Additional Epidemiological Information Research Articles

Pros and cons of estimating the reproduction number from early epidemic growth rate of influenza A (H1N1) 2009

BackgroundIn many parts of the world, the exponential growth rate of infections during the initial epidemic phase has been used to make statistical inferences on the reproduction number, R, a summary measure of the transmission potential for the novel influenza A (H1N1) 2009. The growth rate at the initial stage of the epidemic in Japan led to estimates for R in the range 2.0 to 2.6, capturing the intensity of the initial outbreak among school-age children in May 2009.MethodsAn updated estimate of R that takes into account the epidemic data from 29 May to 14 July is provided. An age-structured renewal process is employed to capture the age-dependent transmission dynamics, jointly estimating the reproduction number, the age-dependent susceptibility and the relative contribution of imported cases to secondary transmission. Pitfalls in estimating epidemic growth rates are identified and used for scrutinizing and re-assessing the results of our earlier estimate of R.ResultsMaximum likelihood estimates of R using the data from 29 May to 14 July ranged from 1.21 to 1.35. The next-generation matrix, based on our age-structured model, predicts that only 17.5% of the population will experience infection by the end of the first pandemic wave. Our earlier estimate of R did not fully capture the population-wide epidemic in quantifying the next-generation matrix from the estimated growth rate during the initial stage of the pandemic in Japan.ConclusionsIn order to quantify R from the growth rate of cases, it is essential that the selected model captures the underlying transmission dynamics embedded in the data. Exploring additional epidemiological information will be useful for assessing the temporal dynamics. Although the simple concept of R is more easily grasped by the general public than that of the next-generation matrix, the matrix incorporating detailed information (e.g., age-specificity) is essential for reducing the levels of uncertainty in predictions and for assisting public health policymaking. Model-based prediction and policymaking are best described by sharing fundamental notions of heterogeneous risks of infection and death with non-experts to avoid potential confusion and/or possible misuse of modelling results.

Spatiotemporal dynamics in the early stages of the 2009 A/H1N1 influenza pandemic

Epidemiology and public health planning will increasingly rely on the analysis of genetic sequence data. The ongoing influenza A/H1N1 pandemic may represent a tipping point in this trend, with A/H1N1 being the first human pathogen routinely genotyped from the beginning of its spread. To take full advantage of this genetic information, we introduce a novel method to reconstruct the spatiotemporal dynamics of outbreaks from sequence data. The approach is based on a new paradigm were ancestries are inferred directly rather than through the reconstruction of most recent common ancestors (MRCAs) as in phylogenetics. Using 279 A/H1N1 hemagglutinin (HA) sequences, we confirm the emergence of the 2009 flu pandemic in Mexico. The virus initially spread to the US, and then to the rest of the world with both Mexico and the US acting as the main sources. While compatible with current epidemiological understanding of the 2009 H1N1 pandemic, our results provide a much finer picture of the spatiotemporal dynamics. The results also highlight how much additional epidemiological information can be gathered from genetic monitoring of a disease outbreak.

A survey of 460 supernumerary teeth in Brazilian children and adolescents

This study aimed to survey the demographic profile of supernumerary teeth (ST) in Brazilian children and adolescents. A retrospective analysis was carried out of all nonsyndromic patients with ST attended at the Pediatric Oral Surgery Service of the Universidade Federal de Minas Gerais between 1995 and 2004. Diagnosis of ST was based on clinical and radiographic examination. Chi-squared test was used for statistical analysis. This study included 460 ST found in 305 patients. Radiographic assessment (32.1%) was the main care-seeking reason and also the means through which most (97.6%) permanent ST were identified. Most cases were single (63.0%), conical (44.6%), and unerupted (76.8%) ST. Most teeth were fully developed (41.3%), normally orientated (78.9%), placed in a palatal/lingual-sagittal position (84.1%), adjacent to the crown of permanent teeth (50.2%) (P < 0.001). The most frequent clinical complication was permanent teeth displacement (36.0%). Treatment was surgical removal followed by orthodontics (61.6%). The demographic profile of ST herein presented will be useful to provide additional epidemiological information. A wide range of factors should be considered when evaluating ST. In addition, it is essential to detect ST as early as possible to avoid complications and to assure successful management. Even after treatment, patients must be followed up.

