Community-based cross-sectional seroprevalence study of hepatitis A in Bangladesh

AIM: To elucidate the age-distribution of anti-hepatitis A virus (HAV) seroprevalence across different socioeconomic status (SES) categories in Bangladesh which,despite scarce data, is generally deemed to have high endemicity.METHODS: Blood samples of 818 subjects from a strati-fied sample of schools and hospitals, comprising different age categories and SES were collected. They were assayed for total anti-HAV antibodies. Social and medical history data were obtained using a questionnaire.RESULTS: Overall anti-HAV seroprevalence was 69.6%, increasing with age from 1-5 years (40.4%) to > 30 years (98.4%). Seroprevalence was lowest (49.8%) in the high SES group and highest (96.5%) in the rural lower-middle SES group. Among subjects aged 6-20 years, anti-HAV seroprevalence was lowest in urban private school children (43.0%), followed by urban government school children (76.2%) and rural school children (96.5%) ( P < 0.01). Within the high SES group, anti-HAV seroprevalence was 32.3% in subjects < 10 years and 51.7% in those aged 11-20 years. Until now Bangladesh has been deemed to have high endemicity for HAV.CONCLUSION: The transition from high to intermediate HAV endemicity may be underway; high SES adolescents and adults remain particularly at risk of symptomatic illness. Preventive measures need consideration.     

Hepatitis A in Latin America: a changing epidemiologic pattern

In a multicenter study, hepatitis A virus (HAV) seroprevalence was surveyed in six countries in Latin America in which in 12,000 subjects were stratified for age. The highest rates of seroprevalence were recorded in the Dominican Republic (89.0%) and Mexico (81.0%), with lower rates in Brazil (64.7%), Chile (58.1%), Venezuela (55.7%), and Argentina (55.0%). The seroprevalence of HAV in children between 1 and 5 years of age was less than 50%, except in the Dominican Republic. In the 5-10-year-old age group, seroprevalence rates have also decreased compared with previous reports. This suggests that the epidemiology is shifting from high to intermediate endemicity, with the population susceptible to HAV infection shifting from children to adolescents and adults. Furthermore, data from Brazil, Argentina, and Mexico show that HAV seroprevalence is significantly lower in people living in medium and high socioeconomic conditions. This study suggests the need for appropriate vaccination programs to be implemented targeting children, adolescents, and adults, particularly in higher socioeconomic groups.     

Current seroprevalence of hepatitis A virus infection among kindergarten children and teachers in Taiwan

Taiwan was a hyperendemic area for hepatitis A virus (HAV) infection before the late 1980s. The seroprevalence of HAV infection was higher than 90% with most HAV infection occurring during childhood. This study was to estimate the seroprevalence of HAV infection among preschool children in central Taiwan. A community-based survey was carried out in 54 kindergartens in 10 urban areas, 10 rural areas and 2 aboriginal areas randomly selected through stratified sampling. Serum samples of 2,549 healthy preschool children and 104 teachers in study kindergartens were screened for the HAV antibodies (anti-HAV) by means of a commercially available microparticle enzyme immunoassay (AxSYM HAVAB). Among aboriginal kindergarten children, more than 96% of them were anti-HAV seropositive due to a mass HAV vaccination program. In urban and rural areas, kindergarten children had a very low prevalence of anti-HAV (0.4%) in contrast to a high seroprevalence in their teachers (78%). There was no gender difference in seroprevalence of anti-HAV, while the anti-HAV seroprevalence was significantly higher in urban areas than in rural areas. Crowdedness of living in urban areas might facilitate the person-to-person transmission of infectious agents.     

