Non-specific colitis among patients with colitis: frequency and relation to inflammatory bowel disease, a prospective study / Colite inespecífica entre pacientes com colite: estudo prospectivo sobre sua frequência e relação com doença inflamatória intestinal

Abstract Background and study aim: The term non-specific colitis refers to an inflammatory condition of the colon that microscopically lacks the characteristic features of any specific form of colitis and is commonly seen in pathology reports of colonoscopy biopsies. In fact, it has been questioned whether it is a separate pathological entity or it is merely an intermediate stage in the course of inflammatory bowel disease. This study was conducted to estimate the prevalence of non-specific colitis among patients with colitis and characterize its natural history over a 6 months year period. Patients and methods: Eighty adult patients presented for colonoscopy were enrolled. In the final analysis they were divided into Group A; the non-specific colitis Group and Group B; the inflammatory bowel disease Group. All patients were subjected to: full history taking, full clinical examination, laboratory investigations: which included stool analysis, CRP, ESR, complete colonoscopy and entire random colon biopsies for histopathological examination. Results: Group A included 67 patients (83.75%) while Group B included 13 (16.25%) patients. Patients with IBD had clinical and laboratory features of inflammation significantly higher than patients with non-specific colitis. Six patients (8.95%) of non-specific colitis group developed histologic features of florid inflammatory bowel disease after 6 months. There were no independent predictors of this conversion. Conclusion: Among our 80 patients with colonoscopy and biopsy 67 (83.75%) were diagnosed as non-specific colitis and out of them 6 patients (8.95%) were reexamined after 6 months and proved to have inflammtory bowel disese this change was not linked to predictive factors.

Resumo Introdução e objetivos: O termo colite inespecífica (CI) refere-se a uma condição inflamatória do cólon que microscopicamente não apresenta características de qualquer forma específica de colite; é comumente observada em relatórios patológicos de biópsias de colonoscopia. De fato, tem-se questionado se esta seria uma entidade patológica separada ou apenas um estágio intermediário no curso da DII. Este estudo foi realizado para estimar a prevalência de CI entre pacientes com colite e caracterizar seu curso durante um período de seis meses. Pacientes e métodos: O estudo incluiu 80 pacientes adultos que se apresentaram para colonoscopia. Na análise, os pacientes foram divididos em dois grupos: grupo A (CI) e grupo B (DII) Todos os pacientes foram submetidos a anamnese completa, exame clínico completo e investigações laboratoriais que incluíram análise de fezes, PCR, VHS, colonoscopia completa e biópsias aleatórias de cólon para exame histopatológico. Resultados: Do total de pacientes, 67 foram alocados no grupo A (83,75%) e 13 (16,25%) no grupo B. Os pacientes com DII apresentavam sinais clínicos e laboratoriais de inflamação significativamente maiores do que o observado em pacientes com CI. Seis pacientes (8,95%) do grupo CI desenvolveram características histológicas de DII florida após seis meses. Não foram identificados preditores independentes para essa conversão. Conclusão: Entre os 80 pacientes submetidos a colonoscopia e biópsia, o diagnóstico de CI foi feito em 67 (83,75%); destes, seis pacientes (8,95%) foram reexaminados após seis meses e apresentaram DII, sendo que essa conversão não foi associada a fatores preditivos.

Colitis microscópica / Microscopic Colitis

El síndrome de colitis microscópica define enfermedades caracterizadas por diarrea crónica, acuosa, de más de cuatro semanas de evolución, acompañadas de otros síntomas digestivos. Generalmente se presenta en pacientes femeninas después de la quinta década de vida, asociada con factores de riesgo como el hábito de fumar, la ingestión de bebidas alcohólicas y el abuso en la ingestión de algunos medicamentos, esta enfermedad también se relaciona en pacientes con enfermedades autoinmunes. En los exámenes se encuentran hallazgos radiológicos y endoscópicos normales en el 80 por ciento de los casos. El diagnóstico se obtiene por medio del estudio histológico de la mucosa del colon. Las enfermedades incluyen colitis colágena y colitis linfocítica. En el presente estudio se realizó una revisión actualizada sobre esta temática que incluyó aspectos epidemiológicos, cuadro clínico, diagnóstico y tratamiento.(AU)

The microscopic colitis syndrome defines diseases characterized by chronic watery diarrhea of more than four weeks of evolution accompanied by other digestive syndromes. It is frequent in female patients of 50 years or more. It is associated with risk factors such as smoking, alcohol and drug intake. This disease is also related to patients suffering from autoimmune disease. In medical examination radiological and endoscopic findings were normal in 80% of the cases. Diagnose is obtained by means of histological studies of de colon mucosa which include collagenous and lymphocytic colitis. In the present study, an updated review was carried out on this topic, which included epidemiological aspects, clinical features, diagnosis and treatment.(AU)

Clostridium difficile colitis in patients undergoing lumbar spine surgery.

