Seasonal transmission dynamics of varicella in Japan: The role of temperature and school holidays

In Japan, major and minor bimodal seasonal patterns of varicella have been observed. To investigate the underlying mechanisms of seasonality, we evaluated the effects of the school term and temperature on the incidence of varicella in Japan. We analyzed epidemiological, demographic and climate datasets of seven prefectures in Japan. We fitted a generalized linear model to the number of varicella notifications from 2000 to 2009 and quantified the transmission rates as well as the force of infection, by prefecture. To evaluate the effect of annual variation in temperature on the rate of transmission, we assumed a threshold temperature value. In northern Japan, which has large annual temperature variations, a bimodal pattern in the epidemic curve was observed, reflecting the large deviation in average weekly temperature from the threshold value. This bimodal pattern was diminished with southward prefectures, gradually shifting to a unimodal pattern in the epidemic curve, with little temperature deviation from the threshold. The transmission rate and force of infection, considering the school term and temperature deviation from the threshold, exhibited similar seasonal patterns, with a bimodal pattern in the north and a unimodal pattern in the south. Our findings suggest the existence of preferable temperatures for varicella transmission and an interactive effect of the school term and temperature. Investigating the potential impact of temperature elevation that could reshape the epidemic pattern of varicella to become unimodal, even in the northern part of Japan, is required.

Exploring the Seasonal Drivers of Varicella Zoster Virus Transmission and Reactivation

Varicella zoster virus (VZV) is a herpesvirus that causes chickenpox and shingles. The biological mechanisms underpinning the multidecadal latency of VZV in the body and subsequent viral reactivation-which occurs in approximately 30% of individuals-are largely unknown. Because chickenpox and shingles are endemic worldwide, understanding the relationship between VZV transmission and reactivation is important for informing disease treatment and control. While chickenpox is a vaccine-preventable childhood disease with a rich legacy of research, shingles is not a notifiable disease in most countries. To date, population-level studies of shingles have had to rely on small-scale hospital or community-level data sets. Here, we examined chickenpox and shingles notifications from Thailand and found strong seasonal incidence in both diseases, with a 3-month lag between peak chickenpox transmission season and peak shingles reactivation. We tested and fitted 14 mathematical models examining the biological drivers of chickenpox and shingles over an 8-year period to estimate rates of VZV transmission, reactivation, and immunity-boosting, wherein reexposure to VZV boosts VZV-specific immunity to reinforce protection against shingles. The models suggested that the seasonal cycles of chickenpox and shingles have different underlying mechanisms, with ambient levels of ultraviolet radiation being correlated with shingles reactivation.

Health Impact and Cost-effectiveness Assessment for the Introduction of Universal Varicella Vaccination in Switzerland

BACKGROUND

Varicella, caused by the varicella-zoster virus, is a highly contagious infectious disease with substantial health and economic burden to society. Universal varicella vaccination (UVV) is not yet recommended by the Swiss National Immunization Program, which instead recommends catch-up immunization for children, adolescents and adults 11-40 years of age who have no reliable history of varicella or are varicella-zoster virus-IgG seronegative. The objective of this study was to perform an assessment of health impact and cost-effectiveness comparing UVV with current practice and recommendations in Switzerland.

METHODS

A dynamic transmission model for varicella was adapted to Switzerland comparing 2 base-case schedules (no infant vaccination and 10% coverage with infant vaccination) to 3 different UVV schedules using quadrivalent (varicella vaccine combined with measles-mumps-rubella) and standalone varicella vaccines administered at different ages. Modeled UVV coverage rates were based on current measles-mumps-rubella coverage of approximately 95% (first dose) and 90% (second dose). Direct medical costs and societal perspectives were considered, with cost and outcomes discounted and calculated over a 50-year time horizon.

RESULTS

UVV would reduce the number of varicella cases by 88%-90%, hospitalizations by 62%-69% and deaths by 75%-77%. UVV would increase direct medical costs by Swiss Franc (CHF) 39-49 (US $43-54) per capita and costs from a societal perspective by CHF 32-40 (US $35-44). Incremental quality-adjusted life-years per capita increased by 0.0012-0.0014. Incremental cost-effectiveness ratios for the UVV schedules versus the base-case were CHF 31,194-35,403 (US $34,452-39,100) per quality-adjusted life-year from the direct medical cost perspective and CHF 25,245-29,552 (US $27,881-32,638) from the societal perspective.

CONCLUSIONS

UVV appears highly effective and cost-effective when compared with current clinical practice and recommendations in Switzerland from both a direct medical costs perspective and societal perspective.

