A field reciprocal transplant experiment reveals asymmetric costs of migration between lake and river ecotypes of three-spined sticklebacks (Gasterosteus aculeatus).

Theory of local adaptation predicts that nonadapted migrants will suffer increased costs compared to local residents. Ultimately this process can result in the reduction of gene flow and culminate in speciation. Here, we experimentally investigated the relative fitness of migrants in foreign habitats, focusing on diverging lake and river ecotypes of three-spined sticklebacks. A reciprocal transplant experiment performed in the field revealed asymmetric costs of migration: whereas mortality of river fish was increased under lake conditions, lake migrants suffered from reduced growth relative to river residents. Selection against migrants thus involved different traits in each habitat but generally contributed to bidirectional reduction in gene flow. Focusing particularly on the parasitic environments, migrant fish differed from resident fish in the parasite community they harboured. This pattern correlated with both cellular phenotypes of innate immunity as well as with allelic variation at the genes of the major histocompatibility complex. In addition to showing the costs of migration in three-spined sticklebacks, this study highlights the role of asymmetric selection particularly from parasitism in genotype sorting and in the emergence of local adaptation.

Hiponatremia e hipofosforemia en las neumonías: ¿qué papel desempeña el riñón? / Hyponatremia and hypophosphatemia in pneumonia: what role does the kidney?

Antecedentes: La hiponatremia es una alteración electrolítica relativamente frecuente en pacientes con neumonía, cuya patogenia se relaciona con el síndrome de secreción inapropiada de hormona antidiurética. El objetivo de este estudio era describir las alteraciones hidroelectrolíticas y hormonales en niños, previamente sanos, diagnosticados de neumonía adquirida en la comunidad (NAC), y compararlas con las de los niños sanos. Material y métodos: Se llevó a cabo un estudio de casos y controles. El grupo de casos (n= 25) estuvo formado por pacientes diagnosticados de NAC según criterios de la Organización Mundial de la Salud, con una media de edad de 4,2 ± 2,4 años; ninguno había recibido fluidoterapia intravenosa. En el grupo control (n= 27) se incluyeron niños sanos, con una media de edad de 5 ± 2,6 años, autorizados a participar en el estudio. Se realizó un análisis bioquímico en sangre y en orina (en micción aislada). En el grupo de NAC se determinaron las cifras de proteína C reactiva (PCR), procalcitonina (PCT) y vasopresina (ADH). Resultados: Los valores medios séricos del sodio, aunque en rango normal, fueron significativamente menores en el grupo de casos que en el grupo control, al igual que la excreción fraccional de sodio (EFNa), cuyo valor medio fue significativamente menor que el del grupo control. No hubo relación entre la natremia, la EFNa y los niveles de ADH. Se encontró una relación significativamente negativa entre los valores de sodio y la temperatura axilar (r= -0,64; p <0,001), la PCR (r= -0,41; p <0,04) y el recuento de leucocitos (r= -0,43; p <0,01) en sangre periférica. El valor medio del fósforo sérico era significativamente inferior al del grupo control. Se encontró una relación significativa entre la fosforemia y la reabsorción tubular de fosfato, expresada mediante TP/GFR (r= 0,97; p <0,001), y la PCR (r= -0,4; p <0,04). Conclusiones: En esta serie, los pacientes con NAC muestran una clara tendencia a presentar un descenso de la natremia. Esta tendencia es de causa extrarrenal y se relaciona significativamente con el proceso inflamatorio secundario a la infección. El descenso del fósforo sanguíneo también se relaciona con la infección, y es secundaria a una pérdida excesiva de fósforo por el riñón (AU)

Introduction: Hyponatremia is a relatively common electrolyte disturbance in patients with pneumonia and its pathogenesis has been related with the syndrome of inappropriate secretion of antidiuretic hormone. The aim of this study was to describe the electrolyte and hormonal abnormalities in children diagnosed with community-acquired pneumonia (CAP) and compare them with those obtained in healthy children. Material and methods: This is a case-control study. In the case group we included patients with CAP (n= 25), according to WHO criteria. None of the patients has received intravenous fluids. The control group (n= 27) included healthy children without disease. Biochemical blood and urine (isolated urination) were determined as analytical tests. In the CAP group C-reactive protein (CRP), procalcitonin (PCT) and levels of vasopressin (ADH) were determined. Results: The serum sodium mean values and the fractional excretion of sodium (FENa) were significantly lower in the case group than in the control group, although they were both in the normal range. There was no relationship between serum sodium, FENa and ADH levels. A significantly negative relationship was found between sodium and axillary temperature (r= -0.64; p <0.001), CRP (r= -0.41; p <0.04) and the leukocyte count in peripheral blood (r= -0.43; p <0.01). The mean serum phosphorus level was significantly lower in the case group. A remarkable relationship between phosphoremia and tubular phosphate reabsorption, expressed by TP/GFR (r= 0.97; p <0.001), and CRP (r= -0.4; p <0.04) was found. Conclusions: In this series, cases with CAP show a clear tendency of decreased serum sodium. This trend has an extrarenal cause and it is significantly related to the inflammatory process secondary to the infection. Hypophosphoremia also relates to infection and is secondary to excessive loss of phosphorus by the kidney (AU)