Oral health status of 207 head and neck cancer patients before, during and after radiotherapy

The aim of this retrospective study was to describe the oral health status of patients before, during, and after radiotherapy (RT) for the treatment of head and neck cancer (HNC). Before RT, the following data was collected: presence of unrecoverable teeth, residual roots, unerupted teeth, use of dentures, periodontal alterations, caries, candidiasis, and xerostomia. Mucositis, candidiasis, and xerostomia were evaluated during RT. Patients continued to be followed after RT for evaluation of mucositis, candidiasis, xerostomia, radiation caries, and osteoradionecrosis. For statistical analysis, 95% confidence intervals (CI) were determined using sample size, population, and percentages. Before RT, 120 (57.9%) patients presented with alterations in the oral cavity namely, 85 (41.0%) with periodontal disease, 44 (21.2%) with residual roots, 25 (12.0%) with caries, 15 (7.2%) with candidiasis, and 12 (5.8%) had an unerupted tooth present. Xerostomia was a complaint of 19 patients (9.1%). Restorations were indicated for 33 patients (15.9%), whereas extraction was indicated for 104 (50.2%) patients. During RT, mucositis was found in 80 (61.7%) patients, candidiasis in 60 (45.8%), and xerostomia was a complaint of 82 patients (62.6%). After RT, mucositis persisted in 21 patients (19.2%), candidiasis was identified in 23 patients (21.1%), and xerostomia was reported by 58 patients (53.2%). Radiation caries developed in 12 patients (11.0%), whereas six patients (5.5%) developed osteoradionecrosis. The demographic profile herein presented will be useful as baseline data to provide additional epidemiological information and to determine future measures for prevention and treatment of RT-induced complications and sequelae.

Studies of Multiple Sclerosis in Communities Concerned about Environmental Exposures

Multiple sclerosis (MS) is an autoimmune disease that differentially affects women, people 30-60 years old, and Caucasians. Evidence indicates that it is a complex disease determined by both environmental factors and genetic susceptibility. People across the United States have expressed concern about perceived clusters of MS in their communities and the role of environmental exposures in the development of the disease. The Agency for Toxic Substances and Disease Registry (ATSDR) has funded several studies to address this issue, including a cluster investigation, several prevalence studies, and a case-control study. The cluster investigation illustrated that there are few data regarding the number of individuals with MS in the United States. Prevalence studies were conducted in Ohio, Missouri, and Texas to address this deficiency. The results support a regional difference in MS prevalence, although the reason for this difference is unclear. The results also underscore the need for additional epidemiological information about the distribution of MS in other areas of the United States and information on the underlying etiology of the disease. A case-control study is currently being conducted to examine potential risk factors for MS, including the role of environmental exposures and genetic susceptibility. Future research on MS should focus on large-scale studies and include collaboration among researchers with varied fields of expertise, such as epidemiology, neurology, and genetics.

Identifying Mycobacterium tuberculosis complex strain families using spoligotypes

We present a novel approach for analysis of Mycobacterium tuberculosis complex (MTC) strain genotyping data. Our work presents a first step in an ongoing project dedicated to the development of decision support tools for tuberculosis (TB) epidemiologists exploiting both genotyping and epidemiological data. We focus on spacer oligonucleotide typing (spoligotyping), a genotyping method based on analysis of a direct repeat (DR) locus. We use mixture models to identify strain families of MTC based on their spoligotyping patterns. Our algorithm, SPOTCLUST, incorporates biological information on spoligotype evolution, without attempting to derive the full phylogeny of MTC. We applied our algorithm to 535 different spoligotype patterns identified among 7166 MTC strains isolated between 1996 and 2004 from New York State TB patients. Two models were employed and validated: a 36-component model based on global spoligotype database SpolDB3, and a randomly initialized model (RIM) containing 48 components. Our analysis both confirmed previously expert-defined families of MTC strains and suggested certain new families. SPOTCLUST, which is available online, can be further improved by incorporating data obtained using additional strain genetic markers and epidemiological information. We demonstrate on New York City (NYC) patient data how the resulting models can potentially form the basis of TB control tools using genotyping.

Cognitive processes in music performance anxiety

Music performance anxiety has been investigated either as a discrete phenomenon, or as a variant of social phobia. This study examined the theoretical adequacy of establishing music performance anxiety as a subtype of social phobia, using Rapee and Heimberg's (1997) model of anxiety in social-evaluative situations to account for the cognitions experienced by anxious individuals in solo musical performances. Similarities between the two phenomena in terms of important cognitive processes were revealed in a sample of 84 musicians. The two cognitive constructs in the model deemed to be critical to social phobia were also the only two constructs predicting music performance anxiety. It is concluded that social phobic models may provide a valid account of the cognitive processes occurring in music performance anxiety. These results are combined with additional epidemiological and etiological information in a cognitive conceptualisation of music performance anxiety.

