Age Distribution Of Cases Research Articles

Linking the incidence and age patterns of clinical malaria to parasite prevalence using a mathematical model

Materials and methods We present an approach to estimating disease incidence from prevalence data accounting for the changing age distribution of cases that occurs as transmission declines. We use a transmission model to capture the shifting agepattern of disease at different transmission intensities through dynamically modelling the acquisition and loss of immunity. The model is fitted to age-stratified data on the incidence of uncomplicated malaria due to Plasmodium falciparum from 24 sites in 9 sub-Saharan African countries. We used Bayesian methods, and accounted for variation in treatment rates and reporting methods (active versus passive case detection).

A Probabilistic Transmission and Population Dynamic Model to Assess Tuberculosis Infection Risk

The purpose of this study was to examine tuberculosis (TB) population dynamics and to assess potential infection risk in Taiwan. A well-established mathematical model of TB transmission built on previous models was adopted to study the potential impact of TB transmission. A probabilistic risk model was also developed to estimate site-specific risks of developing disease soon after recent primary infection, exogenous reinfection, or through endogenous reactivation (latently infected TB) among Taiwan regions. Here, we showed that the proportion of endogenous reactivation (53-67%) was larger than that of exogenous reinfection (32-47%). Our simulations showed that as epidemic reaches a steady state, age distribution of cases would finally shift toward older age groups dominated by latently infected TB cases as a result of endogenous reactivation. A comparison of age-weighted TB incidence data with our model simulation output with 95% credible intervals revealed that the predictions were in an apparent agreement with observed data. The median value of overall basic reproduction number (R₀) in eastern Taiwan ranged from 1.65 to 1.72, whereas northern Taiwan had the lowest R₀ estimate of 1.50. We found that total TB incidences in eastern Taiwan had 25-27% probabilities of total proportion of infected population exceeding 90%, whereas there were 36-66% probabilities having exceeded 20% of total proportion of infected population attributed to latently infected TB. We suggested that our Taiwan-based analysis can be extended to the context of developing countries, where TB remains a substantial cause of elderly morbidity and mortality.

Abstract B89: Multivariate modeling of biological, socioeconomic, and treatment level variables partially explains the differential breast cancer mortality between African Americans and white Americans in Michigan

Abstract Introduction In this study, we examine whether biological, socioeconomic and treatment level factors can explain the observed 2-fold difference in 5-year breast cancer mortality between African Americans (16%) and Whites (8%) in Michigan. We aim to inform the development of robust targets of intervention to reduce this racial disparity. Materials & Methods Our study examines differences in biological factors (stage, grade, estrogen receptor status (ER), progesterone receptor status, socioeconomic factors (insurance type and median income quintile) and treatment level factors (surgery, radiation), as contributors to the racial difference in breast cancer specific mortality. Case data was extracted from the Michigan Cancer Surveillance Program. Subjects diagnosed in 2004 with breast cancer (n=6648) and followed for 5 years, without missing values for key predictor variables were utilized in our analysis. Selecting these specific cases did not greatly alter the racial or age distribution of cases. Results Bivariate analysis showed that African Americans were more than twice as likely to be diagnosed at a metastatic stage than their White counterparts. This was the most prominent predictor variable with an odds ratio (OR) of 60.349 for metastatic cancer relative to in situ disease (p<0.0001). ER negativity (ER−) and PR negativity (PR−) were independent predictors of breast cancer mortality with ORs of 1.694 (p<0.05) and of 1.707, (p<0.05) respectively. African Americans were more likely to be ER− (30.24%) and PR− (42.87%) relative to their White cohorts (ER-20.41%, p<0.05; PR-29.25%, p<0.05). Analysis of insurance type indicated that those who did not have insurance had 1.420 times the odds of dying as those who had private insurance (p<0.05). African Americans had a greater percentage uninsured (18.89%) versus Whites (13.85%, p<0.05). Among treatment variables, receiving surgery was associated with a 73% reduction (p<0.05) in the odds of mortality over not receiving surgery. African Americans were more than twice as likely to not have surgery as their White counterparts (AA: 11.70%, Whites: 4.81%, p<0.05). Finally, receiving radiation therapy was associated with a 14% reduction in the odds of breast cancer associated mortality (p<0.05). African Americans were significantly more likely to not receive radiation therapy than their White cohorts (AA: 66.28% and White: 57.04%, p<0.05). Multivariate analysis indicated that race ceased to be a significant predictor of mortality even after adjusting for biologic, socioeconomic and treatment level variables. The adjusted odds ratio for mortality among African Americans was 1.115 (95% Confidence Interval: 0.848 to 1.466). The unadjusted OR for this variable was 2.11, (p<0.05). Thus, ∼90% of the increased risk for mortality associated with being African American was explained by the predictor variables utilized in our multivariate model. Discussion & Conclusions We determined that race ceases to be an independent predictor of breast cancer mortality when key biological, socioeconomic and treatment level predictor variables are accounted for. Careful examination of the dataset reveals that African Americans are diagnosed at a more advanced stage and grade. Interventions that promote more aggressive breast cancer screening of African Americans would be recommended to increase the likelihood of diagnosis at an earlier stage and grade. However, African Americans also tend to have more aggressive tumor biology reflected in their greater prevalence of ER− and PR− tumors; therefore, part of the racial difference in mortality may be biological. Conversely, socioeconomic factors such as insurance and median income quintile also contributed significantly to the disparity in breast cancer mortality. More African Americans were uninsured, which was an independent predictor of mortality in our adjusted multivariate model. Finally, our analysis showed that surgical and radiation treatments were each associated with lower odds of mortality. African Americans were less likely to either receive surgical or radiation treatment for all stages of breast cancer except metastatic disease. This difference in surgical practice was not due to difference in tumor stage, but rather reflected racial differences in treatment choices. Thus, addressing factors that affect treatment or treatment access for African American patients may be an important target of public health intervention. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B89.

