Hepatitis B, C, and D Virus Infections and AFP Tumor Marker Prevalence Among the Elderly Population in Mongolia: A Nationwide Survey / 예방의학회지

Objectives@#Infections with hepatitis B, C, and D virus (HBV, HCV, and HDV) are a major public health problem and lead to serious complications such as cirrhosis and hepatocellular carcinoma. We aimed to determine the seroprevalence of hepatitis B surface antigen (HBsAg), anti-HCV, anti-HDV immunoglobulin G, alpha-fetoprotein (AFP), and dual and triple hepatitis virus infections in Mongolia. @*Methods@#A total of 2313 participants from urban and rural regions were randomly recruited for this cross-sectional study. A questionnaire was used to identify the risk factors for hepatitis virus infections, and the seromarkers were measured using immunoassay kits. @*Results@#Among all participants, the prevalence of HBV, HCV, and HDV was 15.6%, 36.6%, and 14.3%, respectively. The infection rates were significantly higher in females and participants with a lower education level, rural residence, older age, and a history of blood transfusion. HBV and HCV co-infection was found in 120 (5.2%) participants and HBV, HCV, and HDV triple infection was detected in 67 (2.9%) participants. The prevalence of elevated AFP was 2.7%, 5.5%, and 2.6% higher in participants who were seropositive for HBsAg (p=0.01), anti-HCV (p<0.001), and anti-HDV (p=0.022), respectively. Elevated AFP was more prevalent in participants co-infected with HBV and HCV (5.8%, p=0.023), HBV and HDV (6.0%, p<0.001), and triple-infected with HBV, HCV, and HDV (7.5%) than in uninfected individuals. @*Conclusions@#Nearly half (49.8%) of the study population aged ≥40 years were infected with HBV, HCV, or HDV, and 22.4% had dual or triple infections.

Associations of Breast Cancer Risk Factors with Premenopausal Sex Hormones in Women with Very Low Breast Cancer Risk.

Breast cancer incidence rates are low but rising in urban Mongolia. We collected reproductive and lifestyle factor information and measured anthropometrics and serum sex steroid concentrations among 314 premenopausal women living in Ulaanbaatar, Mongolia. Mean differences in hormone concentrations by these factors were calculated using age-adjusted quadratic regression splines. Estrone and estradiol in college-educated women were, respectively, 18.2% (p = 0.03) and 23.6% (p = 0.03) lower than in high-school-educated women. Progesterone concentrations appeared 55.8% lower (p = 0.10) in women residing in modern housing compared with women living in traditional housing (gers), although this finding was not statistically significant. Testosterone concentrations were positively associated with adiposity and central fat distribution % difference for highest vs. lowest quarter for body mass index (17.1% (p = 0.001)) and waist-to-height ratio (15.1% (p = 0.005)). Estrogens were higher in the follicular phase of women who breastfed each child for shorter durations. A distinct hormonal profile was associated with an urban lifestyle in premenopausal, Mongol women. In particular, heavier, more-educated women living in urban dwellings had higher testosterone and lower estrogen and progesterone levels. Higher breast cancer incidence in urban compared with rural women suggest that the hormonal profile associated with a more traditional lifestyle may be protective among Mongol women.

A cohort study of chronic diseases for Mongolian people: Outline with baseline data of the Moncohort study.

Many Mongolian people suffer from non-communicable chronic diseases. In order to plan preventive strategies against such diseases, we designed a community-based prospective cohort study of chronic diseases, called the Moncohort study, in Mongolia. This is the first nationwide large-scale cohort study of chronic diseases. This paper describes the study's rationale, design and methods with baseline data. Mongolian residents aged ⩾40years were selected nationwide from many geographic regions in 2009. Data were collected on demographics, socioeconomic status, lifestyle, and anthropometric and biochemical measurements. In total, 2280 Mongolian residents were registered in the survey. Socioeconomic, lifestyle, anthropometric and biochemical characteristics were differentiated by gender and geographical area in descriptive data. Aging, low social class, physical inactivity and infrequent fruits intake were positively associated with histories of chronic disease in men, while aging was positively associated with histories of chronic disease in women. Factors associated with chronic diseases reveal gender-oriented strategies might be needed for their prevention. Detailed prospective analyses will illustrate the impact of risk factors on chronic diseases and lead to evidence for designing programs aimed at preventing chronic diseases and related disorders in Mongolia.