Cost-effectiveness of varicella and herpes zoster vaccination in Sweden: An economic evaluation using a dynamic transmission model

OBJECTIVES

Comprehensive cost-effectiveness analyses of introducing varicella and/or herpes zoster vaccination in the Swedish national vaccination programme.

DESIGN

Cost-effectiveness analyses based on epidemiological results from a specifically developed transmission model.

SETTING

National vaccination programme in Sweden, over an 85- or 20-year time horizon depending on the vaccination strategy.

PARTICIPANTS

Hypothetical cohorts of people aged 12 months and 65-years at baseline.

INTERVENTIONS

Four alternative vaccination strategies; 1, not to vaccinate; 2, varicella vaccination with one dose of the live attenuated vaccine at age 12 months and a second dose at age 18 months; 3, herpes zoster vaccination with one dose of the live attenuated vaccine at 65 years of age; and 4, both vaccine against varicella and herpes zoster with the before-mentioned strategies.

MAIN OUTCOME MEASURES

Accumulated cost and quality-adjusted life years (QALY) for each strategy, and incremental cost-effectiveness ratios (ICER).

RESULTS

It would be cost-effective to vaccinate against varicella (dominant), but not to vaccinate against herpes zoster (ICER of EUR 200,000), assuming a cost-effectiveness threshold of EUR 50,000 per QALY. The incremental analysis between varicella vaccination only and the combined programme results in a cost per gained QALY of almost EUR 1.6 million.

CONCLUSIONS

The results from this study are central components for policy-relevant decision-making, and suggest that it was cost-effective to introduce varicella vaccination in Sweden, whereas herpes zoster vaccination with the live attenuated vaccine for the elderly was not cost-effective-the health effects of the latter vaccination cannot be considered reasonable in relation to its costs. Future observational and surveillance studies are needed to make reasonable predictions on how boosting affects the herpes zoster incidence in the population, and thus the cost-effectiveness of a vaccination programme against varicella. Also, the link between herpes zoster and sequelae need to be studied in more detail to include it suitably in health economic evaluations.

Pox Parties for Grannies? Chickenpox, Exogenous Boosting, and Harmful Injustices

Some societies tolerate or encourage high levels of chickenpox infection among children to reduce rates of shingles among older adults. This tradeoff is unethical. The varicella zoster virus (VZV) causes both chickenpox and shingles. After people recover from chickenpox, VZV remains in their nerve cells. If their immune systems become unable to suppress the virus, they develop shingles. According to the Exogenous Boosting Hypothesis (EBH), a person's ability to keep VZV suppressed can be 'boosted' through exposure to active chickenpox infections. We argue that even if this hypothesis were true, immunization policies that discourage routine childhood varicella vaccination in order to prevent shingles for other people are unethical. Such policies harm children and treat them as mere means for the benefit of others, and are inconsistent with how parents should treat their children and physicians should treat their patients. These policies also seem incompatible with institutional transparency.

[Revised multidisciplinary guidelines 'Varicella'; broader indication for post-exposure prophylaxis]

Post-exposure prophylaxis (PEP) with varicella zoster immunoglobulins (VZIG) should be administered as soon as possible after exposure to the virus, but always within ten days; in the previous guidelines this was within 96 hours. In cases of perinatal exposure, PEP with VZIG should be administered to neonates if the mother develops clinical chickenpox between seven days before delivery and seven days after delivery; in the previous guidelines this was between five days before delivery and two days after delivery. A new chapter on the treatment of chickenpox has been added to the guidelines.

Descriptive epidemiology of varicella based on national surveillance data before and after the introduction of routine varicella vaccination with two doses in Japan, 2000-2017

Routine childhood immunization using two doses of the varicella vaccine was introduced in Japan in October 2014. In this study, we analyzed the data extracted from national varicella surveillance, including pediatric sentinel surveillance from 2000 to 2017 and hospitalized varicella surveillance from the 38th week of 2014 to the 37th week of 2017. Compared with the 2000-2011 baseline data, the number of varicella cases per sentinel decreased substantially by 76.6% overall and by 88.2% among children aged 1-4 years in 2017. Of 997 hospitalized patients, we found a decreasing trend in the number of cases among children aged <5 years. We also found a decreasing trend in the number of cases with complications among children aged 1-4 years. Data on the self-reported transmission sites in 35.5% (354/997) of the hospitalized varicella patients showed that transmission of varicella zoster virus (VZV) occurred frequently in household, at school for young children, in the workplace for adults, and at hospital for all age groups. Data from 29.0% (289/997) of the hospitalized patients with a self-reported source of infection showed that transmission of VZV occurred from a patient with herpes zoster (HZ) in 30.4% (88/289) of cases. Our data demonstrate a substantial decrease in the number of varicella cases in young children following introduction of routine childhood vaccination program with two-dose varicella vaccination in Japan. These data highlight the unique aspects of transmission sites across age groups and the important role of HZ cases in disease circulation.