Age distribution of cases and deaths during the 1889 influenza pandemic

Using historical data taken from archival records from five European countries and the United States, we evaluate the age distributions of influenza cases and deaths during the 1889 influenza pandemic. We found that the clinical attack rate in 1889 was relatively high and constant between the ages of 1 and 60 years, but was lower outside of the extremes of this age range. By contrast, age-specific influenza-related mortality rates were J-shaped and increased with age beyond 20 years. We conclude that the age-specific attack rates of the 1889 pandemic were most similar to those of the 1968 pandemic and that influenza-related mortality rates did not follow a W-shaped curve as was observed during the 1918 pandemic. Adding 1889 to the short catalogue of influenza pandemics previously studied makes the 1918 pandemic even more exceptional in terms of mortality burden and age distribution of deaths.

Age Distribution of Cases of 2009 (H1N1) Pandemic Influenza in Comparison with Seasonal Influenza

IntroductionSeveral aspects of the epidemiology of 2009 (H1N1) pandemic influenza have not been accurately determined. We sought to study whether the age distribution of cases differs in comparison with seasonal influenza.MethodsWe searched for official, publicly available data through the internet from different countries worldwide on the age distribution of cases of influenza during the 2009 (H1N1) pandemic influenza period and most recent seasonal influenza periods. Data had to be recorded through the same surveillance system for both compared periods.ResultsFor 2009 pandemic influenza versus recent influenza seasons, in USA, visits for influenza-like illness to sentinel providers were more likely to involve the age groups of 5–24, 25–64 and 0–4 years compared with the reference group of >64 years [odds ratio (OR) (95% confidence interval (CI)): 2.43 (2.39–2.47), 1.66 (1.64–1.69), and 1.51 (1.48–1.54), respectively]. Pediatric deaths were less likely in the age groups of 2–4 and <2 years than the reference group of 5–17 years [OR (95% CI): 0.46 (0.25–0.85) and 0.49 (0.30–0.81), respectively]. In Australia, notifications for laboratory-confirmed influenza were more likely in the age groups of 10–19, 5–9, 20–44, 45–64 and 0–4 years than the reference group of >65 years [OR (95% CI): 7.19 (6.67–7.75), 5.33 (4.90–5.79), 5.04 (4.70–5.41), 3.12 (2.89–3.36) and 1.89 (1.75–2.05), respectively]. In New Zealand, consultations for influenza-like illness by sentinel providers were more likely in the age groups of <1, 1–4, 35–49, 5–19, 20–34 and 50–64 years than the reference group of >65 years [OR (95% CI): 2.38 (1.74–3.26), 1.99 (1.62–2.45), 1.57 (1.30–1.89), 1.57 (1.30–1.88), 1.40 (1.17–1.69) and 1.39 (1.14–1.70), respectively].ConclusionsThe greatest increase in influenza cases during 2009 (H1N1) pandemic influenza period, in comparison with most recent seasonal influenza periods, was seen for school-aged children, adolescents, and younger adults.