Hepatitis a in Lebanon: a changing epidemiological pattern

In this multicenter study in Lebanon, hepatitis A virus (HAV) seroprevalence rates were surveyed by age, gender, and socioeconomic factors. Blood samples collected from 606 subjects aged 1 to 30 years were analyzed for anti-HAV IgG. Age was the most important factor influencing HAV seroprevalence. HAV seroprevalence rates in the current study were about 78% in the > or = 21 years age group, 28% in the 6-10 years age group, and 11% in the 1-5 years age group as compared with 97.7% in adults, 85% in children aged 6-12 years, and 40% in children aged 1 to 5 years in previous studies, demonstrating a shift in HAV seroprevalence from the younger to the higher age groups. In light of the severity of the disease in adults and availability of safe and effective vaccines against HAV infection, introduction of HAV vaccination into the national immunization schedule of Lebanon should be considered.     

Hepatitis A vaccines and the elderly

Hepatitis A virus (HAV) exposure in unprotected adults may cause severe and serious symptoms, with risk of both morbidity and mortality increasing with age. As seroprevalence of HAV is low in industrialised countries, and an increasing number of people, with an increasing median age, travel from areas of low HAV endemicity to high endemicity, pre-travel vaccination is warranted. Vaccination of the elderly against HAV, however, may be associated with reduced seroprotection, since the immune response decreases with age. Studies with monovalent hepatitis A vaccine or combined hepatitis A and B vaccine show good efficacy in adults in general. Few studies have assessed the immune response in older adults. The only prospective study with monovalent hepatitis A vaccine in the elderly showed a reduced seroprotection of approximately 65% after a single primary dose in subjects over the age of 50 years, while seroprotection was 98% in this age group after receiving a booster dose. The only prospective study with combined hepatitis A and B vaccine in younger subjects or older than 40 years showed similar seroprotection (99-100%) against HAV compared to a monovalent vaccine after receiving three doses. As data on seroprotection for HAV in the elderly are limited, further studies are needed to elucidate how optimal protection in the elderly can be achieved. In the mean time, based on the available data, the suggestion is made to screen elderly travellers to areas endemic for HAV for the presence of naturally acquired immunity, and, if found susceptible, be immunised well in advance of their trip, to allow time for post-vaccination antibody testing and/or administration of a second dose of the vaccine.     

Loss of hepatitis A virus antibodies after bone marrow transplantation

Reimmunization guidelines have recommended the inactivated HAV vaccine for hematopoietic stem cell transplant (HSCT) recipients living in or traveling to areas where hepatitis A is endemic. As a shift from high to medium hepatitis A endemicity has been observed in several countries in Latin America, we conducted a retrospective study to evaluate the prevalence of hepatitis A pre-bone marrow transplant (BMT) and the loss of specific antibodies in consecutive stored serum samples from 77 BMT recipients followed up from 82 to 1530 days. The prevalence of HAV antibodies was 92.2% before BMT. As vaccine was not available in Brazil when the samples were taken, it was assumed that this prevalence reflects natural infection. Survival analysis showed that the probability of becoming seronegative was 4.5% (+/-2.6%), 7.9% (+/-3.4%), 10.1% (+/-4.0%), 23.4% (+/-9.6%) at 1, 2, 3 and 4 years after transplant, respectively. The loss of HAV antibodies was significantly associated with longer follow-up (P=0.0015), younger age (P=0.049) and acute graft-versus-host disease (P=0.035). As most reimmunization protocols start around day +365, in developing countries with similar HAV endemicity, BMT recipients should have serological screening before HAV vaccination and the inactivated vaccine should be advised to those seronegative.     

Hepatitis A seroprevalence and its relationship with environmental factors in children of different age groups in Kahramanmaras, Eastern Mediterranean region of Turkey

Hepatitis A infections are influenced by environmental and socioeconomic factors. Epidemiologic studies regarding hepatitis A virus (HAV) infection in Turkey have not previously examined these factors. We investigated HAV seroprevalence and its association with sociodemographic factors among children of various ages in the Eastern Mediterranean region of Turkey. The study included 1142 children (603 male and 539 female) between ages of 6 months and 18 years. Seropositivity in the whole group was 57.2%. HAV prevalence rates according to age groups were as follows: 35.5% in 6-23 months group, 19.2% in 2-5 years group, 74.3% in 6-10 years group, 83.0% in 11-14 years group, 92.8% in 15-18 years group. Risk factors that influenced seropositivity were; dense population, over-crowded families, excessive number of siblings, low socioeconomic status and low education of the mother. As HAV seroprevalence in children older than 6 years of age is high, we recommend hepatitis A vaccination in this region after the first year of life.     

