Three year seroepidemiological study of varicella-zoster virus in São Paulo, Brazil

Burden of varicella in Latin America and the Caribbean: findings from a systematic literature review

BACKGROUND

Varicella is typically mild and self-limiting, but can be associated with complications and even death. The limited data available on varicella in Latin America and the Caribbean (LAC) indicate substantial burden in countries where varicella vaccine is not part of publicly funded childhood national immunization programs.

METHODS

A systematic literature review of published studies was complemented by "gray" literature on varicella incidence, complications, mortality, and economic consequences, in the absence and presence of universal varicella vaccination (UVV) in LAC.

RESULTS

Seroprevalence data indicate that varicella is usually a disease of childhood in LAC. Varicella incidence rates, while unreliable in the absence of mandatory reporting, show a trend to increased incidence due to greater urbanization and population density. The introduction of UVV in national immunization programs has led to significant reductions in varicella incidence in these areas.

CONCLUSIONS

Varicella continues to pose a substantial healthcare burden in LAC. The future introduction of UVV in additional countries is predicted to provide substantial reductions in cases, with important economic benefits. For countries that have already implemented UVV, the challenge is to maintain high rates of coverage and, where relevant, consider inclusion of a second dose to reduce breakthrough cases. Given the significant proportion of the region now implementing UVV, a regional recommendation in order to prevent any potential for age-shifts in varicella infection might be considered.

A systematic review of varicella seroprevalence in European countries before universal childhood immunization: deriving incidence from seroprevalence data

Surveillance systems for varicella in Europe are highly heterogeneous or completely absent. We estimated the varicella incidence based on seroprevalence data, as these data are largely available and not biased by under-reporting or underascertainment. We conducted a systematic literature search for varicella serological data in Europe prior to introduction of universal varicella immunization. Age-specific serological data were pooled by country and serological profiles estimated using the catalytic model with piecewise constant force of infection. From the estimated profiles, we derived the annual incidence of varicella infection (/100·000) for six age groups (<5, 5–9, 10–14, 15–19, 20–39 and 40–65 years). In total, 43 studies from 16 countries were identified. By the age of 15 years, over 90% of the population has been infected by varicella in all countries except for Greece (86·6%) and Italy (85·3%). Substantial variability across countries exists in the age-specific annual incidence of varicella primary infection among the <5 years old (from 7052 to 16 122 per 100 000) and 5–9 years old (from 3292 to 11 798 per 100 000). The apparent validity and robustness of our estimates highlight the importance of serological data for the characterization of varicella epidemiology, even in the absence of sampling or assay standardization.

Caracterização epidemiológica dos casos de varicela em pacientes internados em um hospital universitário da cidade do Recife

A varicela é uma doença cosmopolita, com contagiosidade extremamente acentuada, causada pelo vírus Varicela - Zoster. Embora considerada uma doença benigna da infância, atualmente tem-se demonstrado uma crescente incidência de complicações severas com um alto potencial de morbi-mortalidade em crianças e adultos previamente saudáveis. O trabalho tem como objetivo caracterizar o perfil epidemiológico dos casos de varicela em pacientes internados em um hospital universitário da cidade do Recife. Trata-se de um estudo do tipo descritivo-exploratório com abordagem quantitativa, realizado no período de janeiro de 2004 a janeiro de 2005 em pacientes internados por varicela no Hospital Universitário Oswaldo Cruz da cidade do Recife. Observou-se que, do total de 255 pacientes internados por varicela, 53% eram do sexo masculino; 77,3% dos casos apresentaram como complicação predominante as infecções bacterianas secundárias da pele, sendo a celulite a mais freqüente, em 48,1% dos casos; verificou-se que 2% evoluíram a óbito; constatou-se na análise dos custos e benefícios que ocorreria uma economia de R$ 61.710,00 se a população em estudo fosse vacinada. A pesquisa apresenta dados que fundamentam a importância da redução no número de casos da doença, tendo em vista que existe a possibilidade de uma evolução não satisfatória e, inclusive, evolução ao óbito. Nesse sentido, esses achados poderão nortear os gestores de saúde na adoção de condutas preventivas e no planejamento das ações de saúde.

Avaliação da suscetibilidade à varicela no paciente pediátrico portador de insuficiência renal crônica

OBJETIVO: Avaliar a suscetibilidade natural à varicela de crianças e adolescentes portadores de insuficiência renal crônica (IRC). MÉTODOS: Estudo transversal de 83 pacientes com idade acima de 18 meses e inferior a 18 anos, durante 2000 e 2001, com ritmo de filtração glomerular (RFG) abaixo de 70mL/min/1,73m², portando cartão vacinal preconizado pela Fundação Nacional de Saúde e que não receberam nenhuma dose da vacina específica. Do total, três pacientes (3/83) foram excluídos, por terem recebido doses da vacina por meio de órgãos não governamentais. A sorologia foi realizada pelo método Enzyme-Linked Immuno Sorbent Assay, considerando-se títulos sorológicos protetores acima de 100mUA/mL. RESULTADOS: Os pacientes renais crônicos tinham idade mediana de 11 anos, 66% eram masculinos, 60% procedentes do próprio município de São Paulo, com RFG médio de 33,6mL/min/1,73m². O diagnóstico clínico de varicela por profissional médico ocorreu em 39 pacientes; destes, 10% se mostraram soronegativos. Dos 80 pacientes restantes, 21 (26%) apresentaram títulos não protetores para varicela. A prevalência de suscetibilidade em menores de seis anos foi 7,93 (IC95%=3,29-19,12) vezes superior à de maiores de seis anos. CONCLUSÕES: Houve diminuição da suscetibilidade à varicela com a idade. Pacientes abaixo de seis anos foram cerca de oito vezes mais suscetíveis à varicela que os renais crônicos com idade mais avançada e duas vezes mais suscetíveis do que a população pediátrica brasileira de mesma idade.