Stability of the Age Distribution of Measles Cases Over Time During Outbreaks in Bangladesh, 2004–2006

Despite recommendations from WHO to conduct measles outbreak response vaccination campaigns based on the age distribution of cases at the beginning of an outbreak, few data exist to specifically examine whether the age distribution of cases remains constant over time in a measles outbreak. This analysis explores this question with use of measles outbreak surveillance data from Bangladesh from the period 2004-2006. Pearson χ(2) tests were conducted of age distributions over 2 periods during 41 large laboratory-confirmed measles outbreaks. Statistically significant changes in age distribution over time were observed in 24% of the outbreaks. No single pattern was detected in the shifts in age distribution; however, an increase in the proportion of cases occurring among infants <9 months of age was evident in 6 outbreaks. These findings suggest a need to consider the possibility of a shift in the age distribution over time when planning an outbreak response vaccination campaign.

Spatial and temporal characteristics of the 2009 A/H1N1 influenza pandemic in Peru.

BackgroundHighly refined surveillance data on the 2009 A/H1N1 influenza pandemic are crucial to quantify the spatial and temporal characteristics of the pandemic. There is little information about the spatial-temporal dynamics of pandemic influenza in South America. Here we provide a quantitative description of the age-specific morbidity pandemic patterns across administrative areas of Peru.MethodsWe used daily cases of influenza-like-illness, tests for A/H1N1 influenza virus infections, and laboratory-confirmed A/H1N1 influenza cases reported to the epidemiological surveillance system of Peru's Ministry of Health from May 1 to December 31, 2009. We analyzed the geographic spread of the pandemic waves and their association with the winter school vacation period, demographic factors, and absolute humidity. We also estimated the reproduction number and quantified the association between the winter school vacation period and the age distribution of cases.ResultsThe national pandemic curve revealed a bimodal winter pandemic wave, with the first peak limited to school age children in the Lima metropolitan area, and the second peak more geographically widespread. The reproduction number was estimated at 1.6–2.2 for the Lima metropolitan area and 1.3–1.5 in the rest of Peru. We found a significant association between the timing of the school vacation period and changes in the age distribution of cases, while earlier pandemic onset was correlated with large population size. By contrast there was no association between pandemic dynamics and absolute humidity.ConclusionsOur results indicate substantial spatial variation in pandemic patterns across Peru, with two pandemic waves of varying timing and impact by age and region. Moreover, the Peru data suggest a hierarchical transmission pattern of pandemic influenza A/H1N1 driven by large population centers. The higher reproduction number of the first pandemic wave could be explained by high contact rates among school-age children, the age group most affected during this early wave.