Epidemiologic features of metabolic syndrome in a general Mongolian population.

BACKGROUND: Although cardiovascular health is a crucial problem for Mongolian people, little information about metabolic syndrome, which is well known to be associated with the development of cardiovascular disease, is available in Mongolia. The aim of this study was to observe the epidemiological features of metabolic syndrome in a general Mongolian population. METHODS: This cross-sectional study was performed in 1911 general Mongolian subjects (717 men, 1194 women), who were ≥40 years old and free of ischemic heart disease, by using a dataset from a nationwide population-based cohort study in Mongolia. The prevalence of metabolic syndrome, as defined by International Diabetes Federation criteria, was determined. Alcohol consumption, smoking habits, and physical activity were evaluated. Education, marital status, income, and occupation were also examined as factors of socioeconomic status (SES). Their association with metabolic syndrome was determined by logistic regression models. RESULTS: The prevalence of metabolic syndrome was significantly higher in women (n=488, 40.6%) than in men (n=138, 19.4%). The prevalence of metabolic syndrome was high, especially in the Khangai region, in women. Moderate-to-high alcohol consumption was a significantly positively associated factor of metabolic syndrome in men [odds ratio (OR)=2.01; 95% confidence interval (CI) 1.15-3.51; adjusted odds ratio (AOR)=2.41; 95% CI 1.31-4.44] and widowed status was a significantly positively associated factor of metabolic syndrome in women (OR=1.61, 95% CI 1.18-2.18; AOR=1.49, 95% CI 1.07-2.08). CONCLUSIONS: Metabolic syndrome was prevalent in women compared with men among Mongolian adults. Preventive strategies aimed at men with a higher alcohol consumption and women with widowed status may help reduce metabolic syndrome, thereby improving cardiovascular health conditions in Mongolia.

The role of hormones in the differences in the incidence of breast cancer between Mongolia and the United Kingdom.

BACKGROUND: There are striking differences in breast cancer incidence between Asian and western women. Rates vary substantially within Asia also, with Mongolia's even lower than China's. These profound differences have been speculated to be due in part to diet, mediated by circulating hormone concentrations. METHODS: Sex steroid hormone concentrations were measured in women living in Ulaanbaatar, Mongolia and the United Kingdom (U.K.). Diet was obtained by interview and national survey data. Mean hormone differences were compared by country, and systematic variation by number of days since last menstrual period was modeled and adjusted for age and parity; difference in overall area under the curves was assessed. FINDINGS: The diet in Mongolia was higher in meat and dairy than in the U.K. Mean testosterone concentrations were 18.5% lower (p<0.0001) while estradiol concentrations were 19.1% higher (p = 0.02) in Mongolian than British women, adjusted for age and parity. Progesterone was almost 50% higher in Mongolian women (p = 0.04), particularly during the follicular phase and early luteal surge. Hormone concentrations generally were similar in Mongolian women born in Ulaanbaatar compared with those born in rural areas, although there was a decreasing progesterone trend by degree of westernization (rural Mongolia; urban Mongolia; U.K.). Mean hormone differences were similar when restricted to parous women, and with further adjustment for body mass index, height, and smoking status. INTERPRETATION: These data augment accumulating evidence that circulating estrogens are unlikely to explain reduced breast cancer rates in Asia compared with the west, and suggest casting a wider net with respect to biomarkers. Lower testosterone and higher progesterone in Mongolian women raise the possibility that these hormones may be important to consider. In addition, the almost exclusive dietary reliance of Mongolians on meat and dairy argues against beneficial effects of a low-fat diet on circulating hormones explaining international breast cancer differences.

Vitamin D deficiency in reproductive age Mongolian women: a cross sectional study.

