![]() In most sub-Saharan African countries and other very low-income areas, the AMPI is less than 5 years ( Jacobsen and Wiersma 2010), which means that more than half of preschool-aged children have already contracted HAV and developed immunity as a result of their infection. The age at midpoint of population immunity (AMPI) is the youngest age at which half of the birth cohort has serologic evidence of prior exposure to HAV. Seroprevalence studies in low-income countries typically show that nearly 100% of older children and adults have anti-HAV immunoglobulin (Ig)G levels indicating prior infection with HAV and that the majority of young children already have serologic evidence of past infection ( Jacobsen 2009). However, even asymptomatic infections confer long-term immunity against HAV that can be detected with serologic tests. Surveillance for incident hepatitis A cases can be difficult in high-incidence areas because the majority of cases occur in young children who remain asymptomatic. Low-income countries typically have high HAV incidence rates. However, there are major differences in the profiles of countries with different socioeconomic profiles ( Jacobsen 2009). Globally, the HAV incidence rate is decreasing and the average age at infection is increasing ( Rein et al. Symptomatic hepatitis A patients typically miss several weeks of work or school, and the costs of medical care can be substantial ( Berge et al. Young children who are exposed to the virus usually have no symptoms of disease, but older children and adults often experience several weeks of jaundice and a lengthy convalescence, and they are at risk of acute liver failure and death. Tens of millions of individuals worldwide contract HAV through fecal–oral transmission each year, usually via ingestion of contaminated food or water or through contact with an infectious person ( Rein et al. This article summarizes the current epidemiology of hepatitis A in countries with different income levels and endemicity patterns, describes the major socioeconomic and environmental changes that are contributing to hepatitis A epidemiological transitions, examines the specific roles of international food trade and international travel on hepatitis A epidemiology, and uses globalization theory to predict the changes that are likely to occur in hepatitis A epidemiology over the next several decades. For infectious diseases generally, and for hepatitis A specifically, the globalization of trade and travel are important drivers of epidemiological change ( Suk et al. The globalization of economic markets and sociocultural practices is influencing human behaviors, altering the ways people interact socially and with the environment, and modifying the ways people conceive of health and seek health services ( Huynen et al. ![]() Evidence for globalization can be observed in the increasing rates of cross-border trade, the growing complexity of international supply chains, the rising pace of international travel and migration, and the social and cultural changes that are occurring as online communication makes it easy for people from different parts of the world to interact. Globalization is a process characterized by countries and people around the world becoming more interdependent and integrated across economic, political, cultural, and other domains.
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