Evaluation of restriction endonuclease fingerprinting of chromosomal DNA and plasmid profile analysis for characterization of multiresistant coagulase-negative staphylococci in bacteremic neonates

A procedure was developed for restriction endonuclease fingerprinting (REF) of the chromosomal DNA of coagulase-negative staphylococci. A total of 48 isolates comprising 29 Staphylococcus epidermidis and 19 Staphylococcus haemolyticus isolates from blood and mucocutaneous sites of 15 premature neonates were characterized by REF, plasmid profile (PP) analysis, antimicrobial susceptibility testing, biotyping, and slime production. On the basis of REF analysis of chromosomal DNA, the 48 coagulase-negative staphylococcal isolates were subdivided into 10 subgroups, whereas PP analysis subdivided the strains into 20 distinct subgroups. REF analysis of total DNA (i.e., chromosome plus plasmid) resulted in the same 20 subgroups as were subdivided by PP analysis. The high discriminatory power of PP analysis was associated with the variability of plasmid content in coagulase-negative staphylococcal strains isolated during the outbreak. REF patterns were found to be stable both in vitro and in vivo. Isolates carried from 2 to 10 plasmids that ranged in molecular size from 0.9 to 39.5 megadaltons. Plasmids were disseminated among the coagulase-negative staphylococci, regardless of the genetic relatedness of their chromosomal DNAs. Hence, a lack of correlation existed between the grouping of isolates by REF analysis of chromosomal DNA and the grouping by PP analysis. There were one and two distinct chromosomal patterns among 4 of 4 blood cultures and 15 of 15 mucocutaneous cultures of S. haemolyticus, respectively. In contrast, a higher proportion of distinct chromosomal patterns was found for S. epidermidis in blood cultures (7 of 11 cultures) compared with those identified for isolates in mucocutaneous cultures (6 of 18 cultures). In summary, REF analysis of chromosomal DNA, rather than total DNA, is a useful marker for epidemiological investigations of coagulase-negative staphylococci. PP analysis can also be used to provide additional epidemiological information regarding the most recent genetic events.

Epidemiology and mechanistic basis of analgesic-associated nephropathy

End-stage renal failure (ESRF) due to analgesic nephropathy is still a common clinical condition in several countries, but the prevalence in dialysis patients shows large geographical differences. The frequency of ESRF of unknown aetiology is the inverse of that linked to analgesic abuse, and data suggest that the occurrence of analgesic nephropathy may be underestimated. The study of analgesic nephropathy is difficult because the earliest damage to the kidney is a renal papillary necrosis (RPN), which cannot easily be diagnosed. Continued analgesic abuse generally leads to a progressive secondary cortical degeneration which is easier to diagnose. If analgesic abuse is stopped at an early enough stage in nephropathy, clinical symptoms stabilize or improve, and ESRF may be averted. A high incidence of upper urothelial carcinoma (UUC) is also observed in individuals with a history of analgesic abuse, but it is still not clear if the two have a related pathogenesis. Study of the mechanism of RPN in animals administered analgesics and nonsteroidal anti-inflammatory drugs (NSAID) has been difficult owing to their extrarenal toxicity. Several model compounds cause identical clinical changes and have as their selective target the renal medullary interstitial cells; subsequently, other changes (including cortical and glomerular degeneration) develop as a secondary cascade. A number of mechanisms have been proposed to explain RPN (e.g., counter-current concentrating mechanism, ischaemic injury, altered prostaglandin metabolism, immunological changes), but peroxidative metabolism of papillotoxic chemicals within the interstitial cells seems to be the most likely cause. Analgesic abuse is a costly socioeconomic condition for which there is currently no clinical treatment. If it is diagnosed early enough, severe renal degeneration can be prevented. Additional epidemiological information is needed to establish the causative role of analgesics and other chemicals, in order to determine the relative risk of each. Additional animal experiments are needed in order to clarify the molecular pathogenesis of RPN and UUC, to differentiate the stages in progression to ESRF and to develop more sensitive and selective diagnostic criteria.

Identification of groups at risk for renal diseases (including nephrotoxicity)

An assessment of the health significance of renal disease due to nephrotoxicity and identification of groups at risk for toxic nephropathy is difficult because the incidence is likely to be underestimated in the available registry data. In more than 50% of all cases of end-stage renal failure, the causality is not known. In end-stage toxic nephropathy, the kidney may show the morphological changes of chronic interstitial nephritis as well as those of chronic glomerulonephritis. Therefore, additional epidemiological data and information on exposure are necessary. Physiological, social and educational factors may aggravate exposure, and the role of multiple exposures is unknown, although individuals at risk are not only those with the highest burden of exposure. Differential sensitivity is explained in part by genetic factors, as shown for abnormal sulphoxidation and slow acetylation. Early identification of groups at risk for nephropathy of clinical significance still relies on the methods of classical nephrology i.e., measurement of proteinuria or decreased glomerular filtration rate, but several new tests are currently under evaluation.