STUDY DESIGN: Retrospective database analysis. OBJECTIVE: To investigate incidence, comorbidities, and impact on health care resources of Clostridium difficile infection after lumbar spine surgery. SUMMARY OF BACKGROUND DATA: C. difficile colitis is reportedly increasing in hospitalized patients and can have a negative impact on patient outcomes. No data exist on estimates of C. difficile infection rates and its consequences on patient outcomes and health care resources among patients undergoing lumbar spine surgery. METHODS: The Nationwide Inpatient Sample was examined from 2002 to 2011. Patients were included for study based on International Classification of Diseases, Ninth Revision, Clinical Modification, procedural codes for lumbar spine surgery for degenerative diagnoses. Baseline patient characteristics were determined and multivariable analyses assessed factors associated with increased incidence of C. difficile and risk of mortality. RESULTS: The incidence of C. difficile infection in patients undergoing lumbar spine surgery is 0.11%. At baseline, patients infected with C. difficile were significantly older (65.4 yr vs. 58.9 yr, P<0.0001) and more likely to have diabetes with chronic complications, neurological complications, congestive heart failure, pulmonary disorders, coagulopathy, and renal failure. Lumbar fusion (P=0.0001) and lumbar fusion revision (P=0.0003) were associated with increased odds of postoperative infection. Small hospital size was associated with decreased odds (odds ratio [OR], 0.5; P<0.001), whereas urban hospitals were associated with increased odds (OR, 2.14; P<0.14) of acquiring infection. Uninsured (OR, 1.62; P<0.0001) and patients with Medicaid (OR, 1.33; P<0.0001) were associated with higher odds of acquiring postoperative infection. C. difficile increased hospital length of stay by 8 days (P<0.0001), hospital charges by 2-fold (P<0.0001), and inpatient mortality to 4% from 0.11% (P<0.0001). CONCLUSION: C. difficile infection after lumbar spine surgery carries a 36.4-fold increase in mortality and costs approximately $10,658,646 per year to manage. These data suggest that great care should be taken to avoid C. difficile colitis in patients undergoing lumbar spine surgery because it is associated with longer hospital stays, greater overall costs, and increased inpatient mortality. LEVEL OF EVIDENCE: 3.

[Prevalence of microscopic colitis in patients with irritable bowel syndrome with diarrhea predominance]. / Prevalencia de colitis microscópica en pacientes con criterios del síndrome de intestino irritable con predominio de diarrea.

BACKGROUND: Microscopic colitis (MC) and irritable bowel syndrome with diarrhea (IBSD) have a similar clinical and endoscopic presentation. The prevalence of MC in Mexican patients with IBS-D is unknown. OBJECTIVES: To find out the prevalence of MC in patients with IBS-D and compare it with the one observed in patients with IBS with constipation (IBS-C). METHODS: All patients with IBS (Rome III) seen consecutively from January 2008 to August 2010 were included. Those with organic disease, alarm signs, mixed IBS or unsubtyped- IBS (Rome III) were excluded. Colonoscopy with biopsies was performed in all patients that were examined by two pathologists who did not know the clinical characteristics of the subjects. MC was defined according with the universally accepted histological criteria. RESULTS: 155 patients with IBS-D and 145 with IBS-C were studied. Both groups were matched from the standpoint of age, gender ratio and time course of disease. MC was detected in 28 patients with IBS-D and in one with IBS-C (18% vs. 0.7%, p <0.0001). Fifteen patients with lymphocytic colitis and 14 with collagenous colitis were detected. The endoscopic appearance of the colon mucosa was normal in 20 of the 29 patients with MC (69%). CONCLUSIONS: The prevalence of MC in patients with IBS-D was 18%, significantly higher than the one observed in patients with IBS-C. Colonic mucosa had a normal appearance in most of the patients with MC. Systematic biopsies are recommended in patients with IBS-D.

