مجله اپیدمیولوژی ایران
پیاپی 2 (زمستان 1384)

Zoonoses are disease and/or infection naturally transmissible between vertebrate animals and humans. Emerging zoonoses are defined by the WHO/FAO/OIE joint consultation on emerging zoonotic disease held in Geneva, 3-5 may 2004 as "diseases which are newly recognized or newly evolved or that have occurred previously but show an increase in incidence or expansion in geographical, host or vector range". The number of emerging zoonoses has increased dramatically over the last few decades, with potentially serious human and economic impact worldwide. Many factors are behind the emergence of these zoonotic diseases. Intensive animal husbandry and changes in the production and distribution of food and other commodities, climatic and environmental changes, rapid transportation of human and animals, changes in life style and increased animal contacts are some of the factors that could introduce a new disease in a particular area. Viral infectious agents are more prone to mutation and sudden or gradual change and expansion to new geographical areas or hosts. In this article we briefly discuss some of the zoonotic diseases which may have potential health effects in Iran, such as avian influenza, West Nile viruses, Rift Valley fever, Congo-Crimean hemorrhagic fever, Lassa fever, Sars, and Ebola Marburg hemorrhagic disease.

Breast cancer is a common malignancy in women in many parts of the world. The incidence of breast cancer in Iranian women is growing. Iranian patients are relatively younger than their western counterparts. We conducted a case-control study to determine roles of reproductive factors for breast cancer among women in Iran. A hospital based case-control study was conducted in 2004 at a teaching hospital in Tehran, Iran. A total of 303 cases of breast cancer and 303 healthy controls were interviewed. Cases were identified through the oncology department of a university hospital and controls were recruited from other wards or out-patients clinics at the same hospital. Controls were matched to cases on age. Demographic and reproductive data were ascertained by personal interview using a structured questionnaire. Informed consent was obtained from cases and controls. Odds ratios and 95% confidence intervals for breast cancer were derived using logistic regression analysis. Mean ±SD age of cases and controls was 48.8 ±9.8 and 50.2 ± 11.1 years, respectively (range 24-84). The final model constructed after multivariate analysis indicated that factors such as never being married, menopause, older age at first live birth, parity, use of oral contraceptives, and history of chest X-ray between adolescence and the age of 30 yrs were significantly associated with breast cancer. Variables such as higher education, early age at menarche, abortion, breast feeding and its duration did not constitute significant risk factors. Marital status, history of chest X-ray between adolescence and the age of 30, number of live births, and age at first live birth, menopause, and oral contraceptive use seem to increase the risk of developing breast cancer among women in Iran.

Kala azar is a parasitic disease which belongs to the category of metazoonoses (a communicable disease which requires at least to an invertebrate host), In Iran canines are major reservoir for it and most of patients are 6 months to 2 years old. The aim of this study was evaluation of the clinical and epidemiologic aspects of visceral leishmaniasis in patients visiting the Children Medical Center over the 12 past years. This study used the hospital records of a case series of 106 kala azar patients hospitalized in the Children's Medical Center between 1991 and 2001. We extracted and analyzed data on geographical location, background factors, clinical and laboratory findings, response to treatment and Glucantimeâ side effects. The greatest number of cases was seen in 1992 and the smallest number in 1993 and 2003; the number of cases peaked in the spring. Most patients referred to the Center are aged 1 to 4 years, and there is a strong preponderance of males (82.1% vs 17.9%). The majority of these children came from families in which the breadwinner was a peasants or a laborer. Common laboratory findings included anemia, rising ESR titers and thrombocytopenia. The most striking clinical signs and symptoms were fever, splenomegaly and hepatomegaly. Eighty-three percent of the patients had shown clinical improvement, 1.9% had died and 15.1% had relapsed. Moreover, in 52.8% of cases, the disease was treated successfully with within 2 weeks; the incidence of Glucantimâ side effects was low. The cities of Khorramabad, Karaj and Saveh had produced the greatest numbers of cases. Compared to other studies, our case series showed a higher proportion of male patients and a somewhat different clinical and laboratory profile. However, the most important achievement of this study was identification of major endemic foci in Ardabil province, northwestern parts of Ghom province, Khorramabad, and regions located south of the Alborz Mountains (e.g. Saveh).