How to hold an ethical pox party

Pox parties are a controversial alternative to vaccination for diseases such as chickenpox. Such parties involve parents infecting non-immune children by exposing them to a contagious child. If successful, infection will usually lead to immunity, thus preventing infection later in life, which, for several vaccine-preventable diseases, is more severe than childhood infection. Some may consider pox parties more morally objectionable than opting out of vaccination through non-medical exemptions. In this paper, I argue that this is not the case. Pox parties involve immediate risk of harm for children and reduce future harms, whereas opting out of vaccination places children at long-term risk of harms that increase with time, at least for some pathogens. Regarding harm to others through onward transmission of infection, this can be easily prevented in the case of pox parties-given the relatively controlled timing of infection-by quarantining attendees after the party, whereas opting out of vaccination involves risks to others that are more difficult to control. I defend three criteria for an ethical pox party: (1) that the disease is sufficiently low risk, (2) that parents consent to their child's attendance and (3) that children exposed to infection are quarantined and isolated appropriately. I argue that, if these criteria are met, pox parties are morally preferable to non-vaccination; such parties involve less risk to non-consenting others and, for some pathogens in some cases, even involve less risk for the children who participate. Thus, policies that permit non-medical exemption to vaccination should also permit ethical pox parties. Alternatively, if pox parties are not permitted, then vaccination should be mandated for those without medical contraindication.

An Outbreak of Chickenpox in a Military Field Hospital-the Implications for Biological Warfare

An outbreak of chickenpox with spread to patients and staff on the isolation ward of a British field hospital during the Gulf war is described. The implications for the design and operation of field hospital isolation units should transmissible biological warfare agents be encountered in any future conflict are discussed.

Knowledge, Attitude and Practice of Pregnant Women towards Varicella and Their Children's Varicella Vaccination: Evidence from Three Distrcits in Zhejiang Province, China

Background: The objectives of this study were to examine the knowledge, attitudes and practice (KAP) towards varicella and varicella vaccine (VarV) vaccination among pregnant women in three distrcits in Zhejiang Province, China. Methods: From 1 January to 31 March 2014, pregnant women with ≥12 gestational weeks were recruited and received a self-administrated questionnaire. The first dose of VarV (VarV1) vaccination status of children from present pregnancy was extracted at 24 months of age from Zhejiang provincial immunization information system (ZJIIS). Three variables was defined as the main outcomes, which included: (1) knowing about both the availability of VarV and the number of doses required; (2) positive attitude towards the utility of varicella vaccination; (3) the vaccination coverage of VarV1, which meant the proportion of children having received the VarV1. Counts and proportions were used to describe the socio-demographic characteristics of study participants, and their relationship with study outcomes were tested using chi-square tests in univariate analysis and logistic regression in multivariable analysis. Results: A total of 629 pregnant women participated in this study. The majority of the participants (68.0%) answered correctly about the transmission route of varicella. The proportion of participants who heard about varicella vaccination was 76.5% and 66.8% knew that VarV was currently available. Only 13.5% of the participants answered correctly that the complete VarV series needed two doses. Age, immigration status, education level, household income, and number of children of the pregnant women were significant predictors of the KAP regarding the VarV vaccination. Conclusions: The current survey indicated that optimal KAP levels and coverage on VarV vaccination were observed in three districts of Zhejiang Province. Health education programs on varicella and VarV vaccination directed towards both pre-natal and post-natal women are needed, which will result in a better attitude on vaccination of VarV and in a high coverage of VarV.

Modelling the transmission and control strategies of varicella among school children in Shenzhen, China

Objectives

Varicella (chickenpox) is a highly transmissible childhood disease. Between 2010 and 2015, it displayed two epidemic waves annually among school populations in Shenzhen, China. However, their transmission dynamics remain unclear and there is no school-based vaccination programme in Shenzhen to-date. In this study, we developed a mathematical model to compare a school-based vaccination intervention scenario with a baseline (i.e. no intervention) scenario.