Vitamin D production is critical not only for rickets prevention but for its role in several chronic diseases of adulthood. Maternal vitamin D status also has consequences for the developing fetus. This study assessed the prevalence of vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D]<20ng/ml) and insufficiency [25(OH)D=20-29ng/ml] in spring, among reproductive age Mongolian women. Blood was drawn in March and April, 2009 from 420 Mongolian women, 18-44 years of age. Serum 25(OH)D concentrations were measured, anthropometric measurements were performed and information was collected by interview on lifestyle, dietary and reproductive factors. Logarithm-transformed 25(OH)D levels were compared across risk factor categories by analysis of variance. Linear regression analysis was used to assess the independent associations of factors with vitamin D status. Cutaneous vitamin D3 synthesis was assessed between December and July using a standard 7-dehydrocholesterol ampoule model. The vast majority of women 415 (98.8%) had serum 25(OH)D<20ng/ml (50nmol/l) with an additional 4 women (<1%) in the insufficient range (20-29ng/ml); only one women (0.2%) had sufficient levels (>30ng/ml or 75nmol/l). 25(OH)D concentrations were positively and independently associated with educational status and use of vitamin D supplements, but not with other demographic, lifestyle, reproductive, or anthropometric factors. 25(OH)D levels were not associated with dietary factors in this population, as there is little access to foods containing vitamin D in Mongolia. No production of previtamin D3 was observed until March and was maximally effective in April and was sustained through July. These data suggest that the prevalence of vitamin D deficiency in spring among reproductive age women in Mongolia is high. Given the lack of naturally vitamin D-rich food in the diet and limited use of vitamin D supplements, food fortification and/or supplementation with vitamin D should be considered among these women.

A comparison of migrants to, and women born in, urban Mongolia: demographic, reproductive, anthropometric and lifestyle characteristics.

BACKGROUND: Mongolia has experienced vast migration from rural to urban areas since the 1950s. We hypothesized that women migrating to Ulaanbaatar, the capital, would differ in factors related to future chronic disease risk compared with women who were born in Ulaanbaatar. METHODS: Premenopausal mothers (aged <44 years) of children attending two schools (one in the city centre and one in the outskirts) in Ulaanbaatar were recruited for the study. During April and May 2009, 420 women were interviewed about migration, reproductive history and lifestyle factors and anthropometric measurements were taken. RESULTS: Women born in (n=178) and outside (n=242) Ulaanbaatar were similar in education and marital status, but the latter appeared to have a more traditional lifestyle including being more likely to have lived as a nomadic herder (22.3% vs 5.6%; p<0.001) and to currently live in a traditional yurt or ger (40.1% vs 29.2%). Ever-use of hormonal contraception was more common in women born outside Ulaanbaatar (52.1% vs 38.2%; p=0.005) and their age at first live birth was older (26.0% vs 20.8% for ≥ 25 vs <25 years). Although the number of pregnancies was similar, the number of live births was greater for those born outside Ulaanbaatar (p=0.002). Women born in Ulaanbaatar were more likely to have smoked cigarettes (24.7% vs 11.2%; p<0.001). Women born outside Ulaanbaatar were more likely to consume the traditional meat and dairy diet. CONCLUSION: Rural migrants to Mongolia's capital have retained a traditional lifestyle in some, but not all, respects. Internal migrant populations may provide the opportunity to assess the effect of changes in isolated risk factors for subsequent chronic disease.

Hypertension in Mongolia: an overview.

OBJECTIVES: Although hypertension is the primary cause of morbidity and mortality from cardiovascular diseases in Mongolia, reviews about hypertension in this country have not been reported, to our knowledge. Information on the overview of this disease may be useful to establish measures and policy to prevent hypertension and its related complications. The aim of our article is to summarize the current situation vis-à-vis hypertension in Mongolia. METHODS: Population-based studies that provided relevant information on hypertension in Mongolia were searched through PubMed, abstract books of the Mongolian Medical University resources from cardiologists, epidemiological databases and reliable websites of national organizations. Available articles from 1970 to present were selected. RESULTS: A high prevalence of hypertension, which varied according to geographic location, exists among Mongolian people. The prevalence of hypertension may be influenced by nutritional factors, sedentary lifestyle, socioeconomic status and environmental factors in particular. CONCLUSIONS: The high prevalence of hypertension among Mongolian people can be a serious health problem in this country. Defining ethnic features of hypertension and related conditions will be the initial step that may lead to prevention of this disease. Further research and positive efforts to prevent hypertension appear necessary for Mongolians.

Ischemic heart disease and its related factors in Mongolia: a nationwide survey.

