B, C, D and E. Coxsackie B virus may cause an increase in early spontaneous abortions and rarely, fetal myocarditis; echoviruses do not seem to damage the fetus; measles and mumps may cause increased early and late fetal death and neonatal measles or mumps. The viruses affecting the nervous system may increase early and late spontaneous abortions and, rarely, cause severe damage to the fetal brain. Hepatitis B virus has a high rate of vertical transmission causing fetal and neonatal hepatitis. Hepatitis A, C and E are rarely transmitted trans-placentally; if transmitted, they may cause hepatitis. There is no evidence that immunization in pregnancy against these diseases (with attenuated viruses) may adversely affect pregnancy outcome.

Increasing incidence of mumps in Scotland: options for reducing transmission

BACKGROUND

There has been a dramatic increase in mumps in Scotland since November 2003, with cases primarily in adolescents and young adults.

OBJECTIVES

This paper describes mumps epidemiology in Scotland, undertakes a risk assessment and considers option for reducing transmission.

RESULTS

Mumps is primarily a risk for the 13-25 year age group, as they have neither been offered two routine doses of measles, mumps and rubella MMR vaccine, nor been exposed to wild virus. Transmission is facilitated by a high degree of social mixing, with enclosed settings (school, universities etc.) being higher risk. On the basis of susceptibility and risk of transmission, three categories of higher (17-20 years), intermediate (21-22; 15-16 years), and low (23-25; 13-14 years) risk were defined, all in higher risk enclosed settings. Herd immunity would be very difficult to achieve, as it would require unrealistically high MMR uptake (an additional 45-80% in 17-20 year olds). A risk management strategy of reducing transmission and decreasing the likelihood of outbreaks was therefore proposed. Action would be targeted at the higher risk group (17-20 years) in higher risk settings. Three options were considered: do nothing; opportunistic immunisation through GPs; a mass campaign. The 'do nothing' option was discounted. The preferred option was to alert GPs to the need to offer MMR vaccine to 17-20 year olds in higher risk settings. The rationale for this was that it had the lowest cost, avoided disruption to services, and primarily that it would reduce the probability of mumps transmission in higher risk settings.

CONCLUSIONS

The Chief Medical Officer issued a letter to all health professionals in Scotland encouraging them to offer MMR vaccine to 13-15 year olds, who had not previously received two doses, and particularly those aged 17-20 years in higher risk settings.

Protracted mumps encephalitis with good outcome

There is limited published information regarding the outcome of patients with prolonged encephalitis. This report details the case of a patient with an encephalitic illness with a protracted period of coma and a favourable outcome. Extensive investigation revealed seroconversion for mumps infection. A household contact had measles, mumps, rubella (MMR) vaccination 10 days prior to his presentation.

Horizontal transmission of the Leningrad-3 live attenuated mumps vaccine virus

Here we describe symptomatic transmission of the Leningrad-3 mumps vaccine virus from healthy vaccinees to previously vaccinated contacts. Throat swab and serum samples were taken from six symptomatic mumps cases and from 13 family contacts. Assessment of serum IgG and IgM anti-mumps virus antibodies and IgG avidity testing was performed using commercial test kits. Sera neutralizing antibodies were measured by plaque reduction neutralization assay using the L-3 vaccine mumps virus as the target. All six of the symptomatic mumps cases and three contact subjects tested positive for mumps by RT-PCR. The genomic sequences tested (F, SH and HN genes) of all nine of these samples were identical to the L-3 mumps vaccine strain. All 13 contacts were asymptomatic; however clear serological evidence of mumps infection was found in some of them. The likely epidemiological source of the transmitted L-3 mumps virus was children who were recently vaccinated at the schools attended by the six symptomatic mumps patients described here. The L-3 mumps vaccine virus can be shed and transmitted horizontally, even to subjects previously vaccinated with the same virus.

Estimation of effective reproduction numbers for infectious diseases using serological survey data

The effective reproduction number of an infection, denoted Re, may be used to monitor the impact of a vaccination programme. If Re is maintained below 1, then sustained endemic transmission of the infection cannot occur. In this paper we discuss methods for estimating Re from serological survey data, allowing for age and individual heterogeneity. We describe semi-parametric and parametric models, and obtain an upper bound on Re when vaccine coverage and efficacy are not known. The methods are illustrated using data on mumps and rubella in England and Wales.