Differences in hepatitis A seroprevalence among geographical regions in Turkey: a need for regional vaccination recommendations

Summary.  Hepatitis A is a worldwide vaccine-preventable infection. Recommendation of vaccination depends on the endemicity of the disease. The World Health Organization recommends universal hepatitis A vaccination in intermediate areas; however, there is no need of mass vaccination in high and low endemicity regions. Therefore, most of the countries are using a vaccination policy according to the endemicity characteristic representing the whole of the country. The endemicity of this infection varies due to sanitary and hygiene conditions and socioeconomic differences among the countries and in various regions of the same country. A sample of 1173 persons between the age of 0 and 91 years from nine randomly selected medical centres from five different geographical centres of Turkey were tested for the level of anti-hepatitis A virus (anti-HAV) immunoglobulin-G antibodies using an enzyme-linked immunosorbent assay. The overall prevalence of anti-HAV antibodies was 64.4% (1142/1173). While the rate of sero-positivity was over 80% in the 5–9 age group and more than 90% after 14 years of age in south-eastern and eastern regions, it was lower than 50% at the age of 5–9 years in central and western regions and remains under 80% in those areas. We conclude that the differences observed in HAV sero-positivity among various geographical regions in Turkey support a universal HAV immunization policy for children currently living in regions of intermediate endemicity.     

Prevalence of anti-hepatitis A antibodies in an urban middle class area of Argentina: some associated factors.

OBJECTIVE: This study evaluated the seroprevalence of hepatitis A virus (HAV) antibodies in 360 middle-class subjects from Buenos Aires City and its outskirts. METHODS: The study population included 360 individuals between 10 and 89 years of age, from the socioeconomic middle class in Buenos Aires City and some suburban areas of Buenos Aires province. Antibodies to hepatitis A virus were determined by enzyme immunoassay test kits. RESULTS: The overall prevalence of HAV antibodies was 42.2%. The highest percentage of seronegativity was found in the subgroup of younger people without a history of symptomatic hepatitis and living in houses with more than one bathroom (86.9%). In the subgroup aged 21 to 60 years, the highest rates of seronegativity were found in individuals with higher level of education living in houses with tap water (66.6%). In both groups, seronegativity may be correlated with a higher socioeconomic status. CONCLUSIONS: In the middle-class community studied, more than 50% of people under 30 years of age were unprotected against HAV. Thus, the use of a vaccine against hepatitis A has to be considered for the prevention of symptomatic hepatitis, especially in adults at risk of infection, such as those who travel to areas with poor sanitation, taking into consideration that the severity of the disease increases with age.     

Hepatitis A: Epidemiology and prevention in developing countries

Hepatitis A is the most common form of acute viral hepatitis in the world.Major geographical differences in endemicity of hepatitis A are closely related to hygienic and sanitary conditions and other indicators of the level of socioeconomic development.The anti-hepatitis A virus(HAV)seroprevalence rate is presently decreasing in many parts of the world,but in less developed regions and in several developing countries,HAV infection is still very common in the first years of life and seroprev-alence rates approach 100%.In areas of intermediate endemicity,the delay in the exposure to the virus has generated a huge number of susceptible adolescents and adults and significantly increased the average age at infection.As the severity of disease increases with age,this has led to outbreaks of hepatitis A.Several factors contribute to the decline of the infection rate,including rising socioeconomic levels,increased access to clean water and the availability of a hepatitis A vaccine that was developed in the 1990s.For populations with a high proportion of susceptible adults,implementing vaccination programs may be considered.In this report,we review available epidemiological data and implementation of vaccination strategies,particularly focusing on developing countries.     