Duplicaciones del tracto urinario / Urinary tract duplication

Objetivos: Revisar las características clínicas y radiológicas de las distintas formas de duplicación del tracto urinario, valorando la evolución de los casos y la incidencia de lesión en el parénquima renal. Material y métodos: Se estudió retrospectivamente a 301 niños diagnosticados de duplicación pieloureteral mediante ecografía urológica, cistografía miccional seriada (CUMS) y gammagrafía renal con tecnecio99 (DMSA). Resultados: Se clasificaron en 4 grupos. El primer grupo estaba constituido por 166 (55,1%) casos, que presentaban una duplicación pieloureteral completa sin componente obstructivo (DC). Los que presentaban una obstrucción del sistema superior, bien por presentar un uréter ectópico (UE) 19 (6,3%) o un ureterocele (UTC) 35 (11,6%) se dividieron en 2 grupos distintos. El cuarto grupo 81 (26,9%) presentaban una duplicación pieloureteral incompleta (DI). El estudio nefrourológico se realizó en 181/301 tras presentar una infección del tracto urinario; en 100/301 tras detectarse prenatalmente una hidronefrosis. En 20/301 el diagnóstico fue casual. El porcentaje de ecografías al diagnóstico con dilatación del hemirriñón superior fue significativamente superior en los UE 16/19 (84%) y en los UTC 33/35 (94%), en relación con las dilataciones del polo superior encontradas en DC 35/166 (21%) y DI 21/81 (25%).Fueron intervenidos quirúrgicamente 69/166 (41%) de las DC; 7/81 (9%) de las DI; 16/19 (84%) de los UE, y 34/35 (97%) de los UTC. Tres casos con UE y 8 con UTC requirieron una segunda intervención y 3 fueron sometidos a una tercera intervención. El 58% de los pacientes pertenecientes al grupo de DC, 87% de las DI, 29% de los UE, 5% de los UTC, no mostraron alteraciones gammagráficas. Al estudiar las duplicaciones renales no intervenidas se observa que había 98 unidades refluyentes en las DC y de 74 en las DI. La tasa de resolución espontánea de los RVU fue del 80% en la DC y del 90% en la DI (prueba de McNemar p<0,001). El tiempo medio de curación osciló entre 1 año y 5 años (media de 3 años y 3 meses). Conclusión: Los pacientes con más riesgo de presentar lesión renal son los que presentaban una duplicación con obstrucción del hemirriñón superior por inserción ectópica del uréter y especialmente por ureterocele (AU)

Objectives: Review the clinical and radiological characteristics of the different kinds of urinary tract duplications, assessing the outcome of the cases and the incidence of renal parenchymal injury. Material and methods: A retrospective study was performed including 301 children diagnosed of renal duplication by urological ultrasound, voiding cystourethrogram (VCUG) and 99-technetium renal scintigraphy (DMSA). Results: They were classified in four groups. The first consisted of 166 (55.1%) cases that had complete ureteral duplication without an obstructive component (CD). The cases that had an upper system obstruction due to an ectopic ureter (EU), 19 (6.3%), or an ureterocele (UTC), 35 (11.6%), were divided into two different groups. The fourth group 81 (26.9%) had incomplete ureteral duplication. The nephro-urological study was performed in 181/301 after a urinary tract infection; in 100/301 after a prenatal finding of hydronephrosis. It was a casual diagnosis in 20/301.The percentage upper kidney dilation in the diagnostic ultrasound was significantly higher in those with EU 16/19 (84%) and in those with UTC 33/35 (94%), compared with the upper pole dilations found in the CD 35/166 (21%) and ID 21/81 (25%).Surgery was performed in 96/166 (41%) of the CD, 7/81 of the ID, 16/19 (84%) of the EU, and 34/35 (97%) of the UTC. Three cases with EU and 8 with UTC needed a second surgery, and 3 a third one. No scintigraphy changes were observed in 58% of the patients in the CD group, 87% in the ID group, 29% in the EU group, and 5% in the UTC group. As regards the renal duplications who did not have surgery, it was found that there were 98 refluxing units in the CD, and 74 in the ID. The spontaneous resolution of the vesicoureteral reflux (VUR) was 80% in the CD, and 90% in the ID (McNemar test P<0.001). The average healing time ranged from 1 year to 5 years (Mean: 3 years and 3 months). Conclusion: The patients with higher risk of having renal injury are those who presented with a duplication with upper kidney obstruction due to ectopic insertion of the ureter, particularly due to an ureterocele (AU)

