Sample size calculation was performed based on a prevalence of 0.20 % with 0.025 precision and 95 % confidence interval which yielded a total 983 individuals. 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 Il17a supply, and waste water disposal system was analyzed using chi-squared test. Results Overall seroprevalence rate was 19.20 % with no signi?cant difference between rural and urban residents. The seroprevalence rates improved signi?cantly 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 signi?cant differences in educational levels among parents of residents in two areas it did not affect seroprevalence rates. Findings of this study and critiquing 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 therefore more children would be susceptible to this illness. This would necessitate revising current strategies of preventative measures in Mazandaran and Iran. strong class=”kwd-title” Keywords: Hepatitis A Computer virus, Antibodies, Seroprevalence, Iran 1. Background Hepatitis A computer virus (HAV) is an enterically- transmitted illness and leading cause of acute viral hepatitis throughout the world . Epidemiologically, numerous geographical distribution of HAV illness is present that correlates closely with hygienic and sanitary conditions and other development indicators . Clinical manifestation of HAV illness is definitely highly age dependent and is minimal in children . Children play an important part in HAV transmission. Distribution of anti-HAV antibody seroprevalence over age groups can be used like a marker for HAV epidemiologic pattern and viral transmission through a community . Declining seroprevalence rate in a populace, particularly in children, is an indication to reduced incidence of HAV . Many seroepidemiological findings revealed that a transition to lower rates of illness occurred in many hyperendemic countries within past two decades where their economic status improved . In this situation, medical manifestation of hepatitis A is likely to become a more serious problem in these countries. HAV illness could be prevented by immunization, and HAV vaccine may be used for pre-and post-exposure prophylaxis. Cost and feasibility are VX-680 (MK-0457, Tozasertib) two major barriers to implementing HAV vaccination programs in these countries. Types of preventative strategies depend on epidemiologic characteristics of HAV illness and additional vaccine-preventable diseases in any VX-680 (MK-0457, Tozasertib) given country . In Iran, no appropriate periodic and age-specific seroprevalence data are available nationwide and precise epidemiological characteristics of HAV illness are unfamiliar. Results of earlier seroprevalence studies on different populations in the country suggested a hyperendemic pattern . However, data collected in some recent studies shown lower rates of illness especially among children . 2. Objectives This study targeted to assess an age-specific HAV seroprevalence among 1- to 30-year-old populace in Savadkuh, a less developed area of Mazandaran province, north of Iran. Also, in order to determine epidemiological characteristics of HAV illness in Mazandaran and over the country and to strategy the most appropriate preventative strategies, relevant content articles previously issued in Iran were examined. 3. Individuals and Methods This cross-sectional seroepidemiological study was carried out in Savadkuh area, Mazandaran province, north of Iran. Savadkuh is definitely a less developed mountainous part of Mazandaran with 70,000 inhabitants, equally distributed between rural and urban areas. Its population denseness is 33/km(2) compared to 140/km(2) in Sari area, the capital of province. A river passes through almost all parts of the area. Take action of agriculture is the main occupation of occupants. In four areas, urbanization infrastructures were motivated and more people relocated to these areas known as city of Savadkuh. Target population consisted of healthy 1- to 30-year-old occupants of Savadkuh. Random cluster sampling was used to enroll required samples, which was proportional to the number of inhabitants in each area. Sample size calculation was performed based on a prevalence of 0.20 % with 0.025 precision and 95 % confidence interval which yielded a total 983 individuals. Epidemiologic data were collected from a questionnaire including VX-680 (MK-0457, Tozasertib) age, sex, place of residence, educational levels of parents and adults, source of water supply, and method of waste water and sewage disposal. Based on education levels of adults and parents,.