Seroepidemiology of hepatitis A virus infection among school children in Delhi and north Indian patients with chronic liver disease: implications for HAV vaccination

BACKGROUND: Universal vaccination against hepatitis A virus (HAV) has been recommended for children because of the changing epidemiological pattern of HAV. Vaccination has also been advised for patients with chronic liver disease as HAV superinfection in these patients can result in severe or even fatal disease. In India, the indications for HAV vaccination are not clear due to contradictory seroepidemiological data in children and lack of data on HAV seroprevalence in patients with chronic liver disease. METHODS: Sera were collected from children studying in two government-run schools and from patients with chronic liver disease attending the Liver Clinic at the All India Institute of Medical Sciences (AIIMS). The sera were tested for anti-HAV antibodies. The incidence of HAV-induced acute hepatitis and acute liver failure at AIIMS over the last 10 years was also assessed. RESULTS: A total of 93.2% (1328/1424) of the school children between 4-18 years of age who were included in the study had anti-HAV antibody in their sera. Eighty percent of the children had antibodies against HAV in their sera by the age of 5 years, whereas all the children above 16 years were positive for anti-HAV antibody. A total of 256 patients with chronic liver disease (94 with cirrhosis of the liver, 160 with chronic hepatitis) were tested for the presence of anti-HAV antibody. Of them, 97.6% (248/254) had anti-HAV antibody in their sera. The annual frequency of HAV-induced acute viral hepatitis and acute liver failure at AIIMS during the last 10 years did not show any change. CONCLUSION: Mass vaccination against HAV is not required in north India because of the presence of protective antibodies against HAV in the majority of the population.     

Changing pattern of hepatitis a virus epidemiology in an area of high endemicity

Background

Continuous assessment of hepatitis A virus (HAV) seroepidemiology is a useful tool to control the risk of infection.

Objectives

This study aimed to evaluate the changing patterns of anti-HAV seroprevalence in a population,which isgenerally considered to be anarea ofhigh endemicity.

Patients and Methods

Overall, the results of 3349 sera collected during the period 2005-2008 from patients attending the University Hospital of Cagliari, Italy were studied; their mean age was 52.7 years, (s + 16.22). Patients with liver disease were excluded from the study. Age specific seroprevalence results were compared with those observed in similar previous studies carried out in the same area.

Results

The overall prevalence of anti-HAV was 74.6% with consistently lower values in subjects younger than 40 years (17.5%; P < 0.0001) particularly in those under 30 years of age (8.9%, CI 5.8-11.9). A significant declining trend in age specific seroprevalence has been foundin people under 30 years;61% in 1988, 33% in 1995 and 8.9% in 2005-2008.

Conclusions

Our findings show that a significant decline inherd immunity has occurred in the last 20 years as a consequence of lower HAV circulation due to improvementsin socio-economical and hygienic conditions. Adolescents and young adults are becoming increasingly susceptible to HAV infections, as recent outbreaks of acute HAV hepatitis have occurred. Persistent environmental monitoring and the implementation of prevention measures must be considered in order to contain the risk related to this epidemiological shift.     