[Urinary tract duplication]. / Duplicaciones del tracto urinario.

OBJECTIVES: Review the clinical and radiological characteristics of the different kinds of urinary tract duplications, assessing the outcome of the cases and the incidence of renal parenchymal injury. MATERIAL AND METHODS: A retrospective study was performed including 301 children diagnosed of renal duplication by urological ultrasound, voiding cystourethrogram (VCUG) and 99-technetium renal scintigraphy (DMSA). RESULTS: They were classified in four groups. The first consisted of 166 (55.1%) cases that had complete ureteral duplication without an obstructive component (CD). The cases that had an upper system obstruction due to an ectopic ureter (EU), 19 (6.3%), or an ureterocele (UTC), 35 (11.6%), were divided into two different groups. The fourth group 81 (26.9%) had incomplete ureteral duplication. The nephro-urological study was performed in 181/301 after a urinary tract infection; in 100/301 after a prenatal finding of hydronephrosis. It was a casual diagnosis in 20/301. The percentage upper kidney dilation in the diagnostic ultrasound was significantly higher in those with EU 16/19 (84%) and in those with UTC 33/35 (94%), compared with the upper pole dilations found in the CD 35/166 (21%) and ID 21/81 (25%). Surgery was performed in 96/166 (41%) of the CD, 7/81 of the ID, 16/19 (84%) of the EU, and 34/35 (97%) of the UTC. Three cases with EU and 8 with UTC needed a second surgery, and 3 a third one. No scintigraphy changes were observed in 58% of the patients in the CD group, 87% in the ID group, 29% in the EU group, and 5% in the UTC group. As regards the renal duplications who did not have surgery, it was found that there were 98 refluxing units in the CD, and 74 in the ID. The spontaneous resolution of the vesicoureteral reflux (VUR) was 80% in the CD, and 90% in the ID (McNemar test P<.001). The average healing time ranged from 1 year to 5 years (Mean: 3 years and 3 months). CONCLUSION: The patients with higher risk of having renal injury are those who presented with a duplication with upper kidney obstruction due to ectopic insertion of the ureter, particularly due to an ureterocele.

Major histocompatibility complex polymorphism: dynamics and consequences of parasite-mediated local adaptation in fishes.

Parasitism is a common form of life and represents a strong selective pressure for host organisms. In response to this evolutionary pressure, vertebrates have developed genetically coded defences such as the major histocompatibility complex (MHC). Mechanisms of parasite-mediated selection not only maintain outstanding polymorphism in these genes but have also been proposed to further promote host population divergence and ultimately speciation because it can drive evolution of local adaptation in which MHC genes play a crucial role. This review first highlights the dynamics and complexity of parasite-mediated selection in natural systems, which not only depends on dominating parasite strategies and on the taxonomic diversity of the parasite community but also includes the differences in parasite communities between habitats and niches, creating divergent selection on locally adapted populations. Then the different ways in which MHC genes potentially allow vertebrates to respond to these dynamics and to adapt locally are outlined. Finally, it is proposed that varying selection strength in time and space may lead to variation in the strength of precopulatory reproductive isolation which has evolved to maintain local adaptation.

MHC-based mate choice combines good genes and maintenance of MHC polymorphism.