Ischemic heart disease (IHD) remains one of the most important disorders associated with disability and mortality worldwide, and is one of the major causes of cardiovascular diseases in Mongolia. The objective of the current study was to determine the prevalence of IHD and its related factors in a general population in Mongolia. We conducted a nationwide cross-sectional survey between March and September, 2009. General participants were recruited from urban to rural regions in a multistage random cluster sampling method. The diagnosis of IHD was based on the Rose questionnaire (World Health Organization) and electrocardiographic findings. A total of 369 (16.2 %) subjects with IHD were diagnosed among 2,280 participants. The prevalence of subjects with IHD was significantly increased by age: from 9.9 % in individuals age 40-44 years compared to 17.7 % in those over 60 years. Smoking habits (former and current) and non-frequent intake of fruits and vegetables were significantly positively associated with IHD in men, while heavy alcohol drinking habits and lower education period of time were significantly positively associated with IHD in women. IHD was found to be prevalent, especially among people aged over 40 years, in Mongolia. Statistical factors related to IHD were found to be significantly different based on sex. The current data may provide relevant information to prevent IHD in the Mongolian population.

Breast cancer incidence in Mongolia.

PURPOSE: Data on international variation in breast cancer incidence may help to identify additional risk factors. Substantially lower breast cancer rates in Asia than in North America and Western Europe are established, but differences within Asia have been largely ignored despite heterogeneity in lifestyles and environments. Mongolia's breast cancer experience is of interest because of its shared genetics but vastly different diet compared with other parts of Asia. METHODS: Age-standardized breast cancer incidence and mortality rates obtained from the International Association of Cancer Registries are presented for several Asian countries. Mongolian incidence rates obtained from its cancer registry describe incidence within the country. RESULTS: Breast cancer incidence in Mongolia (age standardized 8.0/100,000) is almost a third of rates in China (21.6/100,000), and over five times that of Japan (42.7/100,000) and Russia (43.2/100,000). Rates within Mongolia appear to have increased slightly over the last decade and are higher in urban than rural areas (annual percentage increase of age-standardized rates from 1998 to 2005 was 3.60 and 2.57 %, respectively). The increase in breast cancer incidence with age plateaus at menopause, as in other Asian populations. CONCLUSIONS: Mongolia's low breast cancer incidence is of particular interest because of their unusual diet (primarily red meat and dairy) compared with other Asian countries. More intensive study of potential dietary, reproductive and lifestyle factors in Mongolia with comparison to other Asian populations may provide more clarity in what drives the international breast cancer rate differences.

Kawasaki disease in Mongolia: results from 2 nationwide retrospective surveys, 1996-2008.

BACKGROUND: Kawasaki disease (KD) has been reported in many countries. However, the incidence of KD in Mongolia is not known. This is the first report of incident cases of KD in Mongolia, which were identified using data from 2 nationwide surveys. METHODS: Two nationwide retrospective surveys were conducted: medical histories were collected from patients aged 0 to 16 years who were hospitalized countrywide between 1996 and 2008. Hospital records for these patients were also reviewed. Nationwide training seminars on KD were conducted before each survey. RESULTS: For the nationwide surveys, the participation rates among all hospitals with pediatric wards were 97% and 94%. Inpatient medical histories from 1996 through 2008 were reviewed, and, among children younger than 16 years, 9 patients with KD were investigated. The age of KD patients ranged from 1.4 to 14 years; 7 of 9 patients were male. Six (67%) patients fulfilled all 6 clinical diagnostic criteria; the other 3 (33%) were defined as having KD based on the presence of 5 such criteria. Fever persisting 5 or more days, bilateral conjunctival congestion, and changes of the lips and oral cavity were the most common symptoms, and cervical lymphadenopathy was the least common symptom. Cardiac sequelae developed in 5 of the patients, 4 of whom were older than 10 years. CONCLUSIONS: The results of these nationwide surveys reveal that KD cases do exist in Mongolia. However, knowledge of KD among Mongolian pediatricians is likely to be poor. Thus, there is a need to augment their understanding to improve management of KD patients. Further studies are crucial to clarify the epidemiologic characteristics of KD in Mongolia.

Hepatitis A and E virus infections among children in Mongolia.