Characterizing the Epidemiology of the 2009 Influenza A/H1N1 Pandemic in Mexico

Mexico's local and national authorities initiated an intense public health response during the early stages of the 2009 A/H1N1 pandemic. In this study we analyzed the epidemiological patterns of the pandemic during April-December 2009 in Mexico and evaluated the impact of nonmedical interventions, school cycles, and demographic factors on influenza transmission. We used influenza surveillance data compiled by the Mexican Institute for Social Security, representing 40% of the population, to study patterns in influenza-like illness (ILIs) hospitalizations, deaths, and case-fatality rate by pandemic wave and geographical region. We also estimated the reproduction number (R) on the basis of the growth rate of daily cases, and used a transmission model to evaluate the effectiveness of mitigation strategies initiated during the spring pandemic wave. A total of 117,626 ILI cases were identified during April-December 2009, of which 30.6% were tested for influenza, and 23.3% were positive for the influenza A/H1N1 pandemic virus. A three-wave pandemic profile was identified, with an initial wave in April-May (Mexico City area), a second wave in June-July (southeastern states), and a geographically widespread third wave in August-December. The median age of laboratory confirmed ILI cases was ∼ 18 years overall and increased to ∼ 31 years during autumn (p<0.0001). The case-fatality ratio among ILI cases was 1.2% overall, and highest (5.5%) among people over 60 years. The regional R estimates were 1.8-2.1, 1.6-1.9, and 1.2-1.3 for the spring, summer, and fall waves, respectively. We estimate that the 18-day period of mandatory school closures and other social distancing measures implemented in the greater Mexico City area was associated with a 29%-37% reduction in influenza transmission in spring 2009. In addition, an increase in R was observed in late May and early June in the southeast states, after mandatory school suspension resumed and before summer vacation started. State-specific fall pandemic waves began 2-5 weeks after school reopened for the fall term, coinciding with an age shift in influenza cases. We documented three spatially heterogeneous waves of the 2009 A/H1N1 pandemic virus in Mexico, which were characterized by a relatively young age distribution of cases. Our study highlights the importance of school cycles on the transmission dynamics of this pandemic influenza strain and suggests that school closure and other mitigation measures could be useful to mitigate future influenza pandemics. Please see later in the article for the Editors' Summary.

Influence of birth rates and transmission rates on the global seasonality of rotavirus incidence

Rotavirus is a major cause of mortality in developing countries, and yet the dynamics of rotavirus in such settings are poorly understood. Rotavirus is typically less seasonal in the tropics, although recent observational studies have challenged the universality of this pattern. While numerous studies have examined the association between environmental factors and rotavirus incidence, here we explore the role of intrinsic factors. By fitting a mathematical model of rotavirus transmission dynamics to published age distributions of cases from 15 countries, we obtain estimates of local transmission rates. Model-predicted patterns of seasonal incidence based solely on differences in birth rates and transmission rates are significantly correlated with those observed (Spearman's ρ = 0.65, p < 0.05). We then examine seasonal patterns of rotavirus predicted across a range of different birth rates and transmission rates and explore how vaccination may impact these patterns. Our results suggest that the relative lack of rotavirus seasonality observed in many tropical countries may be due to the high birth rates and transmission rates typical of developing countries rather than being driven primarily by environmental conditions. While vaccination is expected to decrease the overall burden of disease, it may increase the degree of seasonal variation in the incidence of rotavirus in some settings.

Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity

Please cite this paper as: Jhung et al. (2011) Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity. Influenza and Other Respiratory Viruses 5(5), 321–327. Background To augment established influenza surveillance systems in the United States, the Centers for Disease Control and Prevention and the Council of State and Territorial Epidemiologists implemented the Aggregate Hospitalization and Death Reporting Activity (AHDRA) in August 2009. The AHDRA was designed to meet increased demands for timely and detailed information describing illness severity during the 2009 H1N1 influenza A (pH1N1) pandemic response. Objectives We describe the implementation of AHDRA and provide preliminary results from this new surveillance activity. Methods All 50 US states were asked to report influenza‐associated hospitalizations and deaths to AHDRA each week using either a laboratory‐confirmed or syndromic surveillance definition. Aggregate counts were used to calculate age‐specific weekly and cumulative rates per 100 000, and laboratory‐confirmed reports were used to estimate the age distribution of pH1N1 influenza‐associated hospitalizations and deaths. Results From August 30, 2009, through April 6, 2010, AHDRA identified 41 689 laboratory‐confirmed influenza‐associated hospitalizations and 2096 laboratory‐confirmed influenza‐associated deaths. Aggregate Hospitalization and Death Reporting Activity rates peaked earlier than hospitalization and death rates seen in previous influenza seasons with other surveillance systems, and the age distribution of cases revealed a tendency for hospitalizations and deaths to occur in persons <65 years for age. Conclusions Aggregate Hospitalization and Death Reporting Activity laboratory‐confirmed reports provided important information during the 2009 pandemic response. Aggregate Hospitalization and Death Reporting Activity syndromic reports were marked by low representativeness and specificity and were therefore less useful. The AHDRA was implemented quickly and may be a useful surveillance system to monitor severe illness during future influenza pandemics.