Methods

Data on varicella reported cases were downloaded from the Infectious Disease Reporting Information Management System. We obtained the population size, age structure of children aged 15 or under, the class and school distribution from Shenzhen Education Bureau. We developed an Agent-Based Susceptible-Exposed-Infectious-Recovered (ABM-SEIR) Model that considered within-class, class-to-class and out-of-school transmission modes. The intervention scenario was that school-wide vaccination intervention occurred when an outbreak threshold was reached within a school. We varied this threshold level from five to ten cases. We compared the reduction of disease outbreak size and estimated the key epidemiological parameters under the intervention strategy.

Results

Our ABM-SEIR model provided a good model fit to the two annual varicella epidemic waves from 2013 to 2015. The transmission dynamics displayed strong seasonality. Our results suggested that a school-based vaccination strategy could effectively prevent large outbreaks at different thresholds.

Conclusions

There was a considerable increase in reported varicella cases from 2013 to 2015 in Shenzhen. Our modelling study provided important theoretical support for disease control decision making during school outbreaks and the development of a school-based vaccination programme.

Viral Genome Sequencing Proves Nosocomial Transmission of Fatal Varicella

We report the first use of whole viral genome sequencing to identify nosocomial transmission of varicella-zoster virus with fatal outcome. The index case patient, nursed in source isolation, developed disseminated zoster with rash present for 1 day before being transferred to the intensive care unit (ICU). Two patients who had received renal transplants while inpatients in an adjacent ward developed chickenpox and 1 died; neither patient had direct contact with the index patient.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

The prevention of varicella (chickenpox) using live attenuated varicella vaccines has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States and Australia. Many countries do not routinely immunise children against varicella and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH METHODS

We searched CENTRAL (2014, Issue 1), MEDLINE (1966 to March week 1, 2014), EMBASE (January 1990 to March 2014) and LILACS (1982 to March 2014). We searched for unpublished trials registered on the clinicaltrials.gov and WHO ICTRP websites.

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse events following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

We identified three trials involving 110 healthy children who were siblings of household contacts. The included trials varied in study quality, vaccine used, length of follow-up and outcomes measured and, as such, were not suitable for meta-analysis. We identified high or unclear risk of bias in two of the three included studies. Overall, 13 out of 56 vaccine recipients (23%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with fewer than 50 skin lesions). In the three trials, most participants received PEP within three days following exposure; too few participants were vaccinated four to five days post-exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included trial reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. We identified no RCTs for adolescents or adults. Safety was not adequately addressed.

Computational modeling of interventions and protective thresholds to prevent disease transmission in deploying populations

Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings.

Management and prevention of varicella-zoster virus infection in pregnancy: a case report and review of the literature

Primary infection with varicella-zoster virus (VZV) during pregnancy can lead to devastating outcomes for both the mother and fetus. We describe a case of VZV infection in a pregnant woman who presented at 38 weeks' gestation. We also review the literature regarding management and prevention. Varicella-zoster virus-associated pneumonia in the mother is important to recognize. Outcomes in the newborn largely are dependent on gestational age at the time of infection. Prevention is paramount to management.

Centers for Disease Control and Prevention (CDC). Notes from the field: severe varicella in an immunocompromised child exposed to an unvaccinated sibling with varicella--Minnesota, 2011

Varicella usually is a self-limited disease but can result in serious complications (e.g., encephalitis, pneumonia, sepsis, hemorrhagic varicella, and death), especially among immunocompromised persons. Implementation of the varicella vaccination program in the United States, beginning in 1995, has led to declines of >95% in varicella-related hospitalizations and deaths among populations routinely vaccinated (1).

Neonatal herpes: what lessons to learn

Vesicular rashes in neonates are challenging in terms of diagnosis and management. Herpes infection is an important diagnostic consideration. We report two illustrative neonatal cases of herpesvirus infections with vesicular rashes. Such babies may be remarkably asymptomatic. A high index of suspicion leading to a prompt diagnosis, timely quarantine measures, and institution of antiviral treatment are pivotal for desirable outcomes.

Modelling the effects of population structure on childhood disease: the case of varicella

Realistic, individual-based models based on detailed census data are increasingly used to study disease transmission. Whether the rich structure of such models improves predictions is debated. This is studied here for the spread of varicella, a childhood disease, in a realistic population of children where infection occurs in the household, at school, or in the community at large. A methodology is first presented for simulating households with births and aging. Transmission probabilities were fitted for schools and community, which reproduced the overall cumulative incidence of varicella over the age range of 0-11 years old.Moreover, the individual-based model structure allowed us to reproduce several observed features of VZV epidemiology which were not included as hypotheses in the model: the age at varicella in first-born children was older than in other children, in accordance with observation; the same was true for children residing in rural areas. Model predicted incidence was comparable to observed incidence over time. These results show that models based on detailed census data on a small scale provide valid small scale prediction. By simulating several scenarios, we evaluate how varicella epidemiology is shaped by policies, such as age at first school enrolment, and school eviction. This supports the use of such models for investigating outcomes of public health measures.