Malnutrition is a major health problem in Iran. A nationwide survey (ANIS) in 1998 revealed that over 800 000 children in this country were suffering from moderate or severe malnutrition. The southern province of Hormozgan is one of the most severely affected regions, so there is a need to determine disease associations and risk factors for child malnutrition in this area. In this case-control study, we selected 1725 children aged 6 to 30 months from both rural and urban areas of Hormozgan. Data for the study were obtained by filling questionnaires and studying family health files. Using the weight-for-age Z score (WAZ) as outcome measure, we examined the effects of 21 different variables, including putative risk factors, confounders, and background variables. Father's job (p<0.004), parent's education, interval between pregnancies, urban versus rural residence (p<0.001), family size (p<0.03), and misconceptions regarding the growth chart were recognized as risk factors for malnutrition. Moreover, the mean age of the cases was 2.3 years higher than that of the controls (p<0.001). Complete vaccination (p<0.018) and attending day care centers (p<0.005) emerged as protective factors. Poverty (low-income jobs, rural residence, large family size, etc) is an important factor causing malnutrition among children in Hormozgan. In contrast, immunization and mother's knowledge of the child's growth chart are major protective factors. Therefore, the health system must continue its support for the current immunization program. It should also try to improve the quality of its health education programs targeted at mothers attending state-run health and medical clinics.

The DPT vaccine used in Iran is manufactured by the Razi Institute. So far, there have been no studies to determine the incidence and severity of adverse reactions to this vaccine. It was this lack of reliable information, plus concern for the unfavorable effects of such reactions on compliance with the vaccination schedule, that prompted the current study on DPT side effects. In this cohort study, 1910 children aged 0 to 6 were divided into different groups (cohorts) on the basis of factors such as injection site and then monitored for the appearance of adverse effects. Data for this study were gathered through questionnaires filled by telephone or house-to-house interviews. We interviewed parents of children attending the 46 urban health clinics in Kermanshah. These interviews produced the data needed to fill the first part of the study questionnaire. The investigators then gave each parent an "information sheet" containing the data necessary for the second part of the questionnaire. The interviewee was asked to record on this sheet any adverse effects occurring over the following 48 hours. At the end of this period, the parent was contacted via telephone to fill the second part of the questionnaire. Data thus gathered were analyzed using the Statistical Package for Social Sciences (SPSS), version 11.5. In 1910 DTP immunizations given to children 0 to 6 years of age, followed for the development of adverse events occurring within 48 hours after immunization, the cumulative incidence rates were as follows: Swelling, 40.66% (38.43-42.89%); Redness, 43.08% (40.84-45.32%); Pain, 67.32% (65.20-69.40%); Fever (>38° C) 54.14% (51.89-56.40%); Fever (>40.5° C) 1.11% (0.64-1.59%); Drowsiness, 33.35% (31.21-35.48%); Persistent crying, 13.35% (11.81-14.88%); Local reactions, 75.79% (73.86-77.73%) and Systemic Reactions, 69.84% (67.76-71.97%). Only one child developed convulsion following immunization. Varying reaction rates in different studies, such as high rate of pain and persistent crying in this study, may reflect the different preparations that were used or differenced in the methods for vaccine evaluation. Moreover, because of the severity of systemic reactions, DTP vaccine should be administered in the thigh region.