Recurring Measles Epidemic in Vietnam 2005-2009: Implication for Strengthened Control Strategies

Measles remains a serious vaccine preventable cause of mortality in developing nations. Vietnam is aiming to achieve the level of immunity required to eliminate measles by maintaining a high coverage of routine first vaccinations in infants, routine second vaccinations at school entry and supplementary local campaigns in high-risk areas. Regular outbreaks of measles are reported, during 2005-2009. National measles case-based surveillance data collected during 2005-June 2009 was analyzed to assess the epidemiological trend and risk factors associated with measles outbreak in Vietnam. Of the 36,282 measles suspected cases reported nationwide, only 7,086 cases were confirmed through laboratory examination. Although cyclical outbreaks occurred between 2005 and 2009, there was no definite trend in measles outbreaks during these periods. Overall, 2438 of measles confirmed cases were among children ≤5 years and 3068 cases were among people ≥16 years. The distribution with respect to gender skewed towards male (3667 cases) significant difference was not observed (P= 0.1693). Unsurprisingly, 4493 of the confirmed cases had no history of vaccination (X(2) <0.01). The northern and highland regions were identified as the main endemic foci and the spatial distribution changed with time. The occurrence of cases, in a considerable proportion of vaccinated population, is not only a reflection of the high vaccination coverage in Vietnam but also portrays a possibility of less than 100% vaccine efficacy. More so, in order to prevent measles in adults, high-risk groups must be identified and catch-up for selected groups selected. This study therefore reinforces the need for continued improvement of surveillance system and to probe into the possible role of changes in age-distribution of cases if the effective control of measles is to be achieved.

Pandemic mitigation: Bringing it home

In the US, national, regional and even institutional plans for ameliorating the effects of pandemic influenza focus on stockpiling antiviral medications, early production and distribution of vaccine, mass and personal social distancing, and a number of personal hygiene activities. Essential personnel are the first scheduled to receive preventive and therapeutic pharmaceuticals, followed by high risk groups, the largest of which are the elderly. Specific recommendations for protection embody a bunker mentality with a time horizon of two weeks, emulating preparation for a natural disaster. The epidemiology of pandemic influenza is scarcely considered. We summarize here the envelope of mortality attributable to epidemic and pandemic influenza in the last 90 years of the last century as a lead in to a presentation of the multinational case age distribution of the novel H1N1 pandemic of 2009. We discuss the sparing of elderly subpopulations in pandemics and the subsequent abrupt resurgence of mortality in the spared age groups as drift variants emerge. The general decline in the baseline of age-specific excess mortality in economically developed countries is characterized and its importance assessed. Models of acute and chronic care facilities are discussed and an argument is advanced that society as a whole as well as acute care facilities cannot be protected against incursion and widespread infection in pandemics of severity above low moderate. The key findings of models of chronic care institutions and others that can control public access, such as corporations, are used to describe programs with a realistic chance of providing protection in even severe pandemics. These principles are further mapped onto individual residences. Materials directing institutional and home planning are cited.

Measles outbreak in Tanzania, 2006–2007

We conducted a measles outbreak investigation in Dar es Salaam, Tanzania. Surveillance data were analyzed; a susceptibility profile developed, and case–control study conducted. The age distribution of cases peaked among those <2, 5–7, and ≥18 years, corresponding to the age distribution of susceptibles. Risk factors included being unvaccinated (aOR = 5.7, p < 0.01) or having received one dose of vaccine compared to two (aOR = 2.4, p = 0.01), being younger, and having a less-educated caretaker. Vaccine effectiveness was 88% (one dose) and 96% (two doses). Results highlight the importance of receiving one dose of measles vaccine, and the added benefit of two doses.

