Social epidemiology of chickenpox in two British national cohorts

Childhood infectious diseases and old age cognitive functioning: a nationally representative sample of community-dwelling older adults

BACKGROUND

Cumulative evidence suggests that health-related risk factors during midlife and old-age are associated with cognitive impairment. However, studies are needed to clarify the association between early-life risk factors and impaired cognitive functioning to increment existing knowledge.

OBJECTIVE

To examine the association between childhood infectious diseases and late-life cognitive functioning in a nationally representative sample of older adults.

PARTICIPANTS

Eligible respondents were 2994 community-dwelling individuals aged 65-85.

MEASUREMENTS

Cognitive functioning was assessed using the Mini-Mental State Examination (MMSE). Childhood infectious diseases (i.e. chicken pox, measles, and mumps) were self-reported. The study covariates were age, sex, highest educational level achieved, smoking status, body mass index, and depression. The primary statistical analysis examined the association between the number of childhood infectious diseases and total MMSE scores, accounting for all study covariates. Regression models of progressive complexity were examined for parsimony. The robustness of the primary results was tested in 17 sensitivity analyses.

RESULTS

The most parsimonious model was a linear adjusted model (Bayesian Information Criterion = 12646.09). Late-life cognitive functioning significantly improved as the number of childhood infectious diseases increased (β = 0.18; 95% CI = 0.11, 0.26; p < 0.001). This effect was not significantly attenuated in all sensitivity analyses.

CONCLUSION

The current study results are consistent with prior ecological findings indicating that some childhood infectious diseases are associated with better cognitive functioning in old-age. This points to an early-life modifiable risk factor associated with older-life cognitive functioning. Our results may reflect selective mortality and/or beneficial effects via hormetic processes.

Epidemiology and factors influencing varicella infections in tropical countries including Sri Lanka

Varicella zoster virus (VZV) infections occur worldwide but the epidemiology differs between different geographical regions. Epidemiology of varicella is partly understood in tropical and subtropical regions. Various hypotheses showing differences in exposure rates in different age groups have been proposed. Exposure to VZV during late childhood or adolescent stage causes high morbidity, especially in high school children, university students and young work force in tropical nations. Exposure to VZV infection or sero-prevalence rates through anti-VZV immunoglobulin G appears to be lower in Sri Lanka, similar to other tropical countries prior to the millennium. In contrast, a more recent study in a group of antenatal women showed a relatively higher exposure rate to VZV when compared to the exposure rates prior to 2004 in Sri Lanka. Climatic factors, socioeconomic conditions, mobility and cultural practices appear to play a role in the differences in the exposure rates to VZV infection in the tropics. In most tropical Asian countries including Sri Lanka, routine vaccination against varicella is not carried out. Individuals with negative history for varicella take the vaccine when there is a necessity. Medical and nursing students take the vaccine prior to their clinical training to avoid adulthood varicella.

Successes and challenges in varicella vaccine

Varicella is a highly contagious disease caused by primary infection with varicella zoster virus (VZV). VZV infection, as well as varicella vaccination, induces VZV-specific antibody and T-cell-mediated immunity, essential for recovery. The immune responses developed contribute to protection following re-exposure to VZV. When cell-mediated immunity declines, as occurs with aging or immunosuppression, reactivation of VZV leads to herpes zoster (HZ). It has been almost 20 years since universal varicella vaccination has been implemented in many areas around the globe and this has resulted in a significant reduction of varicella-associated disease burden. Successes are reviewed here, whilst emphasis is put on the challenges ahead. Most countries that have not implemented routine childhood varicella vaccination have chosen to vaccinate high-risk groups alone. The main reasons for not introducing universal vaccination are discussed, including fear of age shift of peak incidence age and of HZ incidence increase. Possible reasons for not observing the predicted increase in HZ incidence are explored. The advantages and disadvantages of universal vs targeted vaccination as well as different vaccination schedules are discussed.

Seroprevalences of varicella-zoster virus, herpes simplex virus and cytomegalovirus in a cross-sectional study in Mexico

We estimated the seroprevalences of varicella-zoster virus (VZV), herpes simplex virus (HSV) and cytomegalovirus (CMV) in this cross-sectional database study. Serum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1-70 years between January and October 2010. Serological assays for the determination of antibodies against VZV, HSV and CMV were performed. The overall seroprevalences of VZV, HSV-1, HSV-2 and CMV were 85.8%, 80.9%, 9.9% and 89.2%, respectively. Seroprevalences of VZV, HSV-1 and CMV were comparable between males and females. For HSV-2, although the seroprevalence rate was higher in females when compared to males, this difference in seroprevalence was not statistically significant. Seroprevalence rates for VZV, HSV-1, HSV-2 and CMV increased with age (p-value<.0001). Differences in seroprevalence rate for VZV by socioeconomic status (SES) were significant (p-value<0001). Results of the serological analyses reported high VZV seroprevalence, indicating high transmission in the Mexican population with children and adolescents at risk of acquiring VZV. Global HSV-1 seroprevalence was high, especially in adults. HSV-1 and HSV-2 seroprevalences were consistently higher in women than men, particularly for HSV-2. CMV seroprevalence was higher in Mexico when compared to developed countries. Seroepidemiological data on VZV supports the fact that varicella vaccination may serve as an alternative effective solution to reduce transmission in the Mexican population. For CMV and HSV, since no vaccines are available, activities to reduce transmission are important to reduce the risk of complications and therefore need to be considered.