Investigations of the epidemiology of infections with hepatitis A virus in Jamaica

Between January 1995 and August 1998, a study was conducted to elucidate the epidemiology of hepatitis A virus (HAV) in Jamaica. Participants were recruited from six sites across the island. The potential risk factors for transmission which were studied included age of the individual, gender, residence (urban v. rural area), sanitary facilities (flush toilet v. pit) and source of domestic water (indoor plumbing v. other). There were 128 male subjects and 211 female, aged 3-90 years. The mean ages of the males and females were 24.9 and 25.6 years, respectively. The seroprevalence of HAV in the study population, estimated by ELISA, was 59.9%. Logistic regression indicated that age (P < 0.001) and source of domestic water (P = 0.006) were the major contributors to exposure to HAV. The rate of exposure to the virus was seen to increase with age. By the age of 10 years, 30% of children had been exposed, and almost 100% of the oldest subjects were seropositive. Rates of exposure to HAV were higher among households which had external sources of water, including standpipes, rivers and tanks, than those with indoor plumbing. Although the seroprevalence of HAV in Jamaica is similar to that seen in developing countries, the age-related pattern of exposure mirrors the pattern seen in developed countries.     

Seroepidemiology of hepatitis A infection in India: changing pattern.

OBJECTIVE: Recent changes in the epidemiology of hepatitis A virus (HAV) infection and the availability of effective vaccines have renewed interest in this infection. We determined the age-related prevalence of anti-HAV antibodies in India and looked for differences by known risk factors for HAV infection. METHODS: In this prospective study, serum samples obtained from 1612 subjects aged 1 to 60 at six centers in five cities (Calcutta, Cochin, Indore, Jaipur and Patna) during the period February to August 1998 were tested for anti-HAV antibodies. Demographic and socio-economic information was obtained by questionnaire. RESULTS: The overall seroprevalence rate was 65.9%, varying from 26.2% to 85.3% in various cities; there was no difference between males and females. Seropositivity increased with age from 52.2% in the 1-5 year age group to 80.8% in those aged 16 years or more. Seroprevalence rates were significantly lower in those aged 1-5 years compared with other age groups (p<0.0001). There was no difference in seroprevalence between those with monthly family income Rs 5001. Multivariate analysis showed that anti-HAV seroprevalence varied significantly by source of water supply, being highest when the supply was municipal. CONCLUSION: Our results indicate an epidemiological pattern of intermediate endemicity. This finding has public health implications as it indicates that a significant proportion of the Indian adolescent and adult population is at risk of HAV infection.     

Association between seropositivity of antibodies against hepatitis a virus and Helicobacter pylori

Helicobacter pylori and hepatitis A virus (HAV) are documented to share common transmission routes including fecal-oral. This study examined the association between seropositivity of antibodies against H. pylori (anti-HP) and HAV (anti-HAV) via a community-based survey of 40 randomly selected kindergartens in 10 urban and 10 rural areas. Serum samples from 2,047 healthy preschool children and 104 teachers were screened for anti-HP by enzyme-linked immunosorbent assay, and for anti-HAV by microparticle enzyme immunoassay. In children, a low prevalence of anti-HAV (0.44%) was found, in contrast to a high prevalence in their teachers (78.8%); anti-HP seroprevalence was 6.4% for children and 30.8% for teachers. Anti-HAV and anti-HP seropositivities were significantly associated in teachers after adjustment for age, sex, and residential area through multiple logistic regression analysis (multivariate-adjusted odds ratio = 7.3; 95% confidence interval [CI] = 1.4-36.8, P < 0.001). Our findings suggest that HAV and H. pylori may have shared transmission routes in central Taiwan 15 years or more ago, but not any recently.     

Association between hepatitis A virus and Helicobacter pylori in a developing country: the saga continues