[Risks for measles and mumps in recruits of the Croatian army]

In order to estimate the transmission risk of measles and mumps viruses and a possible change in the strategy of vaccination against these infectious diseases, seroprevalence of antibodies to measles and mumps was determined in the population of young adults, i.e. in the recruits of the Croatian Army. Factors that may influence the state of immunity were analyzed as well. The study was performed during 1995 and 1996, comprising a total of 300 recruits. The serological part of the study included 260 conscripts. The status of antibodies was evaluated using commercially available ELISA tests for the detection of IgG antibodies in blood. Seronegativity rates measured 40.80% for measles and 8.80% for mumps. With regard to specific age groups (18-19; 20-24; over 25) seronegativity rates were similar for both diseases in all subjects. It has been confirmed by this study that the place of birth and residence does not have any significant influence upon the rate of infections in the recruits. The results of the study show that there is a very high risk of measles and mumps infection in the military. This finding indicates that the introduction of additional vaccination for the high-risk population groups should be considered, against measles in particular. The detected differences in the degree of immunity to measles and mumps (vaccination of which is performed simultaneously) indicate a need for additional epidemiological and serological studies that should be performed using other laboratory techniques. The fact that soldiers do not have medical records on vaccination, and that anamnestic data on disease contraction and vaccination are unreliable, suggests that the regulations on the keeping of vaccination records in Croatia should be implemented in a more consistent way.

Modeling measles, mumps, and rubella: implications for the design of vaccination programs

Mathematical models of disease transmission are being used increasingly in the design of population-based vaccination programs. Their use is illustrated in a review of some modeling studies that have implications for the use of measles, mumps, and rubella vaccine. Investigations of vaccination strategy options yield predictions for effectiveness and cost-effectiveness analyses. A quantitative understanding of the factors affecting disease transmission enables the setting of targets for vaccination programs and underpins disease elimination initiatives.

The outbreak of mumps in a small island in Japan

A major mumps outbreak occurred on a small island, Ikeshima. in Nagasaki Prefecture from August 1994 to February 1995. There were 236 patients with the mumps at Ikeshima Miners' Hospital during that period. The Measles-Mumps-Rubella (MMR, Toitsukabu) vaccination coverage in the 43 children at the nursery school was 65.1% and it was 61.9% in the 21 children aged 4-5 years not attending the nursery school. Coverage was 66.6% in the 63 kindergarten students and 53.7% in 56 first-graders. The overall MMR vaccination coverage among these children was 61.7% (113/183) from 1989 to 1992. Children from the second grade to junior high school received monovalent mumps vaccine, Torii strain. None received Zishakabu MMR. The age of the patients ranged from 1 to 43 years, with a mean of 9.1 years. The majority (77.5%) were primary school children. The attack rates for vaccinated and unvaccinated children in grades one to six were: 6.7% (2/30) and 88.5% (23/26), 25% (3/12) and 44.1% (30/68), 11.1% (1/9) and 64.4% (29/45), 25% (2/8) and 60% (45/79), 22.2% (2/9) and 35.9% (28/78). 0% (0/5) and 24.7% (18/73), respectively. The overall frequency in the primary school was 41.4% (183/442 children). The frequency in the nursery school for children aged 4-5 years was 14.0% (6/43). It was 17.5% (11/63) in children aged 5-6 years in the kindergarten, 5.2% (11/213) in children not attending school with an age range of 1-5 years, and 4.2% (10/237) in junior high school students. Although the frequencies of MMR coverage for the nursery school children and kindergarteners were not high enough to eradicate mumps outbreaks, the MMR vaccination program was thought to have influenced the low frequency of mumps among the children. Close physical interactions among the first-graders would have contributed to their high frequency of mumps. Some patients presented with suspected mumps parotitis several times, but no such serological confirmation of reinfection was obtained.

Common infectious diseases

Many of the common infectious diseases of humans are highly transmissible, and there is ample opportunity within the dental office for spread of these infections between patients and staff. Adherence to universal infection control procedures, however, introduced to deal with the threat posed by unknown carriers of bloodborne viruses, also greatly limits spread of the more common infectious agents described in this article.

Nosocomial mumps: report of an outbreak and its control

BACKGROUND

Mumps is a relatively uncommon disease in the United States, and nosocomial transmission of mumps is rare.

METHODS

When a recently arrived Mexican immigrant became ill with mumps in a pediatric hospital in the United States, control measures and careful secondary case surveillance were instituted. Outbreak control included isolation of the patient with symptoms, seclusion of patients potentially incubating mumps virus, and immunization of susceptible patients and health care workers.

RESULTS

A 3-year-old patient showed symptoms of mumps 18 days after onset of illness in the index patient. Two employees, a physical therapist and a nurse, became ill with mumps 20 and 28 days after the onset of illness in the index patient. No other hospital or community cases of mumps were identified.