Polymorphic genes of the major histocompatibility complex (MHC) are regarded as essential genes for individual fitness under conditions of natural and sexual selection. To test this hypothesis, we investigated the ultimate individual fitness trait--that of reproductive success. We used three-spined sticklebacks (Gasterosteus aculeatus) in seminatural enclosures, located in natural breeding areas where the experimental fish had been caught. During their reproductive period, fish were exposed continuously to their natural sympatric parasites. By genotyping almost 4000 eggs with nine microsatellites, we determined parenthood and inferred female mating decision. We found that with reference to their own MHC profile, female sticklebacks preferred to mate with males sharing an intermediate MHC diversity. In addition, males with a specific MHC haplotype were bigger and better at fighting a common parasite (Gyrodactylus sp.). This translated directly into Darwinian fitness since fish harbouring this specific MHC haplotype were more likely to be chosen and had a higher reproductive output. We conclude that females also based their mating decision on a specific MHC haplotype conferring resistance against a common parasite. This identifies and supports 'good genes'. We argue that such an interaction between host and parasite driving assortative mating is not only a prerequisite for negative frequency-dependent selection--a potential mechanism to explain the maintenance of MHC polymorphism, but also potentially speciation.

Disentangling the role of MHC-dependent 'good genes' and 'compatible genes' in mate-choice decisions of three-spined sticklebacks Gasterosteus aculeatus under semi-natural conditions.

To investigate and disentangle the role of major histocompatibility complex (MHC)-based 'good genes' and 'compatible genes' in mate choice, three-spined sticklebacks Gasterosteus aculeatus with specific MHC IIB genotypes were allowed to reproduce in an outdoor enclosure system. Here, fish were protected from predators but encountered their natural parasites. Mate choice for an intermediate genetic distance between parental MHC genotypes was observed, which would result in intermediate diversity in the offspring, but no mate choice based on good genes was found under the current semi-natural conditions. Investigation of immunological variables revealed that the less-specific innate immune system was more active in individuals with a genetically more divergent MHC allele repertoire. This suggests the need to compensate for an MHC-diminished T-cell repertoire and potentially explains the observed mate choice for intermediate MHC genetic distance. The present findings support a general pattern of mate choice for intermediate MHC diversity (i.e. compatible genes). In addition, the potentially dynamic role of MHC good genes in mate choice under different parasite pressures is discussed in the light of present and previous results.

[Pneumonia above 80 years, admitted to the hospital]. / Neumonía en el anciano mayor de 80 años con ingreso hospitalario.

OBJECTIVE: To analyze and compare differences in patients older than 80 years with Community acquired Pneumonia admitted in Internal Medicine or Pneumology of a General Hospital from the Emergency Room. MATERIAL AND METHODS: Retrospective study of all the 277 patients above 80 years admitted into the Hospital in 2005 with the main diagnosis of Pneumonia. RESULTS: 84% community-acquired, 16% from Institutions. Mean age: 85.8 y (48% men, 52% women). 19% FINE-3, 49% FINE-4, 32% FINE-5. Known etiology: 25% (Pneumococcal 19%, H. Influenzae and other Gram (-) 6%. 75% treated by Internists, 22% treated by Pneumologists. Standard Guidelines followed up by 30,5% a variant 60% (Equal by Internists or Pneumologists). Time door-1st antibiotic dose 6.6 hours. Global Mortality 16.7%. Women died at 87.4 y, men at 84.5 y (p = 0.035). Mortality FINE 3-4-5: 4.5, 12.4, 30% respectively. Mortality treated before 4 hours: 34.6%, after 4 hours: 11.5% (p = 0.01). Many more FINE 5 cases in Int. Medicine than Pneumology. Mortality by Internists 22%. Mortality by Pneumologists 3% (p = 0.001). Mortality similar following strict guidelines or variant. CONCLUSIONS: a) Internist receive patients sicker than Pneumologists; b) Important mortality in these very old patients of 16.7%, and progressive according the FINE severity index, in spite of correct therapy; c) Rapid initiation of Antibiotics did not decreased mortality; d) Mortality did not change following strict or variant Guidelines; and e) There are areas of quality improvement in our Hospitals.