BACKGROUND: The epidemiologic association between Helicobacter pylori and hepatitis A virus (HAV) has been evaluated by various different groups with conflicting conclusions. The aim of the present study was to determine the prevalence of HAV and H. pylori infection among adolescents attending high schools in Lebanon, and to identify the sociodemographic factors associated with their prevalence, individually and concurrently. METHODS: Nine hundred and two school students 14-18 years of age were selected randomly from 30 schools scattered all over Lebanon and tested for IgG antibodies against hepatitis A and H. pylori. Each student received a copy of a self-administered questionnaire to be completed by his/her parents inquiring about demographics, history of immunization, and prior viral hepatitis illness in the student. Bivariate analysis examined the association between different sociodemographic variables and prior HAV or H. pylori infection, and multivariate regression analysis was done to determine the factors independently associated with prior infection. RESULTS: Using ELISA the seroprevalence of antibodies against HAV was 71.3% as compared to 61.6% for anti-H. pylori. A total of 9.1% of those tested were negative for both agents. A multinomial regression analysis revealed that place of residence in relation to district or urban versus rural areas, in addition to mothers' education, were important determinants for the incidence of both agents. CONCLUSION: The low number of subjects negative for both H. pylori and HAV antibodies in Lebanon is indicative of their high prevalence in the country. It is possible that this high prevalence reflects an age-specific prevalence rather than a true association.     

Increasing trend of acute hepatitis A in north India: need for identification of high-risk population for vaccination

BACKGROUND AND AIMS: Hepatitis A (HAV) is endemic in India and most of the population is infected asymptomatically in early childhood with lifelong immunity. Because of altered epidemiology and decreasing endemicity, the pattern of acute HAV infection is changing from asymptomatic childhood infection to an increased incidence of symptomatic disease in the 18-40 age group. The aims of the present study were to assess whether the proportion of adults with acute HAV infection has been increasing over the years and to analyze the seroprevalence of immunoglobulin G (IgG) anti-HAV antibodies in young adults above the age of 15 years as well as in cases of chronic liver disease. METHODS: Sera collected from 3495 patients with acute (1932) and chronic (1563) liver disease attending the Medical Outpatient Department of Lok Nayak Hospital during the previous five years (1999-2003) were tested for various serological markers of acute (HBsAg, HBcIgM, anti-HCV, HEV-IgM, and HAV-IgM) and chronic (HBsAg, HBcIgG, HBeAg, and anti-HCV) hepatitis. In addition, 500 normal healthy attendants of the patients above the age of 15 years were tested for IgG anti-HAV as controls. RESULTS: Of 1932 patients with acute viral hepatitis, 221 (11.4%) were positive for immunoglobulin M (IgM) anti-HAV. The patients who were IgM anti-HAV negative included hepatitis B (321 patients), C (39 patients), E (507 patients) and unclassified (844 patients). Although the frequency of HAV infection among children had increased (10.6% to 22.0%) in the 5-year period, the frequency of HAV infection among adults had also increased (3.4% to 12.3%) during the same period. A total of 300 patients with chronic liver diseases that were etiologically related to hepatitis B (169), C (73) or dual infection (10) and alcoholic liver injury (48) were tested for the presence of IgG anti-HAV antibody; 98% (294/300) were positive for the antibody. CONCLUSIONS: Although universal vaccination against HAV is not currently indicated, selective vaccination of the high-risk population, based on their serological evidence of HAV antibody, would be a rational and cost-effective approach.     

Anti-hepatitis A virus seroprevalence among patients with chronic viral liver disease in Korea

BACKGROUND/OBJECTIVE: It is generally recommended that patients with chronic viral hepatitis should be vaccinated against hepatitis A virus (HAV) infection. We intended to evaluate the prevalence of IgG anti-HAV according to age in patients chronically infected with hepatitis B virus or hepatitis C virus in Korea. METHODS: From June to October 2006, 303 patients (226 male, 77 female) with chronic hepatitis, liver cirrhosis, or hepatocellular carcinoma were recruited (mean age 50.8+/-14.4 years; range 16-84). The sera were tested for antibodies to HAV, and overall and age-specific seroprevalence of anti-HAV was assessed. RESULTS: Hepatitis B virus infection was the etiology of liver diseases in 267 patients (88.1%), with hepatitis C virus infection in 36 (11.9%). The distribution of clinical diagnosis was chronic hepatitis in 86 patients (28.4%), liver cirrhosis in 36 (11.9%), and hepatocellular carcinoma in 181 (57.9%). The patients were categorized by decade of age and the distribution was as follows: nine patients (2.5%) in their teens, 23 (6.2%) in their 20s, 36 (12.4%) in their 30s, 78 (25.7%) in their 40s, 72 (24.1%) in their 50s, and 85 (29%) >or=61 years. The overall seroprevalence of anti-HAV was 87.8% (266/303), and no difference was observed in sex (86.7 vs. 90.9%, P=0.42). The seroprevalence in each age group was 22.2, 26.1, 72.2, 97.4, 100 and 98.8%, respectively, showing marked increase in those over 40 years of age (P<0.001). CONCLUSION: Our study demonstrates that most Korean patients over 40 years of age with chronic liver disease have already been exposed to HAV.     