Prevalence and clinical features of indeterminate colitis in Mexico: a 17-year study.

BACKGROUND: Indeterminate Colitis (IC) is diagnosed after colectomy when macroscopic and microscopic features were not sufficient to allow a definite diagnosis of either the classical types of Ulcerative Colitis (UC) or Crohn's disease (CD). Epidemiological data from some series have reported that IC is diagnosed in between 9% and 20% of colectomy specimens. AIM: To determine the prevalence of IC in Mexican patients and to describe their clinical features. MATERIAL AND METHODS: We carried out a retrospective database analysis of all patients diagnosed with inflammatory bowel disease (IBD) who underwent colectomy between January of 1990 and December of 2006. Demographic data, clinical, laboratory, and histopathological results were analyzed. RESULTS: We found 80 patients in the database who had undergone total colectomy whose average age was 44.8 years. IC was found in 7 patients (8.7%) from colectomy specimens among Mexican patients with IBD, with a mean age at diagnosis of 33.6 years. Subgroup analysis showed that a younger age at diagnosis and toxic megacolon were factors of statistical significance associated with IC. CONCLUSIONS: The prevalence of IC was 8.7% in our group. A younger age of onset and toxic megacolon were the most important associated factors in patients with IC.

Characterization of Shigella spp. by antimicrobial resistance and PCR detection of ipa genes in an infantile population from Porto Velho (Western Amazon region), Brazil.

The incidence of Shigella spp. was assessed in 877 infants from the public hospital in Rondônia (Western Amazon region, Brazil) where Shigella represents the fourth cause of diarrhea. Twenty-five isolates were identified: 18 were Shigella flexneri, three Shigella sonnei, three Shigella boydii and one Shigella dysenteriae. With the exception of S. dysenteriae, all Shigella spp. isolated from children with diarrhea acquired multiple antibiotic resistances. PCR detection of ipa virulence genes and invasion assays of bloody diarrhea and fever (colitis) were compared among 25 patients testing positive for Shigella. The ipaH and ipaBCD genes were detected in almost all isolates and, unsurprisingly, all Shigella isolates associated with colitis were able to invade HeLa cells. This work alerts for multiple antibiotic resistant Shigella in the region and characterizes presence of ipa virulence genes and invasion phenotypesin dysenteric shigellosis.

Characterization of Shigella spp. by antimicrobial resistance and PCR detection of ipa genes in an infantile population from Porto Velho (Western Amazon region), Brazil

The incidence of Shigella spp. was assessed in 877 infants from the public hospital in Rondônia (Western Amazon region, Brazil) where Shigella represents the fourth cause of diarrhea. Twenty-five isolates were identified: 18 were Shigella flexneri, three Shigella sonnei, three Shigella boydii and one Shigella dysenteriae. With the exception of S. dysenteriae, all Shigella spp. isolated from children with diarrhea acquired multiple antibiotic resistances. PCR detection of ipa virulence genes and invasion assays of bloody diarrhea and fever (colitis) were compared among 25 patients testing positive for Shigella. The ipaH and ipaBCD genes were detected in almost all isolates and, unsurprisingly, all Shigella isolates associated with colitis were able to invade HeLa cells. This work alerts for multiple antibiotic resistant Shigella in the region and characterizes presence of ipa virulence genes and invasion phenotypesin dysenteric shigellosis.

Colitis microscópica: valor predictivo de la sospecha clínico-endoscópica en nuestro medio / Microscopic colitis: predictive value of clinical/endoscopical approach