To compare the epidemiologic profiles of hepatitis A virus (HAV) and hepatitis E virus (HEV) infections in children in Mongolia, the prevalence of HAV and HEV infections was studied serologically and molecularly among 520 apparently healthy children 7-12 years of age (mean +/- standard deviation, 8.5 +/- 0.8 years) using serum samples obtained in 2004. Total antibody against HAV (anti-HAV) was detected in 438 children (84.2%), whereas IgG antibody against HEV (anti-HEV IgG) was detected in only three subjects (0.6%). All three subjects with anti-HEV IgG were negative for anti-HEV IgM and HEV RNA. The presence of HAV RNA was tested in all 520 subjects, and one child (9-year-old girl) was found to have detectable HAV RNA (subgenotype IA). In conclusion, HEV infection was uncommon, but subclinical HAV infection was highly prevalent among children in Mongolia.

Administration of hepatitis B vaccine in winter as a significant predictor of the poor effectiveness of vaccination in rural Mongolia: evidence from a nationwide survey.

BACKGROUND: Universal hepatitis B (HB) immunisation is the most effective means for prevention of hepatitis B virus (HBV) infection worldwide. Maintaining the vaccine cold chain is an essential part of a successful immunisation programme. Our recent nationwide survey in Mongolia has observed significant urban-rural differences in the prevalence of HBV infection among vaccinated cohorts. OBJECTIVE: To examine whether the administration of HB vaccine in winter contributes to these residential discrepancies on the effectiveness of vaccination. DESIGN AND SETTING: In 2004, a nationwide serosurvey was carried out covering both urban and rural areas of Mongolia. Sampling was multistage, with random probability from all public schools in the country. PARTICIPANTS: A random sample of 1145 children (51.7% boys; aged 7-12 years), representative of Mongolian elementary school children. RESULTS: Multivariate logistic regression analysis identified that total (past and current) HBV infection (OR 2.31, 95% CI 1.20 to 4.42; p = 0.012) was independently associated with the administration of all HB vaccines in winter. An increased OR for current HBV infection was also observed (OR 2.58, 95% CI 0.87 to 7.68; p = 0.089), but without significance. Interestingly, after stratifying by residence, the association between winter vaccination and total HBV infection was evident for rural (p = 0.008) but not for urban areas (p = 0.294). The frequency of vaccine-induced immunity was significantly (p = 0.007) lower for those who received HB vaccine at birth during winter in rural areas. CONCLUSION: Administration of HB vaccine during winter is an important predictor of the low effectiveness of vaccination in rural Mongolia. To improve the effectiveness of HB vaccination in remote areas, cold chain control should be addressed with particular attention to the winter season.

Impact of the universal hepatitis B immunization program in Mongolia: achievements and challenges.

BACKGROUND: The impact of the universal infant hepatitis B (HB) immunization program initiated in 1991 in Mongolia is still unclear. METHODS: A nationwide school-based cross-sectional serosurvey was conducted in 2004, with stratified, multistage, random cluster sampling from all public elementary schools (n=593) in Mongolia. All children were tested for serological markers of hepatitis B virus (HBV). RESULTS: Serology results were available for 1,145 children (592 boys and 553 girls) aged 7-12 years (survey response rate: 93%). Immunization card was available for 702 (61.3%) children. The coverage of complete HB vaccination was 60.1% and it was increased by birth cohort from 44% to 76%. Significantly higher proportion of children in Metropolitan cities (75.2%) was completely vaccinated with HB compared to those in Province centers (55.7%) and rural areas (59.1%). HBV infection occurred in 5.9%, 13.2%, and 20.8% of complete vaccinees living in Metropolitan, Province centers, and rural areas, respectively; of whom 1.2%, 2.9%, and 8.6% were HB surface antigen (HBsAg) carriers, respectively. Only 17.0% of the children had protective anti-HBs which decreased from 31.1% to 16.3% among 7 to 12-year-olds indicating its decay with time. CONCLUSIONS: Prevalence of HBV infection and carriage among young generation meaningfully declined compared with those of previous studies in Mongolia. The coverage of birth dose and complete HB vaccination was significantly low in Province centers and rural areas which should be taken into consideration.

Seroepidemiology of hepatitis B virus infection among children in Mongolia: results of a nationwide survey.