Seroprevalence study of hepatitis A virus in Fars province, southern Iran

Background

There are several studies on seroprevalence of hepatitis A virus (HAV) in adults in the Middle East.

Objectives

To determine seroprevalence of HAV among adult population in Fars province, southern Iran.

Patients and Methods

In a cross-sectional study, we checked anti-HAV antibody (IgG) in subjects refereed to our health care centers to perform laboratory tests before getting married between March 2008 and March 2009. Age-specific seroprevalence was also determined. Some risk factors like level of education, type of residence, job, numbers of family members, and access to treated water were also evaluated in these participants.

Results

From 1050 subjects studied, 927 (88.2%) had ant-HAV antibody; 123 (11.8%) were antibody negative. Among subjects aged < 20 years, the anti-HAV seroprevalence was the lowest (79.3%) followed by subjects aged 20-30 years (91.3%) and those > 30 years (99%) (p = 0.01). 85.1% of studied individuals in urban areas had anti-HAV IgG while 95.9% of subjects in rural regions were anti-HAV positive (p = 0.001). The seroprevalence of HAV antibody was significantly associated with number of family members (p = 0.001).

Conclusion

HAV is highly prevalent in our region especially in rural areas. It is better to vaccinate the children for HAV by the time they receive HBV vaccine or when they are five years.     

Age-specific seroprevalence of anti-hepatitis a antibody among 1-30 years old population of savadkuh, mazandaran, iran with literature review

Background

To determine age-specific seroprevalence rates of hepatitis A virus (HAV) immunoglobulin G (IgG) antibody in Savadkuh district, Mazandaran province, north of Iran, as well as to compare the collected data with earlier seroprevalence studies in the region and Iran in order to draw a proper epidemiological pattern for HAV infection in the country.

Objectives

This study aimed to assess an age-specific HAV seroprevalence among 1- to 30-yearold people in Savadkuh, a less developed district of Mazandaran province, north of Iran.

Patients and Methods

The study participants were 984 subjects who aged from one to 30 years and were residents of rural and urban areas of Savadkuh. They were selected using cluster sampling method and divided into five age groups: 1-2.9 (316 cases), 3-6.9 (254 cases), 7-10.9 (201 cases), 11-17.9 (115 cases), and 18-30 (98 cases). Anti-HAV antibody was measured by ELISA method. Seroprevalence rates among different age groups and their relationship to residency, educational levels of parents, water supply, and waste water disposal system was analyzed using chi-squared test.

Results

Overall seroprevalence rate was 19.20 % with no significant difference between rural and urban residents. The seroprevalence rates increased significantly with age: from 5.7 % in age group 1-2.9 year to 34.8 % in adolescents, and to 68.4 % among young adults (P < 0.0001); regardless of significant differences in educational levels among parents of residents in two areas it did not affect seroprevalence rates. Findings of this study and reviewing other reports from the region and the country suggest an epidemiological shift towards lower rates of anti-HAV antibody seroprevalence.

Conclusions

It appears that anti-HAV antibody seroprevalence rate has been declining among Iranians and thereby more children would be susceptible to this infection. This would necessitate revising current strategies of preventative measures in Mazandaran and Iran.