Impact of the routine varicella vaccination programme on varicella epidemiology in Germany

Routine varicella vaccination with one dose for children of 11 to 14 months was recommended in Germany in 2004 to reduce disease incidence and severe complications. A country-wide varicella sentinel surveillance system was initiated in 2005 to detect trends of disease frequency and vaccine uptake and to evaluate the vaccination programme. A convenient sample of about 1,000 paediatricians and general practitioners was recruited to report on a monthly basis on varicella cases by age groups seen in their practice, and on varicella vaccine doses administered. Sentinel data from April 2005 to March 2009 show a reduction of 55% of varicella cases in all ages; 63% in the age group 0-4 years and 38% in 5-9-year-olds. The number of vaccine doses per reporting unit in all regions and physician groups increased during the same period. The number of reported cases as well as administered vaccines differed between physician groups and regions with different reimbursement policies. Where reimbursement was settled early and vaccine doses were increasing varicella cases started to decrease early as well. Besides reimbursement policies the availability and vaccination schedules influenced vaccine uptake. Sentinel surveillance provided valid data on trends for varicella associated morbidity, vaccine uptake and the age distribution of cases. The results confirm that following the introduction of routine varicella vaccination, varicella morbidity started to decline in Germany.

Does Glycosylation as a modifier of Original Antigenic Sin explain the case age distribution and unusual toxicity in pandemic novel H1N1 influenza?

BackgroundA pandemic novel H1N1 swine-origin influenza virus has emerged. Most recently the World Health Organization has announced that in a country-dependent fashion, up to 15% of cases may require hospitalization, often including respiratory support. It is now clear that healthy children and young adults are disproportionately affected, most unusually among those with severe respiratory disease without underlying conditions. One possible explanation for this case age distribution is the doctrine of Original Antigenic Sin, i.e., novel H1N1 may be antigenically similar to H1N1 viruses that circulated at an earlier time. Persons whose first exposure to influenza viruses was to such similar viruses would be relatively immune. However, this principle is not sufficient to explain the graded susceptibility between ages 20 and 60, the reduced susceptibility in children below age 10, and the unusual toxicity observed.MethodsWe collected case data from 11 countries, about 60% of all cases reported through mid-July 2009. We compared sequence data for the hemagglutinin of novel H1N1 with sequences of H1N1 viruses from 1918 to the present. We searched for sequence differences that imply loss of antigenicity either directly through amino acid substitution or by the appearance of sites for potential glycosylation proximal to sites known to be antigenic in humans. We also considered T-cell epitopes.ResultsIn our composite, over 75% of confirmed cases of novel H1N1 occurred in persons ≤ 30 years old, with peak incidence in the age range 10-19 years. Less than 3% of cases occurred in persons over 65, with a gradation in incidence between ages 20 and 60 years.The sequence data indicates that novel H1N1 is most similar to H1N1 viruses that circulated before 1943. Novel H1N1 lacks glycosylation sites on the globular head of hemagglutinin (HA1) near antigenic regions, a pattern shared with the 1918 pandemic strain and H1N1 viruses that circulated until the early 1940s. Later H1N1 viruses progressively added new glycosylation sites likely to shield antigenic epitopes, while T-cell epitopes were relatively unchanged.ConclusionsIn this evolutionary context, Original Antigenic Sin exposure should produce an immune response increasingly mismatched to novel H1N1 in progressively younger persons. We suggest that it is this mismatch that produces both the gradation in susceptibility and the unusual toxicity. Several murine studies suggest specific cell types as a likely basis of the unusual toxicity. These studies also point to widely available pharmaceutical agents as plausible candidates for mitigating the toxic effects. The principle of Original Antigenic Sin modified by glycosylation appears to explain both the case age distribution and the unusual toxicity pattern of the novel H1N1 pandemic. In addition, it suggests pharmaceutical agents for immediate investigation for mitigation potential, and provides strategic guidance for the distribution of pandemic mitigation resources of all types.