Social epidemiology of a large outbreak of chickenpox in the Colombian sugar cane producer region: a set theory-based analysis

There are few social epidemiologic studies on chickenpox outbreaks, although previous findings suggested the important role of social determinants. This study describes the context of a large outbreak of chickenpox in the Cauca Valley region, Colombia (2003 to 2007), with an emphasis on macro-determinants. We explored the temporal trends in chickenpox incidence in 42 municipalities to identify the places with higher occurrences. We analyzed municipal characteristics (education quality, vaccination coverage, performance of health care services, violence-related immigration, and area size of planted sugar cane) through analyses based on set theory. Edwards-Venn diagrams were used to present the main findings. The results indicated that three municipalities had higher incidences and that poor quality education was the attribute most prone to a higher incidence. Potential use of set theory for exploratory outbreak analyses is discussed. It is a tool potentially useful to contrast units when only small sample sizes are available.

Why carry out a longitudinal birth survey?

In spite of technological progress throughout the world, ill health, both physical and mental, is widespread - but much of this is preventable. With rapid globalization, populations in both industrialised and developing countries are being exposed to various stresses and to new environmental factors, such as those related to climate change and to an increasing range of chemicals of unknown effect. There is substantial evidence that exposures to environmental risk factors in pregnancy and childhood have a major influence on health and development even into adulthood and future generations. In this paper we discuss the importance of longitudinal studies in identifying the processes underlying health and developmental problems and thus, by using the strengths of birth cohort studies, identifying preventative and other strategies which will protect public health from adverse environmental influences.

Analysis of social epidemiology research on infectious diseases: historical patterns and future opportunities

BACKGROUND

Despite the many triumphs of biomedical research over infectious diseases, human pathogens continue to impact profoundly populations deprived of social resources. Correspondingly, health researchers have advocated a social determinants approach to the study and prevention of infectious diseases. However, it is unknown whether this call has resulted in an increase in the number of studies examining social determinants of infectious outcomes.

METHODS

Research on social determinants of infectious diseases was systematically quantified by assessing temporal trends in the published literature using MEDLINE, PsycINFO and ISI Web of Science.

RESULTS

Results of the literature review spanning 1966-2005 show that socially related citations increased an annual average of 180.3 for neuropsychiatric conditions, 81.9 for chronic conditions, 44.7 for sexually transmitted diseases and 18.9 for non-sexually transmitted infectious diseases (p<0.0001). Of the 279 publications found to employ the term "social epidemiology", 15 (5.4%) investigated infectious outcomes.

CONCLUSIONS

The results of the literature review suggest a paucity of social research on infectious diseases. There is a need for increased dialogue and collaboration between infectious disease epidemiologists and social epidemiologists.

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.

Varicella seroprevalence and molecular epidemiology of varicella-zoster virus in Argentina, 2002

There is limited data on immunity against varicella-zoster virus (VZV) in adults in different parts of Argentina, and it is not known which VZV strains are circulating in Argentina. The objectives of this study were as follows: (i) to evaluate seroprevalence of varicella among adults, assessing the accuracy of clinical history and determining the sociodemographic factors associated with seropositivity; and (ii) to determine the VZV strains circulating in Argentina. A cross-sectional serological survey enrolling 2,807 women aged 15 to 49 years attending public health-care settings in four cities in Argentina (i.e., Buenos Aires, Salta, Mendoza, and Rosario) and one rural area was conducted from August to November 2002. Specimens for identification of VZV strains were obtained from vesicular lesions from 13 pediatric patients with varicella from different areas of the country. PCR amplification was used for genotyping. The overall seroprevalence of varicella antibodies was 98.5% (95% confidence interval, 98.0 to 98.9), ranging from 97.2% in central Buenos Aires to 99.3% in southern Buenos Aires and Salta. Varicella seroprevalence increased with age. Crowding and length of residence in the same place were associated with seropositivity. The positive predictive value of varicella history for immunity to varicella was 99.4%; however, the negative predictive value was 2.5%. The European genotype was identified in all viral specimens. In Argentina, seroprevalence in women more than 15 years old was high regardless of the area of residence. Negative or uncertain varicella history was not a good predictor of immunity. VZV genotype was stable in all areas of the country.

Cost containment analysis of childhood vaccination against varicella in Israel

OBJECTIVES

The low cost of safe and effective vaccines prompted a cost-containment evaluation of a nationwide vaccination campaign against varicella.

METHODS

A model incorporating demographic, epidemiologic and economic data from Israeli sources (supplemented by data from International literature) was constructed to estimate the decrease in morbidity and the consequent reductions in treatment costs and time-off work of a nationwide programme vaccinating children at 12 months.

