Distribution of seroprevalence for Lop Buri and Narathiwat by age group.

<p>(A) anti-HEV IgG antibody and (B) anti-HAV IgG antibody prevalence in different age groups.</p

Comparison of socio-economic data between Lop Buri and Narathiwat.

<p>^aNational Statistical Office;</p><p>^bInformation Technology and Vocational Manpower Center;</p><p>^cLop Buri Governor’s Office;</p><p>^dLop Buri Provincial Public Health Office;</p><p>^eLopburi Provincial Livestock Office;</p><p>^fNarathiwat National Statistical Office;</p><p>^gNarathiwat Provincial Public Health Office;</p><p>^hNarathiwat Provincial Livestock Office.</p><p>Comparison of socio-economic data between Lop Buri and Narathiwat.</p

Geographical and population characteristics in the provinces of Lop Buri and Narathiwat.

<p>Map indicates the locations of Lop Buri and Narathiwat with information on their respective population density. The number of samples from individuals residing in each district is indicated on the map. Approximate pig population, pig farmers, and slaughter houses in each district are noted.</p

Previous studies of anti-HAV IgG prevalence in Thailand.

<p>Previous studies of anti-HAV IgG prevalence in Thailand.</p

Declining Trend of Hepatitis A Seroepidemiology in Association with Improved Public Health and Economic Status of Thailand

<div><p>Hepatitis A virus (HAV) is transmitted via the fecal-oral route from contaminated food or water. As part of the most recent survey of viral hepatitis burden in Thailand, we analyzed the current seroprevalence of HAV in the country and compared with data dating back to 1971. From March to October, 2014, a total of 4,260 individuals between one month and 71 years of age from different geographical regions (North = 961; Central = 1,125; Northeast = 1,109; South = 1,065) were screened for anti-HAV IgG antibody using an automated chemiluminescent microparticle immunoassay. Overall, 34.53% (1,471/4,260) possessed anti-HAV IgG antibody, and the age-standardized seroprevalence was 48.6%. Seroprevalence rates were 27.3% (North), 30.8% (Central), 33.8% (Northeast) and 45.8% (South) and were markedly lower than in the past studies especially among younger age groups. The overall trend showed an increase in the age by which 50% of the population were anti-HAV IgG antibody: 4.48 years (1971–1972), 6 (1976), 12.49 (1990), 36.02 (2004) and 42.03 (2014).This suggests that Thailand is transitioning from low to very low HAV endemicity. Lower prevalence of HAV correlated with improved healthcare system as measured by decreased infant mortality rate and improved national economy based on increased GDP per capita. The aging HAV immuno-naïve population may be rendered susceptible to potential HAV outbreaks similar to those in industrialized countries and may benefit from targeted vaccination of high-risk groups.</p></div

Correlation between infant mortality rate (per 1,000 live births), GDP, and age at which 50% of the population possessed anti-HAV antibody.

<p>Infant mortality rates (pink graphs), GDP per capita (blue graphs), and the mean age at 50% anti-HAV IgG positivity in the population (black line) are indicated. Half of the population around the mean age is denoted in gray areas.</p

Documented hepatitis A outbreaks in Thailand from 1984 to 2014.

<p>Circles denote outbreak events in different regions (North, purple; Central, blue; Northeast, green; South, yellow). Circle sizes correspond to the number of individuals affected. Outbreak in a calendar year is denoted as solid lines; those that continued to the following year are denoted in dashed lines. Line length corresponds to the recorded outbreak period.</p

The frequency of anti-HAV IgG positivity in each age group.

<p>Numbers above the line charts indicate the total seroprevalence for each age group.</p

Map of Thailand and the domicile of study participants.

<p>Seven provinces from the four regions (North, violet; Northeast, green; Central, blue; and South, yellow) are shown. Districts within a given province are denoted in different colors depending on the population density (range 0 to ≥ 601 individuals/km²). Number of study participants from each district is indicated.</p

Comparison of anti-HAV IgG positivity from 1971 to 2014.

<p>Seroprevalence data from this and other studies were plotted as line charts. The dotted line denotes 50% anti-HAV IgG positivity. Intersection with the seroprevalence curve indicates the mean age at which 50% of the individuals in the population possessed anti-HAV IgG (denoted by the numbers on the line graphs) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151304#pone.0151304.ref016" target="_blank">16</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151304#pone.0151304.ref018" target="_blank">18</a>].</p