DO INTRACRANIAL NEOPLASMS DIFFER IN OLLIER DISEASE AND MAFFUCCI SYNDROME? AN IN-DEPTH ANALYSIS OF THE LITERATURE

Ollier disease (OD) and Maffucci syndrome are closely related, very rare syndromes, that are both associated with multiple sites of chondrodysplasia. They differ primarily with the additional association of Maffucci syndrome with vascular abnormalities, including hemangiomas. Both are associated with chondrosarcomas and other nonsarcomatous neoplasms (NSN), but Maffucci syndrome is thought to have greater malignancy potential. We examined whether OD and Maffucci syndrome differ in the number, histology, in the location of intracranial malignancies, and in the demographics of such patients, as reported in the medical literature. Relevant cases were identified by electronic searches on PubMed, SciSearch, Scientific Commons, Springer Link, and Google. Translate DotNet and Babelfish were used to translate non-English text. Unpaired Student's t tests were used to compare OD and Maffucci syndrome, and chondrosarcoma and NSN patients for mean age; Pearson chi analysis was used for comparisons of gender distribution, geographical distribution (by continent), site of lesion, and for OD versus Maffucci syndrome, tumor type (chondrosarcoma versus NSN). Forty-six patients with 47 intracranial malignancies were identified: 24 with OD, including 6 with a chondrosarcoma and 18 with an NSN; and 22 with Maffucci syndrome, including 13 with a chondrosarcoma, 8 with an NSN, and 1 with both. The 2 syndromes were statistically different in the distribution of chondrosarcomas versus NSNs (P = 0.002). All chondrosarcomas originated at the base of the cranium. All 18 NSNs in OD were of glial cell origin, but only 5 of 9 NSNs in Maffucci syndrome were glial; other tumors included pituitary adenoma, olfactory neuroblastoma, malignant chordoma, and spindle cell hemangioendothelioma. Patients with OD were more than 10 years younger than their Maffucci syndrome counterparts (24.7 versus 34.9 years; P = 0.002), as were patients with OD and chondrosarcoma versus those with Maffucci syndrome and chondrosarcoma (24.7 versus 36.2 years; P = 0.035). The 2 syndromes did not differ in overall sex distribution. OD and Maffucci syndrome differed in geographical distribution, with 10 Maffucci syndrome but no OD patients with malignancy either in Asia (7 patients) or South America (3 patients). Among NSNs, OD and Maffucci syndrome did not differ as to site of lesion within the brain. OD and Maffucci syndrome differ with respect to the distribution of intracranial malignancies by histology, and geographical and age distribution of cases, with OD patients younger by approximately a decade, and Maffucci syndrome patients more likely to live in Asia or South America.

Assessing the Effectiveness and Public Health Impact of Rotavirus Vaccines after Introduction in Immunization Programs

Two new vaccines against severe rotavirus gastroenteritis that have high efficacy in middle- and high-income countries have recently been licensed in many countries worldwide. Clinical trials in low-income countries in Africa and Asia are ongoing. Experience gained through studies of natural rotavirus infection and the clinical trials for the current and previous rotavirus vaccines indicate that, as countries begin to introduce these newly approved vaccines into routine childhood immunization programs, monitoring their performance in real world settings should be a high priority. Key epidemiological considerations in the postlicensure period include (1) how the vaccine will perform against severe rotavirus disease under routine public health use; (2) how routine vaccination will impact the epidemiology of disease with regard to the burden of severe disease and death, age distribution of cases, seasonality, and serotype distribution; (3) whether vaccination will have a sufficient impact on transmission to reduce disease burden in unvaccinated age groups; and (4) whether vaccine will confer protection through the first 3 years of life, when most severe disease and mortality associated with rotavirus occur. Monitoring of impact with focus on these public health considerations will allow parents, health care providers, and decision makers to appreciate the health benefits of vaccination in reducing the burden of severe rotavirus disease. It will also allow assessment of the effectiveness of rotavirus vaccines in programmatic use and the need for modifying vaccination schedules or vaccine formulations to enhance the performance of immunization. In this article, we review data for the protective efficacy of the 2 new rotavirus vaccines, with emphasis on issues particularly important for consideration as these vaccines are introduced in routine infant immunization programs.