Clinical Inquiry: is it safe to vaccinate children against varicella while they're in close contact with a pregnant woman?

Yes. All healthy children without evidence of immunity to varicella who are living in a household with a susceptible pregnant woman should be vaccinated.

[Varicella during pregnancy: consequences for the mother and the newborn]

In our area, varicella is a frequent and essentially benign childhood disease. In contrast, the disease course is likely to be more severe or complicated in the adult, particularly so in the pregnant woman. There is a definite risk of congenital varicella syndrome when the chickenpox occurs during the first 20 weeks of pregnancy. This syndrome predominantly affects the skin, the subcutaneous tissue, muscles and bones, as well as the central nervous system, and can bring about major functional sequellae. In case of chickenpox occurring at the very end of pregnancy, transplacental transfer of the virus may result in a perinatal varicella disease. We propose a approach of each of these different situations.

Varicella at sea: a two-year study on cruise ships

BACKGROUND

Being highly contagious by person-to-person transmission, varicella can easily spread within the multinational population of a cruise ship and into communities ashore. The aim of the study was to report the prevalence of varicella infections in a fleet of cruise ships during a two-year period and to discuss measures to prevent and contain shipboard outbreaks.

MATERIAL AND METHODS

All probable varicella cases among passengers and crew on 34 cruise ships were registered for 2 years by the medical facilities onboard. Patients remained isolated until 6 days after rash onset. Susceptible contacts were identified and offered post-exposure prophylaxis. Crew nationality, number of vaccinated contacts, and direct vaccination costs were registered.

RESULTS

During two years 187 varicella cases (36 passengers, 151 crew) were registered and 2,685 varicella vaccinations were administered at an estimated direct vaccination cost of US $ 283,832. Of the 34 ships, only 3 reported no cases of varicella. There were 8 clusters ('outbreaks') of ≥ 5 varicella cases presenting less than 42 days apart, comprising a total of 89 patients. While > 130 nations were represented among the crew, the 151 crew cases came from 26 countries, and 88 (58%) of them came from 5 sub-tropical/tropical countries.

CONCLUSIONS

All cruise vessels must expect to encounter varicella cases or outbreaks onboard every few years. Every varicella case can start an outbreak and thus trigger several time-consuming and expensive containment measures, including isolation and mass vaccination of susceptible contacts. Mandatory pre-contract evidence of varicella immunity from all seafarers or from subgroups according to position or nationality might be worth considering. Seafarers known to be immune to varicella should always carry valid documentation while traveling.

Little Italy: an agent-based approach to the estimation of contact patterns- fitting predicted matrices to serological data

Knowledge of social contact patterns still represents the most critical step for understanding the spread of directly transmitted infections. Data on social contact patterns are, however, expensive to obtain. A major issue is then whether the simulation of synthetic societies might be helpful to reliably reconstruct such data. In this paper, we compute a variety of synthetic age-specific contact matrices through simulation of a simple individual-based model (IBM). The model is informed by Italian Time Use data and routine socio-demographic data (e.g., school and workplace attendance, household structure, etc.). The model is named “Little Italy” because each artificial agent is a clone of a real person. In other words, each agent's daily diary is the one observed in a corresponding real individual sampled in the Italian Time Use Survey. We also generated contact matrices from the socio-demographic model underlying the Italian IBM for pandemic prediction. These synthetic matrices are then validated against recently collected Italian serological data for Varicella (VZV) and ParvoVirus (B19). Their performance in fitting sero-profiles are compared with other matrices available for Italy, such as the Polymod matrix. Synthetic matrices show the same qualitative features of the ones estimated from sample surveys: for example, strong assortativeness and the presence of super- and sub-diagonal stripes related to contacts between parents and children. Once validated against serological data, Little Italy matrices fit worse than the Polymod one for VZV, but better than concurrent matrices for B19. This is the first occasion where synthetic contact matrices are systematically compared with real ones, and validated against epidemiological data. The results suggest that simple, carefully designed, synthetic matrices can provide a fruitful complementary approach to questionnaire-based matrices. The paper also supports the idea that, depending on the transmissibility level of the infection, either the number of different contacts, or repeated exposure, may be the key factor for transmission.