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.

Clinical diagnosis of herpes zoster in family practice

PURPOSE

Family physicians usually diagnose herpes zoster on clinical grounds only, possibly resulting in false-positive diagnoses and unnecessary treatment. We wanted to determine the positive predictive value of the physicians' judgment in diagnosing herpes zoster and to assess the applicability of dried blood spot analysis for diagnosis of herpes zoster in family practice.

METHODS

Our study population consisted of 272 patients older than 50 years with herpes zoster (rash for less than 7 days). Dried blood spot samples were collected from all patients and sent by mail to the laboratory. Baseline measurements included clinical signs (localization, severity, and duration of rash) and symptoms (duration and severity of pain). Varicella-zoster virus antibodies were determined at baseline and 5 to 10 days later. Multivariate logistic regression was used to assess independent associations between clinical variables and serological confirmation of herpes zoster.

RESULTS

Dried blood spot analysis was possible in 260 patients (96%). In 236 the diagnosis of herpes zoster was confirmed serologically (positive predictive value of clinical judgment 90.8%; 95% confidence interval, 87.3%-94.3%). Independent clinical variables for serologically confirmed herpes zoster were severity and duration of rash at first examination.

CONCLUSION

Family physicians have good clinical judgment when diagnosing herpes zoster in older patients. Dried blood spot analysis is a logistically convenient method for serological investigation of patients in family practice, but it is rarely needed for diagnosing herpes zoster.

Reliability of information on varicella history in preschool children

OBJECTIVE

To verify how reliable is the information provided by parents about the history of varicella in their children.

METHODS

204 parents of previously healthy children attending two municipal day-care centers of São Paulo city were interviewed between August 2003 and September 2005. A standardized form was filled out with information regarding age, sex, history of varicella and other diseases, drug use and antecedent of immunization, After medical history, physical examination and checking of immunization records, 5 ml of blood were collected for ELISA (in house) varicella test. Exclusion criteria were: age less than 1 year or more than 60 months, previous immunization against chickenpox, presence of co-morbidities or recent use of immunosuppressive drugs. Data were filed in a data bank using the Excel 2003 Microsoft Office Program and stored in a PC computer. The exact Fisher test was employed to calculate sensibility, specificity, positive and negative predictive values of history of varicella informed by children's parents.

RESULTS

The age of the children varied from 12 to 54 months (median, 26 months; 49 (24%) children had positive history of varicella, 155 (76%) a negative or doubtful history. The predictive positive and negative values of the information were 90% and 93%, respectively (p = 0.0001).

CONCLUSIONS

The degree of reliability of information about history of varicella informed by parents of children attending day care centers was high and useful to establish recommendations on varicella blocking immunization in day-care centers.

Varicella zoster in children attending day care centers

OBJECTIVE

To describe morbidity associated to varicella in children attending day care centers.

METHODS

Descriptive study carried out through inquiries with parents of 664 children who acquired varicella after admission to day care centers in Taubaté (population: 244,165, census of 2004), a prosperous city in the State of São Paulo.

RESULTS

The median age was 36 months (range 6 to 80 months); 8.4% of the children had varicella before 1 year of age. The main symptoms were: exanthema (100.0%), fever (85.4%) anorexia (39.6%), and headache (15.3%). 517 children (77.9%) had at least 1 medical visit, and 80.6% received at least 1 medication; 73 (11.0%) received nonsteroidal antiinflammatory drugs, and 52 (7.8%) received antibiotics. Complications occurred in 38 children (5.7%; 95% confidence interval: 3% - 8%); 8 (1.2%) were hospitalized, and 5 (0.7%) had sequelae. Complications and hospitalizations rates were 3 times more frequent in children with less than 1 year of age than in older children. More than half of the children and of the working parents were absent from their regular activities for more than a week.

CONCLUSIONS

Varicella was associated with significant morbidity, affected younger children, was complicated in more than 5%, and left sequelae in 0.7% of children. More than 10% of the children received nonsteroidal antiinflammatory drugs, highlighting the need to warn the population about the risks of these drugs. Although varicella vaccination is not recommended for children younger than 12 months, vaccination of the children older than a year could avoid by herd immunity the transmission to babies. Brazilian public health authorities should be alerted to this issue and offer varicella vaccine to children attending day care centers.