The Impact of the Demographic Transition on Dengue in Thailand: Insights from a Statistical Analysis and Mathematical Modeling

An increase in the average age of dengue hemorrhagic fever (DHF) cases has been reported in Thailand. The cause of this increase is not known. Possible explanations include a reduction in transmission due to declining mosquito populations, declining contact between human and mosquito, and changes in reporting. We propose that a demographic shift toward lower birth and death rates has reduced dengue transmission and lengthened the interval between large epidemics. Using data from each of the 72 provinces of Thailand, we looked for associations between force of infection (a measure of hazard, defined as the rate per capita at which susceptible individuals become infected) and demographic and climactic variables. We estimated the force of infection from the age distribution of cases from 1985 to 2005. We find that the force of infection has declined by 2% each year since a peak in the late 1970s and early 1980s. Contrary to recent findings suggesting that the incidence of DHF has increased in Thailand, we find a small but statistically significant decline in DHF incidence since 1985 in a majority of provinces. The strongest predictor of the change in force of infection and the mean force of infection is the median age of the population. Using mathematical simulations of dengue transmission we show that a reduced birth rate and a shift in the population's age structure can explain the shift in the age distribution of cases, reduction of the force of infection, and increase in the periodicity of multiannual oscillations of DHF incidence in the absence of other changes. Lower birth and death rates decrease the flow of susceptible individuals into the population and increase the longevity of immune individuals. The increase in the proportion of the population that is immune increases the likelihood that an infectious mosquito will feed on an immune individual, reducing the force of infection. Though the force of infection has decreased by half, we find that the critical vaccination fraction has not changed significantly, declining from an average of 85% to 80%. Clinical guidelines should consider the impact of continued increases in the age of dengue cases in Thailand. Countries in the region lagging behind Thailand in the demographic transition may experience the same increase as their population ages. The impact of demographic changes on the force of infection has been hypothesized for other diseases, but, to our knowledge, this is the first observation of this phenomenon. Please see later in the article for the Editors' Summary.

Episodic outbreaks bias estimates of age-specific force of infection: a corrected method using measles as an example

Understanding age-specific differences in infection rates can be important in predicting the magnitude of and mortality in outbreaks and targeting age groups for vaccination programmes. Standard methods to estimate age-specific rates assume that the age-specific force of infection is constant in time. However, this assumption may easily be violated in the face of a highly variable outbreak history, as recently observed for acute immunizing infections like measles, in strongly seasonal settings. Here we investigate the biases that result from ignoring such fluctuations in incidence and present a correction based on the epidemic history. We apply the method to data from a measles outbreak in Niamey, Niger and show that, despite a bimodal age distribution of cases, the estimated age-specific force of infection is unimodal and concentrated in young children (<5 years) consistent with previous analyses of age-specific rates in the region.

A Review Of In-Hospital Surgical Mortality At The Nnamdi Azikiwe University Teaching Hospital Nnewi, Nigeria

Aims and Objectives: A retrospective study to determine In-hospital surgical mortality rate, gender and age distribution of cases and operations associated with In-hospital surgical mortality at the Nnamdi Azikiwe University Teaching Hospital, Nnewi. Patients and Methods: Data was collected from the theatre operation registers, ward registers and case notes of all patients who were admitted into the surgical wards including those who died within 30 days of admission. From the 1st of January 2000 to 31st December 2003. Results: Two thousand, Nine hundred and ninety two (2,992) patients were admitted into the surgical wards under the care of surgeons within the period of study and there were 249 deaths giving an In-hospital surgical mortality rate of 8.3%. Only 124 cases notes could be retrieved from the records dept. (50%). Ninety-seven (78.2%) of these patients were males and 27(21.8%) were females giving a (male: female ratio of 3.6:1). The age of the patients ranged from less than 1yr to 95yrs. Forty three (34.7%) patients were operated upon while 81 (65.35) patients did not have any form of operative intervention because the patients presented late and were in poor clinical states. The ratio of those who were operated upon to those who were not operated upon was 1:1.9. Conclusion: In-hospital surgical mortality of 8.3% in our centre is the same as that for low volume hospitals (LVHS) in developed countries. Also, from this study, In-hospital surgical mortality was not operation related since more deaths occurred in patients who were not operated because of late presentation, hence aggressive enlightenment campaigns aimed at encouraging people to report early to hospital may help to reduce the rate of In-hospital surgical mortality in our centre. Keywords: In-hospital, surgical mortality, operation related.Tropical Journal of Medical Research Vol. 11 (2) 2007: pp. 26-30