Data on social contact patterns are fundamental to design adequate control policies for directly transmissible infectious diseases, ranging from a flu pandemic to tuberculosis, to recurrent epidemics of childhood diseases. Most countries in the world do not dispose of such data. We propose an approach to generate synthetic contact data by simulating an artificial society that integrates routinely available socio-demographic data, such as data on household composition or on school participation, with Time Use data, which are increasingly available. We then validate the ensuing simulated contact data against real epidemiological data for varicella and parvo-virus. The results suggest that the approach is potentially a very fruitful one, and provide some insights on the biology of transmission of close-contact infectious diseases.

Varicella outbreak in a pediatric oncology ward: the Manado experience

BACKGROUND

Varicella is highly contagious and dangerous disease, especially in immunocompromised patients. Children with cancer are at increased risk of severe illness and fatal cases occur.

OBJECTIVE

To describe an outbreak of varicella among in-patient cancer children, family members and staff. Estella Children Cancer Center in Manado, Indonesia with 14 beds and a 15 bed capacity guest house for family members.

METHODS

A retrospective study of patients, family members and staff who were diagnosed with varicella based on clinical appearance was performed. Follow up was until 28 days from the last patient diagnosis' date.

RESULTS

From late February to early May 2009, varicella was affecting 4 among 8 children with leukemia, 1 family member and 1 housekeeping staff. Measurers taken after the index case were oral acyclovir both for patients and contacts, patient isolation, ward disinfection and some chemotherapy interruption. Nevertheless, a second and third wave of varicella occurred. The index case died due to encephalitis. Other patients were non-severe and cured, but one child was lost to follow up.

CONCLUSIONS

This outbreak highlights the importance of proper prevention and prompt management of varicella in immunocompromised patients. Simple and locally applicable guidelines are needed.

Using time-use data to parameterize models for the spread of close-contact infectious diseases

Social contact patterns are a critical explanatory factor of the spread of close-contact infectious agents. Both indirect (via observed epidemiologic data) and direct (via diaries that record at-risk events) approaches to the measurement of contacts by age have been proposed in the literature. In this paper, the authors discuss the possibilities offered by time-use surveys to measure contact patterns and to explain observed seroprevalence profiles. The authors first develop a methodology to estimate time-of-exposure matrices, and then they apply it to time-use data for the United States (1987-2003). Finally, the authors estimate age-specific transmission parameters for varicella, commonly known as "chickenpox," from age-specific time-of-exposure and seroprevalence data (United States, 1988-1994). The estimated time-of-exposure matrix reveals a strong element of assortativeness by age. In addition, there are peaks of exposure between people who were born one generation apart (i.e., parents and their children). Models based on the estimated age-specific transmission parameters fit the observed patterns of infection of endemically circulating varicella in a satisfactory way. The availability of time-use data for a large number of countries and their potential to supplement contact surveys make the methods developed extremely valuable and suitable for implementation in several different contexts.

[Varicella: frequent questions on treatment and recommendations for management of contacts]

Dealing with varicella often causes doubts to general practitioners and pediatricians. In this article the author summaries guidelines based on solid evidence to treat varicella and prevent the disease in susceptible contacts in different clinical scenarios and presents his personal point of view in those controversial aspects commonly resolved by the authorized opinion of experts.

Varicella zoster virus infection: clinical features, molecular pathogenesis of disease, and latency

Varicella zoster virus (VZV) is an exclusively human neurotropic alphaherpesvirus. Primary infection causes varicella (chickenpox), after which virus becomes latent in cranial nerve ganglia, dorsal root ganglia, and autonomic ganglia along the entire neuraxis. Years later, in association with a decline in cell-mediated immunity in elderly and immunocompromised individuals, VZV reactivates and causes a wide range of neurologic disease. This article discusses the clinical manifestations, treatment, and prevention of VZV infection and reactivation; pathogenesis of VZV infection; and current research focusing on VZV latency, reactivation, and animal models.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

Live attenuated varicella vaccines for the prevention of varicella (chickenpox) has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States. However, many countries do not routinely immunise children against varicella, and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2008, Issue 1); MEDLINE (1966 to February 2008); and EMBASE (January 1990 to February 2008).

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse effects following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

Three studies involving 110 healthy children who were siblings of household contacts were identified as suitable for inclusion. The studies varied in quality, study design, vaccine used, and outcomes measured and, as such, were not suitable for meta-analysis. Overall, 13 out of 56 vaccine recipients (18%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with less than 50 skin lesions). In the three studies, most subjects received PEP within three days following exposure; too few subjects were vaccinated four to five days post exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included studies reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. No RCTs for adolescents or adults were identified. However safety was not adequately addressed.