CONCLUSIONS

Outbreak control measures were incompletely successful in stopping the spread of mumps. Preadmission immunization of all patients and mumps-specific screening and vaccination of hospital employees might be indicated in such a situation, but such measures are neither easy nor inexpensive.

Sustained transmission of mumps in a highly vaccinated population: assessment of primary vaccine failure and waning vaccine-induced immunity

From January to July 1991, an outbreak of mumps occurred in Maury County, Tennessee. At the primarily affected high school, where 98% of students and all but 1 student with mumps had been vaccinated before the outbreak, 68 mumps cases occurred among 1116 students (attack rate, 6.1%). Students vaccinated before 1988 (the first year mumps vaccination was required for school attendance in Tennessee) may have been at greater risk of mumps than those vaccinated later (65[6.1%] of 1001 vs. 2[2.2%] of 89; risk ratio, 2.9; 95% confidence interval, 0.7-11.6). Of 13 persons with confirmed mumps who underwent serologic testing, 3 lacked IgM antibody in well-timed acute- and convalescent-phase serum specimens. Vaccine failure accounted for a sustained mumps outbreak in a highly vaccinated population. Most mumps cases were attributable to primary vaccine failure. It is possible that waning vaccine-induced immunity also played a role.

The risk of measles, mumps, and varicella among young adults: a serosurvey of US Navy and Marine Corps recruits

OBJECTIVES

To assess the risk of epidemic transmission and to guide immunization policy, the seroprevalence of antibody to measles, mumps, and varicella was determined in a group of young adults.

METHODS

A cross-sectional study of 1533 US Navy and Marine Corps recruits was conducted in June 1989. Antibody status was determined with commercially available enzyme-linked immunosorbent assays.

RESULTS

Direct sex and race adjustment to the 15- to 29-year-old US population resulted in seronegativity rates of 17.8% for measles, 12.3% for mumps, and 6.7% for varicella. Measles and mumps seronegativity rates were higher among Whites whereas varicella seronegativity was higher among non-Whites. Recruits enlisting from outside the 50 US states, especially those from island territories, were more likely to lack varicella antibody. The sensitivity of a positive history of vaccination or disease in predicting antibody status was less than 90% for all diseases.

CONCLUSIONS

These results suggest a continued potential for epidemics, especially of measles, and the need for mandatory immunization policies. Immigrants to the United States, especially those from island territories, may be a high-risk group that could benefit from varicella vaccination.

Thrombocytopenia in a case of neonatal mumps infection: evidence for further clinical presentations

We report a rare case of congenital mumps infection in a newborn girl. Her mother developed bilateral parotitis beginning the day of the delivery. The child was subsequently severely ill and suffered from fever, splenomegaly and thrombocytopenia, however, without parotitis nor pancreatic involvement. Both mother and child recovered well with symptomatic treatment. A review of the literature shows that clinical mumps is rare and usually benign in neonates. However, severe respiratory distress may occur. The recent appearance of mumps outbreaks in adolescents and young adults calls for a reinforcement of mumps vaccination and should prompt an immunological assessment of pregnant women after exposure.

Viral infections in the dental setting: potential effects on pregnant HCWs

Occupational exposure of pregnant health care workers to infectious diseases may cause a variety of effects. This article reviews potential effects of viral infections in pregnant health care workers by pathogens transmittable in a dental setting.

Vaccine safety versus vaccine efficacy in mass immunisation programmes

In community-wide immunisation programmes against childhood infections there is a conflict between the interests of the individual (vaccine safety and efficacy) and the interests of the community (vaccine uptake and level of herd immunity). Studies suggesting that the complication rate is greater with the high efficacy Urabe Am 9 mumps vaccine than with the lower efficacy Jeryl Lynn vaccine, have led to concern about whether the higher efficacy mumps vaccine should be introduced or retained in nationwide mass immunisation programmes. We describe the use of a mathematical model to assess benefits and risks to both individual and community, and illustrate this method by reference to immunisation programmes based on these vaccines. On the basis of current epidemiological data on viral transmission and vaccine coverage in England and Wales, data on vaccine-associated and infection-associated complication rates, and vaccine efficacies estimated from clinical trials, our analyses suggest there is little to choose between the two vaccines, but that overall performance depends on the level of vaccine coverage in a defined population. In community-based programmes, the greater apparent safety of the Jeryl Lynn vaccine (fewer vaccine-induced complications) is offset by the greater apparent efficacy of the Urabe Am 9 vaccine (fewer complications due to natural infection). The findings suggest that it may not always be in the interests of the community to use the vaccine with the lowest complication rate.