BACKGROUND: Because Mongolia is one of the highly endemic countries for hepatitis B virus (HBV) infection in the world, hepatitis B (HB) vaccine was introduced into the National Expanded Program on Immunization in 1991. However, relatively few data are available concerning HBV infection among children born after the start of the program, so far. The aim of the present paper was to describe the seroepidemiology of HBV infection among primary school children using representative national data. METHODS: In 2004, a nationwide school-based cross-sectional serosurvey was carried out throughout Mongolia, covering both urban and rural areas. Serum samples were tested for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc) and hepatitis B e antigen (HBeAg) as well as for liver enzymes. RESULTS: A total of 1145 children aged 7-12 years were studied, which represents nearly 2% of the second grade population of elementary schools in Mongolia. The overall prevalence of HBsAg and anti-HBc was 5.2% (95% confidence interval [CI]: 3.9-6.5%) and 15.6% (95%CI: 13.5-17.7%), respectively. Among HBsAg-positive children 67.8% (95%CI: 55.9-79.7%) were also positive for HBeAg. The prevalence of chronic HBV infection increased by age and was significantly higher among children from rural areas compared to those from urban areas (7.7% vs 3.0%; P < 0.001). In the multivariate logistic regression analysis, rural residence (odds ratio [OR]: 2.57; 95%CI: 1.45-4.58), male sex (OR: 1.9; 95%CI: 1.08-3.26) and age (OR: 1.5; 95%CI: 1.10-2.05) were independent demographic predictors for chronic HBV infection. CONCLUSIONS: The prevalence of chronic HBV infection has been decreasing in the Mongolian young generation, most likely due to infant HB vaccination. However, significant rural-urban differences in the prevalence of HBV infection were found that demand further investigation to estimate the potential causes.

Hepatitis delta virus infection in mongolia: analyses of geographic distribution, risk factors, and disease severity.

The prevalence and risk factors for hepatitis delta virus (HDV) infection among Mongolian school children were assessed by detecting the antibody against HDV and HDV RNA, and through structured interviews. The study subjects consisted of 181 children with the past or ongoing hepatitis B virus infection who were investigated during the nationwide serosurvey conducted in 2004. The prevalence of antibody to HDV was 6.1%, with the proportion of 13.6% among hepatitis B surface antigen (HBsAg)-positive subjects, all of whom had HDV RNA. Multivariate logistic regression analyses showed that injections (> 11 times) (odds ratio [OR] = 8.31, 95% confidence interval [CI] = 1.28-54.07) and blood sampling (> 3 times) (OR = 5.34, 95% CI = 1.12-25.53) in health care settings, hospitalization (> 3 times) (OR = 6.20, 95% CI = 1.18-32.71), and cohabitating with patients with chronic hepatitis (OR = 4.57, 95% CI = 1.26-16.55) predicted the seropositivity for antibody to HDV. These results suggest that parenteral exposures in health care settings and household transmission are the main routes of HDV transmission among Mongolian children.

Prevalence and risk factors for hepatitis C virus infection in Mongolian children: Findings from a nationwide survey.

Although the hepatitis C virus (HCV) infection is one of the major causes of chronic hepatitis and hepatocellular carcinoma (HCC) in Mongolia, its prevalence among children and routes of transmission are largely unknown. The aim of the study was to determine the prevalence of anti-HCV antibodies and the possible risk factors for transmission among school children using representative national data. A nationwide cross-sectional survey among elementary school children was conducted in four main geographical regions and the metropolitan area of Mongolia, through multistage, stratified, random cluster sampling. Serum samples from 1,145 children (response rate, 93%; 592 boys and 553 girls; age range, 7-12 years), which represented nearly 2% of the second grade population in Mongolia, were tested for HCV antibodies with a third-generation immunoradiometric assay (IRMA). Positive samples were further evaluated by a third-generation immunoblot assay (RIBA). A standardized questionnaire concerning the socio-demographic characteristics and potential risk factors was used. Overall, seven subjects were confirmed to be anti-HCV seropositive, giving a prevalence of 0.6% (95% CI: 0.15-1.0%). The prevalence of anti-HCV increased with age. In the multivariate logistic regression analysis, adjusted for age, sex, and residence, the history of dental manipulation (odds ratio [OR] = 15.4; 95% CI: 1.4-164.8) and surgery (OR = 8.3; 95% CI: 1.5-45.6) were associated independently with the presence of anti-HCV. These findings suggest that contaminated equipment used in the dental and surgical manipulations probably played a predominant role in HCV transmission among Mongolian children. Strict guidelines on disinfection and sterilization procedures of medical instruments have to be introduced and should be followed to improve the control of HCV infection in Mongolia.