[Viral infections of the fetus and newborn infant]

Viral infections may be vertically transmitted from mother to child at different times, ranging from in utero transmission, which occurs during pregnancy, perinatal transmission, which takes place during delivery and postnatal transmission, which is usually the consequence of breastfeeding. Mother-to-child transmission, which may occur after primary, recurrent or chronic maternal infection, is potentially harmful to the fetus or the newborn since it may result in miscarriage, fetal death, congenital anomalies, intrauterine growth restriction, or severe neonatal disease. Some risk factors are thought to affect the rate of mother-to-child transmission, such as the presence of other viral infections, maternal viral load, type of infection (primary versus recurrent), obstetrical procedures (prolonged rupture of membranes, mode of delivery), social-economical conditions and breastfeeding. For some of the vertically transmitted viruses, interventions are nowadays available to prevent mother-to-child transmission, such as vaccines, passive immunization, antiviral drugs. Moreover, perinatal and postnatal infections may be prevented by the use of elective caesarean delivery and avoidance of breastfeeding.

Simian varicella in old world monkeys

Simian varicella virus (SVV) causes a natural erythematous disease in Old World monkeys and is responsible for simian varicella epizootics that occur sporadically in facilities housing nonhuman primates. This review summarizes the biology of SVV and simian varicella as a veterinary disease of nonhuman primates. SVV is closely related to varicella-zoster virus, the causative agent of human varicella and herpes zoster. Clinical signs of simian varicella include fever, vesicular skin rash, and hepatitis. Simian varicella may range from a mild infection to a severe and life-threatening disease, and epizootics may have high morbidity and mortality rates. SVV establishes a lifelong latent infection in neural ganglia of animals in which the primary disease resolves, and the virus may reactivate later in life to cause a secondary disease corresponding to herpes zoster. Prompt diagnosis is important for control and prevention of epizootics. Antiviral treatment for simian varicella may be effective if administered early in the course of infection.

Maternal chickenpox in peripartum period: a case report and review

A 30-year-old pregnant woman had skin lesions at 38 weeks of gestation. She was diagnosed as primary varicella zoster infection. Her clinical symptoms were high fever and generalized vesicles eruption. No serious maternal complication was found. The patient delivered a male baby 4 days after she developed skin lesions. The neonatal blood IgM against varicella zoster was negative. The baby was given Varicella zoster immunoglobulin within 24 hours and isolated in a neonatal care unit. The baby developed skin lesions on day 11th post delivery. Intravenous acyclovir was administered for 7 days. Finally, the baby was found to be free of severe neonatal varicella infection.

Herpes zoster in a five month old infant subsequent to intrauterine exposure to varicella infection

Herpes zoster is characterized by painful vesicular eruption in a dermatomal distribution of sensory nerves as a result of reactivation of latent herpes zoster virus in posterior root ganglia. The primary varicella infection is usually acquired in childhood and reactivation usually is seen in elderly. In rare instances herpes zoster can also occur in infancy as a result of reactivation of primary varicella infection acquired in utero or in early infancy. Here, we report a rare case of herpes zoster in a 5 month baby who acquired primary infection in utero from mother who had varicella infection at 6 months of gestation.

Comparison of the dynamics and correlates of transmission of Herpes Simplex Virus-1 (HSV-1) and Varicella-Zoster Virus (VZV) in a sample of the Israeli population

Herpes simplex virus types-1 (HSV-1) and Varicella-zoster virus (VZV) are herpes viruses that share many characteristics. However, HSV-1 spreads by close contact while VZV spreads mainly by the airborne route. In this study we compared the dynamics and correlates of transmission of these viruses in the same population. In 2000-2001, 1555 sera from an age-stratified general population sample were tested using commercial ELISA kits to measure type-specific HSV-1 and varicella IgG antibodies. The VZV seroprevalence increased rapidly with age reaching 50% seropositivity by the age of 3 years, while HSV-1 reached 50% seropositivity at the age of 14 years. The highest VZV force of infection was in the 3.5-5.5-year age group followed by the 5.5-10.5 years age group, while for HSV-1 the age specific force of infection was substantially lower and stable over the various age groups. Multivariate analysis revealed that HSV-1 seroprevalence was significantly, independently associated with age, country of birth, country of origin, ethnicity, socio-economic status and VZV sero-status. Only age, country of origin and HSV-1 sero-status were found to be associated with VZV seropositivity. In developed countries such as Israel the transmission of VZV is much quicker and less dependent on socioeconomic status as compared with HSV-1.