Neumonía en el anciano mayor de 80 años con ingreso hospitalario / Pneumonia above 80 years, admitted to the hospital

Objetivo: analizar y comparar diferencias en pacientes mayores de 80 años con Neumonía Adquirida en la Comunidad (NAC) como diagnóstico de alta en pacientes ingresados desde Urgencias a servicios de Medicina Interna (MEDIN) y Neumología (NEUMO) de un Hospital General. Material y métodos: análisis retrospectivo de todos los 277 pacientes mayores de 80 años con ingreso hospitalario por NAC en el 2005. Resultados: 84% Comunitarios. 16% de Instituciones. Edad media: 85,8 años (52% mujeres). Severidad: 19% FINE-3. 49% FINE-4. 32%FINE-5. Etiología conocida 25% (Neumocócica 19%, H. Influenzae y otros Gram (-) 6%). 75% trata MEDIN, 22% NEUMO. Guías Clínicas de tratamiento estrictas 30’5%, una variante 60% (Igual en MEDIN que en NEUMO). Tiempo puerta-1ª dosis antibiótico fue de 6,6 horas. Mortalidad:16,7%. Edad fallecidos mujeres: 87,4 a. mayor que hombres: 84,5a. (p = 0,035). Mortalidad FINE-3-4-5: 4,5, 12,4, 30% respectivamente. Mortalidad tratados antes de 4 horas: 34,6%, después de 4 horas: 11,5% (p = 0,01). Mucho más FINE-5 en MEDIN que en NEUMO. Mortalidad MEDIN: 22%, Mortalidad NEUMO: 3% (p = 0,001). Mortalidad igual siguiendo la Guía Clínica o variante. Conclusiones: a) MEDIN recibe pacientes más graves que NEUMO; b) mortalidad importante (16,7%) y progresiva en la escala FINE, a pesar de tratamiento correcto; c) la rápida administración de antibióticos no redujo la mortalidad; d) la mortalidad no varía aún con variantes de las Guías Clínicas; y c) hay areas de mejora en nuestros Servicios

Objetive: To analize and compare differences in patients older than 80 years with Community acquired Pneumonia admitted in Internal Medicine or Pneumology of a General Hospital from the Emergency Room. Material and methods: Retrospective study of all the 277 patients above 80 years admitted into the Hospital in 2005 with the main diagnosis of Pneumonia. Results: 84% community-acquired, 16% from Institutions. Mean age: 85.8 y (48% men, 52% women). 19% FINE-3, 49% FINE-4, 32% FINE-5. Known etiology: 25% (Pneumococcal 19%, H. Influenzae and other Gram (-) 6%. 75% treated by Internists, 22% treated by Pneumologists. Standard Guidelines followed up by 30,5% a variant 60% (Equal by Internists or Pneumologists). Time door-1st antibiotic dose 6.6 hours. Global Mortality 16.7%. Women died at 87.4 y, men at 84.5 y (p = 0.035). Mortality FINE 3-4-5: 4.5, 12.4, 30% respectively. Mortality treated before 4 hours: 34.6%, after 4 hours: 11.5% (p = 0.01). Many more FINE 5 cases in Int. Medicine than Pneumology. Mortality by Internists 22%. Mortality by Pneumologists 3% (p = 0.001). Mortality similar following strict guidelines or variant. Conclusions: a) Internist receive patients sicker than Pneumologists ; b) Important mortality in these very old patients of 16.7%, and progressive according the FINE severiy index, in spite of correct therapy; c) Rapid initiation of Antibiotics did not decreased mortality; d) Mortality did not change following strict or variant Guidelines; and e) There are areas of quality improvement in our Hospitals

Individual MHC class I and MHC class IIB diversities are associated with male and female reproductive traits in the three-spined stickleback.

Genes of the major histocompatibility complex (MHC) are indispensable for pathogen defence in vertebrates. With wild-caught three-spined sticklebacks (Gasterosteus aculeatus) we conducted the first study to relate individual reproductive parameters to both MHC class I and II diversities. An optimal MHC class IIB diversity was found for male nest quality. However, male breeding colouration was most intense at a maximal MHC class I diversity. One MHC class I allele was associated with male redness. Similarly, one MHC class IIB allele was associated with continuous rather than early female reproduction, possibly extending the reproductive period. Both alleles occurred more frequently with increasing individual allele diversity. We suggest that if an allele is currently not part of the optimum, it had not been propagated by choosy females. The parasite against which this allele provides resistance is therefore unlikely to have been predominant the previous year - a step to negative frequency-dependent selection.

[Attitudes of primary care health staff to the mentally ill patient, psychiatry and the mental health team]. / Actitudes del personal sanitario de atención primaria hacia el enfermo mental, la psiquiatría y el equipo de salud mental.