RESULTS

A policy of aiming to immunize a cohort of all 1-year-olds in Israel in the year 2002, for an annual cost of $1.10 million to the health services and $1.27 million to society (including lost work and transport costs), would reduce the number of cases of varicella during the lifetime of a cohort from 123,984 to 10,170 cases. This morbidity reduction would reduce national expenditures by $1.80 million in health service resources alone and by $24.5 million to society, mainly due to inaverted work absences. In addition an estimated 0.93 lives, representing 38.6 life years will be saved in the cohort.

CONCLUSIONS

Under an assumption of neutrality relating to the potential effects of vaccination on herpes zoster virus, our model based calculations show that a national varicella vaccination programme is likely to be cost saving, not only from a societal perspective but also from the narrower health service perspective.

A seroepidemiologic survey of the prevalence of varicella-zoster virus in the pediatric population in two university hospitals in Brazil

BACKGROUND

Varicella-zoster virus (VZV) is an alpha-herpesvirus causing varicella (chickenpox) and herpes zoster (shingles). Varicella results from primary VZV infection, and is a common childhood illness associated with fever and a generalized, pruritic, vesicular eruption. Herpes zoster is caused by VZV reactivation later in life (most cases after the fifth decade), and is characterized by a localized, painful, and vesicular eruption involving one or adjacent dermatomes. The incidence of herpes zoster increases with age and immunosuppression.

OBJECTIVE

To estimate the seroprevalence of VZV in the Brazilian pediatric population by evaluating the prevalence of specific antibodies to VZV in children from two university hospitals in the state of Rio de Janeiro.

METHODS

A population composed of 160 children derived from two university hospitals in the state of Rio de Janeiro was included in the study. All patients completed a questionnaire regarding their socio-epidemiologic characteristics, and a complete physical examination was performed. All blood samples were screened using a commercial enzyme-linked fluorescent assay (ELFA) kit, specific for the detection of immunoglobulin G (IgG) antibodies to VZV.

RESULTS

The seroprevalence of VZV was 58.1% in the overall population, with a statistically significant correlation between seroprevalence and increasing age (P < 0.0001). A previous history of measles infection (P < 0.04), previous history of varicella infection (P < 0.0001), and the presence of skin lesions (P < 0.05) were significantly associated with seropositivity to VZV.

CONCLUSIONS

Further studies should be performed in order to evaluate the endemicity of VZV infections and to establish criteria for the use of the specific vaccine in Brazil.

Adult psychosis, common childhood infections and neurological soft signs in a national birth cohort

BACKGROUND

Neurological soft signs preceding adult-onset schizophrenia suggest a neurodevelopmental origin and could reflect physical illness in childhood.

AIMS

To investigate possible associations of adult-onset psychosis with neurological soft signs and common infectious illnesses in childhood.

METHOD

Using data from the UK National Child Development Study, a longitudinal general population sample, odds ratios were calculated for clinical diagnoses of common childhood viral illnesses and later adult psychotic illness, childhood epilepsy and a range of neurological soft signs.

RESULTS

The number of illnesses per individual did not relate either to the number of soft signs, or to any particular adult outcome. Schizophrenia, affective psychosis and epilepsy were not associated with common childhood illness but were associated with neurological soft signs and an increased, but small, frequency of previous meningitis and tuberculosis.

CONCLUSIONS

Overall the data support the notion of neurological soft signs as markers of disordered neurodevelopment in schizophrenia (but the early neurological abnormalities are not caused by infectious illness) and an association between meningitis or tuberculosis in childhood and a small proportion of cases of epilepsy, affective psychosis and schizophrenia.

Varicella infection and pneumonia among adults

OBJECTIVES

To demonstrate the clinical importance of adult chickenpox in terms of morbidity, mortality, and impact on hospital services, in Al Ain, United Arab Emirates.

METHODS

A review was conducted of 607 consecutive hospitalized cases of adult chickenpox (1985-1996, Al Ain Hospital) for clinical findings and risk of developing varicella pneumonia.

RESULTS

Leading clinical features were fever (98.9%), myalgia (26.9%), cough (24.6%), headache (15.4%), pharyngitis (14.7%), and profuse rash (12.2%). There were 26 cases of varicella pneumonia, of whom three died with respiratory failure (hospital case fatality 0.5%). Multivariate analysis (odds ratios in parenthesis) showed that cough (12.1), profuse rash (4.5), fever for more than 1 week (3.9), and age over 34 years (2.3) were the most significant predictors of pneumonia.

CONCLUSIONS

Early aggressive therapy with intravenous acyclovir is recommended in patients at risk of pneumonia. In the community setting, there is a large proportion of adult immigrants (especially from South Asia) who are seronegative and at risk of complications and hospitalization. It is recommended that the varicella vaccine be offered to new immigrants after screening, to benefit themselves and the nonexposed community, and to reduce the economic burden of chickenpox on the health services and employers.

Fatal varicella zoster infection in a severe steroid dependent asthmatic patient receiving methotrexate

A case is described of fatal haemorrhagic varicella zoster in a steroid dependent asthmatic patient concurrently receiving methotrexate. The future management of patients on immunosuppressive steroid sparing drugs is discussed.