Introducción. El estudio y tratamiento de la diarrea crónica es complejo y de múltiples etapas. En pacientes portadores de diarrea crónica acuosa no sanguinolenta, con estudio normal, se debe considerar la posibilidad de una lesión histológica, aún con aspecto macroscópico normal a la colonoscopía: la Colitis Microscópica (CM). Esta entidad clínico-patológica involucra dos conceptos, la colitis linfocítica (CL), que compromete a la mucosa/submucosa de revestimiento del colon con infiltrado de linfocitos CD8 citotóxicos, o bien la colitis colágena (CC) ,que compromete la membrana basal. Ante la sospecha de CM, obtener biopsias secuenciales en colon derecho e izquierdo para su correcto diagnóstico de acuerdo a patrones histológicos. Objetivos. Conocer la frecuencia de esta entidad clínica en pacientes con diarrea crónica acuosa no sanguinolenta, con colonoscopía y biopsias, y evaluar la relación entre la sospecha clínica y la confirmación histológica. Pacientes y métodos. Se incluyen pacientes estudiados por diarrea crónica acuosa no sanguinolenta en el período enero 2003-febrero 2005, que fueron referidos a colonoscopía. Requisito era estudio completo normal de acuerdo a protocolo de diarrea crónica (leucocitos fecales, estudio malabsorción, intolerancia al glúten, función tiroidea, tolerancia a la lactosa, serología VIH, parasitosis, coprocultivo y cultivos especiales, Toxina A de C. difficile, evaluación psiquiátrica, uso de fármacos, etc). En las íleocolonoscopias se efectuaron biopsias secuenciales colon derecho, izquierdo y recto. El estudio histológico se realizó con Hematoxilina y Eosina, rojo congo, Masón y tricrómico para colágeno. Se excluyeron los pacientes con causa conocida de diarrea crónica o hallazgos de lesión a la colonoscopía. Resultados: De 1.145 colonoscopías, cumplen con los criterios de inclusión 16 pacientes, los que son el objetivo del estudio (1,3 por ciento). Corresponden a 8 varones y 8 mujeres, edad promedio de 60,7 años (47-87). En 10 casos las muestras fueron informadas como Colitis leve (62,5 por ciento); un paciente como colitis moderada (6,25 por ciento) y 4 con alteraciones leves e inespecíficas. Sólo 1 paciente (6,25 por ciento) cumplía con los criterios histológicos exigidos para colitis linfocítica. Conclusiones. La frecuencia en esta serie es inferior a lo referido en la literatura, con un solo caso que cumple con los criterios histológicos de 16 pacientes sospechados.

A consistent pattern of minor immunodeficiency and subtle enteropathy in children with multiple food allergy.

OBJECTIVE: Although immunoglobulin (Ig)E-mediated allergies are readily identifiable, non-IgE-mediated allergies present more diagnostic difficulty. We performed a formal retrospective analysis to determine whether there is a recognizable clinical pattern in children. METHODS: We studied 121 children (mean age, 17.3 months) with multiple food allergies who were recruited on the basis of adequate immunological assessment by using case notes and parental questionnaire. RESULTS: Group 1 (n=44) had rapid reactions to dietary antigens, of whom 41 also showed delayed reactions. Group 2 (n=77) had delayed reactions only. Mean IgE was increased in group 1 but both groups otherwise shared a pattern of increased IgG1, decreased IgG2/4, and low-normal IgA. Lymphocyte subsets were skewed, with an increased percentage of CD4 and CD19 and decreased CD8 and natural killer cells. Gastroesophageal reflux, esophagitis, subtle enteropathy, and constipation were frequent in both groups. Of 55 exclusively breast-fed infants, 44 sensitized before weaning. Twenty-one of the mothers suffered from autoimmunity. CONCLUSIONS: There appears to be a recognizable pattern of immune deviation and minor enteropathy in children with multiple food allergy, irrespective of the speed of reactions. Disturbed gut motility is particularly common, as is a maternal history of autoimmunity.

[Microscopic colitis in patients with chronic diarrhea]. / Colitis microscópica en pacientes con diarrea crónica

It has recently been suggested that there is an association between infectious gastroenteritis and irritable bowel syndrome with chronic diarrhea; and a striking similarity between the microscopic lesion observed in this condition and the lesion described in microscopic colitis (MC). As in developed countries MC is found in only 12.6 to 15% of patients with chronic diarrhea, we thought it worthwhile to investigate in Perú, a developing country with high prevalence of infectious gastroenteritis, the prevalence of MC also in patients with chronic diarrhea. One hundred and ten patients with chronic diarrhea underwent biopsies from the right and left colon, and the biopsies were examined histologically to detect MC of lymphocytic or collagenous type.MC was present in 44 (40%) of the 110 patients with chronic diarrhea, being of lymphocytic type in 42, and of collagenous type in. The prevalence of MC observed in Peruvian patients with chronic diarrhea is high when compared to reports from developed countries. This finding supports the idea that infectious gastroenteritis may, under certain conditions, precipitate the appearance of MC, probably by an autoimmune reaction.