Deterministic SIR (Susceptible-Infected-Removed) models applied to varicella outbreaks

Deterministic SIR models were applied to simulate Susceptible-Infected-Removed and to estimate the threshold condition for varicella outbreaks in children, reported in Medellín, Colombia. The expected numbers of susceptible, infected and removed individuals were compared with observed cases from notification of varicella outbreaks to the local Board of Health and from survey data. The threshold condition was estimated by the basic reproductive ratio and by the relative removal rate, through which measures for preventing and curtailing the outbreaks were identified. The model demonstrated a reasonable fit to the observations, except in two of the six outbreaks which probably reflected under-registration of cases. In order to have prevented these outbreaks, between 4.4% and 52.9% of the susceptible population should have been vaccinated assuming an 85% vaccine effectiveness. Similarly, isolation of affected children should have been increased to between 4.3% and 44.8% per week.

Consequences of varicella in pregnancy: a report of four cases

Four infants are reported with varicella-Zoster virus (VZV) infection, whose mothers had varicella during the second-third trimester of pregnancy. Two newborns had neonatal varicella. One of them, whose mother contracted varicella 5 days before delivery, had a severe and complicated form of the disease. The infants who had herpes zoster did not have specific VZV-IgG antibodies at the onset of the disease.

CONCLUSION

These cases showed that varicella during the second-third trimester of pregnancy may have serious consequence for infants.

American Academy of Pediatrics Committee on Infectious Diseases. Prevention of varicella: recommendations for use of varicella vaccines in children, including a recommendation for a routine 2-dose varicella immunization schedule

National varicella immunization coverage using the current 1-dose immunization strategy has increased among vaccine-eligible children 19 through 35 months of age from 27% in 1997 to 88% by 2005. These high immunization rates have resulted in a 71% to 84% decrease in the reported number of varicella cases, an 88% decrease in varicella-related hospitalizations, a 59% decrease in varicella-related ambulatory care visits, and a 92% decrease in varicella-related deaths in 1- to 4-year-old children when compared with data from the prevaccine era. Despite this significant decrease, the number of reported cases of varicella has remained relatively constant during the past 5 to 6 years. Since vaccine effectiveness for prevention of disease of any severity has been 80% to 85%, a large number of cases of varicella continue to occur among people who already have received the vaccine (breakthrough varicella), and outbreaks of varicella have been reported among highly immunized populations of schoolchildren. The peak age-specific incidence has shifted from 3- to 6-year-old children in the prevaccine era to 9- to 11-year-old children in the postvaccine era for cases in both immunized and unimmunized children during these outbreaks. Outbreaks of varicella are likely to continue with the current 1-dose immunization strategy. After administration of 2 doses of varicella vaccine in children, the immune response is markedly enhanced, with > 99% of children achieving an antibody concentration (determined by glycoprotein enzyme-linked immunosorbent assay) of > or = 5 U/mL (an approximate correlate of protection) and a marked increase in geometric mean antibody titers after the second vaccine dose. The estimated vaccine efficacy over a 10-year observation period of 2 doses for prevention of any varicella disease is 98% (compared with 94% for 1 dose), with 100% efficacy for prevention of severe disease. Recipients of 2 doses of varicella vaccine are 3.3-fold less likely to have breakthrough varicella, compared with those who are given 1 dose, during the first 10 years after immunization. To achieve greater levels of immunity with fewer serosusceptible people, greater protection against breakthrough varicella disease, and reduction in the number of outbreaks that occur nationwide among school-aged populations, a 2-dose varicella immunization strategy is now recommended for children > or = 12 months of age.

Managing varicella zoster infection in pregnancy

Varicella zoster virus (VZV) infection can be serious for pregnant women and their babies, although it is rare. The implications of primary VZV infection vary with the gestational age at infection. For the mother, the risk of severe illness is greatest after mid-pregnancy, when she is relatively immunocompromised. For the fetus, the risk of congenital infection is greatest when maternal infection occurs in the first or second trimester. Maternal infection is preventable by preconception vaccination.

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.

[Atypical macular coloboma: a case report]

CLINICAL CASE

This was a 15-month-old boy who had macular retinochoroidal lesions in both eyes following maternal varicella during pregnancy.

DISCUSSION

The scars were suggestive of congenital chorioretinal infection, but because of negative serology and the clinical picture, we believe the problems are atypical macular colobomata.