OBJECTIVES: To measure the reliability of a questionnaire on attitudes and knowledge of mental health and the mental health team (MHT). To find out what these attitudes are and their associations with demographic and work variables. DESIGN: Observational, transversal. SETTING: Primary care (PC) centres in an urban environment. PARTICIPANTS: Health staff (n=141) of PC centres whose mental health centres (MHC) for referral are in an area of Guipuzcoa. MAIN MEASUREMENTS: Self-administered, anonymous questionnaire including a section with social, demographic and work data. Survey including items on attitudes towards the mentally ill, psychiatry, the MHCs, staff's perception of their own knowledge and their attitude towards attending courses on the subject. RESULTS: The reply rate was 70%. The factorial analysis had 5 factors whose measurements and scores were: "attendance at courses", 30.8 (8-40); "knowledge", 17.5 (7-35); "more treatment", 12.2 (6-30); "less treatment", 14.4 (5-25); "care through the MHC", 11.5 (4-20). The internal consistency of the 5 scales was 0.95, 0.92, 0.85, 0.83, and 0.65, respectively. 13% did not think you had to be on the look out for the mentally ill. CONCLUSIONS: No negative attitude towards the mentally ill was perceived. PC health staff perceived their lack of psychiatric knowledge and that they did not have sufficient dealings with the MHC, and showed good predisposition towards improving both questions.

[Respiratory disorders among fishermen]. / Alteraciones respiratorias de los trabajadores de la mar.

BACKGROUND: Information concerning to the habits and diseases of sea fishermen is scarce. The respiratory disorders and the risk groups in fishermen from the province of Guipúzcoa, Spain were evaluated in this study. METHODS: A descriptive transversal study (questionnaire and spirometry) and retrospective review of the data on laboral disability and mortality were carried out. RESULTS: The prevalences of chronic bronchitis, asthma and smokers were found to be 18.3%, 9.8% and 47.5% respectively; with a history of pneumonia being 8.9%, tuberculosis 7.3%, pleural disease 5.5%, rib fracture 10.6%, and obstructive disorder 8.9%. Smoking, followed by the presence of previous infectious, were the factors most associated to the presence of respiratory disease. The most prevalent smoking habit observed among the high sea fishermen did not completely explain the greater prevalence of chronic bronchitis found among these subjects. The number of years working at sea was not related to any disorder. Tumors represented the first cause of mortality (34.9%) with those of the trachea, bronchials and lung heading the list (13.3%). Laboral disability due to respiratory causes occupied the third place in the global population (13.0%) and the first place in high sea fishermen (22.2%). In relation with coastal fishermen, the high sea fishermen presented a lower Tiffeneau index and a greater prevalence of smoking, chronic bronchitis, history of tuberculosis and laboral disability, number of medical consultations and admissions due to respiratory problems. CONCLUSIONS: Sea fishermen present a high prevalence of respiratory disease. Differences were observed between high sea and coastal fishermen with the former demonstrating a lower Tiffeneau index and a greater frequency of smoking, chronic bronchitis, tuberculosis history and laboral disabilities, number of medical consultations and admissions for respiratory causes.

[The principal causes of mortality in young people in the Autonomous Community of Madrid: 1990-1991]. / Principales causas de mortalidad en jóvenes en la Comunidad Autónoma de Madrid: 1990-1991.

Our objective is to quantify the mortality from AIDS, narcotic related deaths, and traffic accidents among those between 15 and 39 years of age, in the Community of Madrid, 1990-1991. Data provided by the Regional Register of AIDS, Forensic Institute of Madrid, local police teams and the Traffic Directorate General have been used. Mortality from traffic accidents ranked first as a cause of death, followed by narcotic-related deaths and AIDS, both for men and women.

[Intravenous drug addiction and the risk of HIV infection in Madrid in 1990]. / Drogadicción intravenosa y riesgo de infección por VIH en Madrid 1990.

As part of a multicenter WHO study on HIV infection among drug injectors, 472 intravenous drug users (IDUs) were interviewed, 240 recruited in the streets and 232 at drug treatment centers. The objectives of the study were to assess the prevalence of HIV infection among IDUs of Madrid, to identify factors associated with risk reduction behaviors, such as the use of sterile syringes and condoms. Chi-square and logistic regression were used to test for differences and to estimate odds ratios. Prevalence of HIV infection among IDUs in Madrid was 50% (53% among those recruited in the street and 38% among those recruited at treatment centers). Forty five per cent of those interviewed were still sharing syringes. Out of the 315 sexually active subjects, only 22% reported using condoms always or almost always. These results suggest that a range of interventions should be implemented to promote change towards healthier behaviors, including syringe-exchange programs, methadone maintenance treatments and pre- and post-test counseling in those agencies which care for this population.