Colitis and colon cancer in cotton-top tamarins (Saguinus oedipus oedipus) living wild in their natural habitat.

The cotton-top tamarin is a nonhuman primate noted for susceptibility to juvenile onset colitis and subsequent colon cancer. About 80% develop colitis in captive environments outside the tropics. The aim was to determine the prevalence of colitis and colorectal cancer in tamarins living wild in their tropical habitat. Endoscopic biopsy was used to compare severity of colitis, inflammatory/immune cell densities, mucosal dysplasia, and occurrence of cancer in wild tamarins in a tropical habitat with tamarins living captive in a temperate climate. Six colon biopsies from each of 69 captives showed severe colitis in 64.5% of biopsies and moderate colitis in 19.5%. Severe colitis was not found in 88 wild tamarins; 13% had moderate colitis. Densities of polymorphonuclear leukocytes, plasma cells, and mononuclear cells in the lamina propria were related directly to the severity of four grades of colitis (normal, mild, moderate, and severe). Histologic or gross signs of carcinoma were detected in 12 captives and low- or high-grade dysplasia in 15. Neither cancer nor dysplasia was found in any of the wild tamarins. The observations suggest that colitis and cancer in the tamarin model are linked to environmental factors.

Escherichia coli O 157:H7-associated hemolytic-uremic syndrome after ingestion of contaminated hamburgers.

We conducted a retrospective analysis of 37 children with Escherichia coli O157:H7-associated hemolytic-uremic syndrome. The infection was traced to contaminated hamburgers at a fast-food restaurant chain. Within 5 days of the first confirmed case, the Washington State Department of Health identified the source and interrupted transmission of infection. Ninety-five percent of the children initially had severe hemorrhagic colitis. Nineteen patients (51%) had significant extrarenal abnormalities, including pancreatitis, colonic necrosis, glucose intolerance, coma, stroke, seizures, myocardial dysfunction, pericardial effusions, adult respiratory disease syndrome, and pleural effusions. Three deaths occurred, each in children with severe multisystem disease. At follow-up two children have significant impairment of renal function (glomerular filtration rate < 80 ml/min/per 1.73 Hm2); both of these children have a normal serum creatinine concentration. Hemolytic-uremic syndrome is the most common cause of acute renal failure in children, and this experience emphasizes the systemic nature of this disease. Clinicians should anticipate that multisystem involvement may occur in these patients, necessitating acute intervention or chronic follow-up. This outbreak of Hemolytic-uremic syndrome also highlights the microbiologic hazards of inadequately prepared food and emphasizes the importance of public health intervention in controlling Hemolytic-uremic syndrome.

[Epidemiology of intestinal infection and operative rehydration strategy at the Mexican Institute of Social Security]. / Epidemiología de la infección intestinal y estrategia operativa de rehidratación en el Instituto Mexicano del Seguro Social.

The purpose of the study was to analyze the trend of morbidity and mortality due to intestinal infections in children under the age of 1 (infants) and 1-4 years old (preschool children) among the population group covered by the Mexican Social Security Institute (IMSS) between 1983 and 1990. For this purpose, information was obtained from death certificates, outpatient consultation reports, and hospital discharges with a diagnosis of intestinal infections. Only direct beneficiaries of the IMSS were included in the study. Total and cause-specific mortality rates for infants and preschool children were calculated, as well as the incidence of intestinal infections in outpatient consultations and hospitalizations and case-fatality rates due to intestinal infections. During the study period, mortality rates among infant and preschool children decreased by 15% and 20%, respectively. A reduction in intestinal infections accounts for 73.2% of the decline in infant mortality and 62.6% of the decrease in mortality of preschool children. Incidence and case-fatality rates of intestinal infections also declined in both age groups. Lower morbidity and mortality rates may be due to the IMSS oral rehydration program and to the fact that most of the population group studied lives in cities and has received basic education. Notwithstanding, obstacles to further reducing the incidence of these diseases still exist.