Logistic regression is one of the most widely used generalized linear models for analysis of the relationships between one or more explanatory variables and a categorical response. Strong correlations among explanatory variables (multicollinearity) reduce the efficiency of model to a considerable degree. In this study we used latent variables to reduce the effects of multicollinearity in the analysis of a case-control study. Our data came from a case-control study in which 300 women with breast cancer were compared to 300 controls. Five highly correlated quantitative variables were selected to assess the effect of multicollinearity. First, an ordinary logistic regression model was fitted to the data. Then, to remove the effect of multicollinearity, two latent variables were generated using factor analysis and principal components analysis methods. Parameters of logistic regression were estimated using these latent as explanatory variables. We used the estimated standard errors of the parameters to compare the efficiency of models. The logistic regression based on five primary variables produced unusual odds ratio estimates for age at first pregnancy (OR=67960, 95%CI: 10184-453503) and for total length of breast feeding (OR=0). On the other hand, the parameters estimated for logistic regression on latent variables generated by both factor analysis and principal components analysis were statistically significant (P<0.003). The standard errors were smaller than with ordinary logistic regression on original variables. The factors and components generated by the two methods explained at least 85% of the total variance. This research showed that the standard errors of the estimated parameters in logistic regression based on latent variables were considerably smaller than that of model for original variables. Therefore models including latent variables could be more efficient when there is multicollinearity among the risk factors for breast cancer.

Ecstasy is a methamphetamine derivative becoming increasingly popular throughout the world, particularly among adolescents and young adults. Iran, situated between eastern and western societies, can serve as a significant source of information on ecstasy use and on the user's profile. The purpose of this study was to determine the prevalence of ecstasy use and high-risk behavior among high school students in Lahidjan. We conducted a cross-sectional study of a representative sample drawn from high school students of Lahidjan in 2005, using multi-stage stratified random sampling. The study questionnaire was administered to 2345 students in grades 8 through 12. The questionnaire was adapted from that used in "Monitoring the future" projects in the United States and ESPAD (The European School Survey Project on Alcohol and other Drugs). It included questions on demographic characteristics, family profile, social contacts, school life and the use of drugs. Data analysis was done with the SPSS software (version11.5), using χ2 tests and logistic regression methods. Of the 2345 students selected for the study, 2328 (92%) responded. Of these, 1327 (57.8%) were males and 970 (42.2%) were females. Lifetime prevalence of ecstasy use was 2.4% (55 students); 31 subjects had used ecstasy within the past month and 24 students reported using the substance in the preceding year. Ninety-two subjects (4.2%) had experience with other drugs. In χ2 tests, ecstasy use was significantly associated with gender, use of other substances, cigarette smoking, partying with friends, family structure and poor school performance in the past. There was no association with age, type of school (private or public) or the family's education level.In logistic regression, factors influencing ecstasy use were the use of other drugs, cigarette smoking and partying with friends (p< 0.0001). Ecstasy use appears to be a serious problem in high schools. Whatever the causes behind the rise in ecstasy use, personalized and informative educational interventions should be organized in all schools.

Although most occupational injuries are the result of stress-related human error, the association between job stress and work-related accidents has not been studied adequately. The aim of this study, carried out in 2004, was to look at the pattern of job stress among workers at Iran-Saipa car manufacturing plant, and to assess the relationship between stress and occupational injuries. Data were collected randomly from 608 workers considered to be at risk. The sample was composed of 100 subjects with a history of work-related injury within the preceding year and 508 subjects without such history. Job stress was assessed by the Belkic Occupational Stress Index (OSI). We performed creatinine, cortisole, and 17-ketosteroid assays on 24-hour urine collection samples to check the validity of OSI questionnaires. All subjects were males. The prevalence of job stress was 21.3%. The main stressors were time pressure (78.5%), mode of payment and evaluation (56.4%), and interaction with people and machines (41.3%). The risk of injury for workers experiencing job stress was significantly higher than in those without job stress (odds ratio= 2.0). On the other hand, job stress was found to be responsible for 11.9% of all occupational injuries in this community. In conclusion, job stress should be recognized as an important factor causing occupational injuries among car manufacturing workers. Full commitment and participation of managers at all levels and also behavioral and environmental modifications in the production line is important in promoting safety and injury prevention.