Colite relacionada à derivação fecal

Uma forma de colite, denominada colite relacionada à derivação fecal, foi observada em segmentos colônicos excluídos do trânsito fecal. O presente estudo prospectivo objetivou identificar e caracterizar esta nova afecção, estabelecer critérios epidemiológicos, endoscópicos e histopatológicos para seu diagnóstico, bem como observar sua evolução após reanastomose colônica. Em 13 pacientes avaliados sem prévia história de doença inflamatória intestinal inespecífica, os aspectos endoscópicos e histológicos desta afecção foram o de um processo inflamatório inespecífico, indistinguível daquele apresentado por colite ulcerativa. Os portadores de colite de derivação eram usualmente oligossintomáticos. Após cirurgia de reconstrução do trânsito intestinal houve regressão das alterações inflamatórias no colo-reto refuncionalizado, o que torna a cirurgia de reanastomose colônica sua forma de tratamento definitivo

A form of colitis named divertion related colitis was observed in segments of excluded colon from the fecal stream by a diverting colostomy. This prospective study aimed to recognize this new pathology and to know its evaluation after the reestablishment of continuity of bowel. We studied 13 patients with no previous history of inflammatory bowel disease. Patients were usually oligossymptomatic. Their endoscopic and histologic features resembled those of active ulcerative colitis. There was resolution once continuity of the colon was reestablished in alI patients

Frequency of identification of cytotoxigenic strains of Escherichia coli in cases of diarrhea from rural and urban communities.

It has been suggested that strains of Escherichia coli producing Vero-Toxin (VTEC) may cause diarrhea or hemorrhagic colitis; however, there are not enough studies to support this hypothesis. We studied the frequency of isolation of VTEC strains in patients with acute diarrhea from rural and urban communities. A total of 1430 strains were analyzed, 361 coming from 118 patients from the rural community (Cadereyta, Qro.) and 1069 from the urban district (D.F.); 95 of these patients were asymptomatic, 213 suffered from watery diarrhea and 43 had bloody diarrhea. For production of toxins, strains were grown in tryptic soy broth for 24h and the culture supernatant was inoculated on HeLa cells; strains were considered cytotoxic when they caused lysis in at least 50% of the cells. In the rural community, VTEC strains were isolated in 20% of the asymptomatics, in 45% of the watery diarrhea patients and in 76% of patients with bloody diarrhea. Frequency of isolation was significantly higher in patients with diarrhea than in asymptomatics (P less than 0.05). The relative risk to present watery diarrhea was 3 and to present bloody diarrhea was 12. In the urban district, VTEC strains were isolated in 13, 7.9 and 4.5% from asymptomatics, watery diarrhea and bloody diarrhea patients, respectively; the relative risk for diarrhea was 1. Colonization by VTEC strains is significantly higher in patients from the rural community and these infected patients have an important risk to develop diarrhea.

Epidemiological aspects of Trichuris and trichuriasis in Caribbean communities.

The review argues for a reappraisal of the health significance of the human whipworm, Trichuris trichiura. Infections with this geohelminth are at least as prevalent as Ascaris lumbricoides in many localities, and are associated with significant morbidity. Infection may result in severe trichuriasis syndrome or, more frequently, in a chronic colitis associated with growth stunting. Under-reporting of the chronic manifestations of disease has resulted in a gross under-estimation of the health impact of trichuriasis. Furthermore, estimation of the population dynamical parameters of T. trichiura transmission suggests that whipworm infections are intrinsically more resistant to control than those of other common geohelminths. A major determinant of the transmission dynamics and morbidity characteristics of this helminthiasis is the aggregation of worm burdens in certain predisposed individuals and age groups. It is suggested that improved understanding of the factors generating this distribution of infection intensity is a pre-requisite for effective control of both infection and morbidity.

Epidemiological aspects of Trichuris and trichuriasis in Caribbean communities

The review argues for a reappraisal of the health significance of the human whipworm, Trichuris trichuria. Infections with this geohelminth are at least as prevalent as Ascaris lumbricoides in many localities, and are associated with significant morbidity. Infection may result in severe trichuriasis syndrome or, more frequently, in a chronic colitis associated with growth stunting. Under-reporting of the chronic manifestations of disease has resulted in a gross under-estimation of the health impact of trichuriasis. Furthermore, estimation of the population dynamical parameters of T. trichiura transmission suggests that whipworm infections are intrinsically more resistant to control than those of other common geohelminths. A major determinant of the transmission dynamics and morbidity characteristics of this helminthiasis is the aggregation of worm burdens in certain predisposed individuals and age groups. It is suggested that improved understanding of the factors generating this distribution of infection intensity is a pre-requisite for effective control of both infection and morbidity.(AU)