Epidemiology of Hepatitis A: Past and Current Trends

Abstract

Hepatitis A virus is a common infectious etiology of acute hepatitis worldwide. It was not until World War II (1973) when hepatitis A virus was first identified by an American virologist, Stephen Mark Feinstone. The virus is most commonly transmitted through contaminated food, water, or sexual contact (oral-anal sex). The discovery of hepatitis A virus vaccine is considered a milestone in the history of acute viral hepatitis. Hepatitis A occurs worldwide and frequent outbreaks have been reported over the years. Major geographic differences have existed in endemicity of the disease depending primarily upon hygiene and sanitation practices. Some countries have experienced shifting of endemicity due to improvement of environmental hygiene, swelled International travel and national recommendations for hepatitis A vaccination. The age of acquiring hepatitis A virus is also shifting toward adolescents and adults. This has led to a more symptomatic disease, since hepatitis A infection among children is usually asymptomatic; this is known as the paradox of Hepatitis A epidemiology.

Hepatitis A Outbreak in a Facility for the Disabled, Gyeonggi Province, Korea: An Epidemiological Investigation

“…According to the laboratory test results, groundwater was suspected to be the source of the outbreak, but this hypothesis was not confirmed due to a lack of information that clarified the temporal order of groundwater contamination and the HAV outbreak. Considering that the incubation period of HAV infection extends up to 50 days [1,[7][8][9], the epidemic curve of this outbreak (Figure 1) showed a point source outbreak pattern. The overall attack rate at facili- ty A was 14.3%, with the highest attack rate (43.8%) among individuals aged 31-40 years, which is consistent with previous studies finding that younger adults are more vulnerable to HAV infection [10,[17][18][19].…”

“…Therefore, an epidemiological investigation was initiated to determine the size and source of infection and prevent further transmission. Since HAV infection can be transmitted by contaminated food or feces, it is crucial to rapidly find and block the source of infection [1,9].…”

“…There are 7 genotypes of HAV, 4 of which (I, II, III, IV) induce infection in the hu-pISSN 1975-8375 eISSN 2233-4521 man body [1][2][3]5,6]. HAV is transmitted by contaminated food or water and has an average incubation period of 28 days (range, 15-50) [1,[7][8][9]. The clinical symptoms of HAV vary from mild to severe, and in symptomatic cases, dark urine and jaundice appear rapidly after the initial manifestation of systemic symptoms such as fever, headache, and fatigue [8,10].…”

Tracking the Epidemiologic Shifts in Hepatitis A Sero-Prevalence Using Age Stratification: A Cross-Sectional Study at Jordan University Hospital

“…The first approach relies on determining the prevalence in the entire population, while the second utilizes an age-specific approach [ 19 ]. For the former method, the endemicity of HAV is classified into a high level if the prevalence exceeds 50% of the population, intermediate endemicity (prevalence of 15–50%), and low endemicity if the prevalence is less than 15% in the studied population [ 19 , 20 ]. The later approach classifies endemicity as follows: high (≥90% by age 10 years), intermediate (≥50% by age 15 years, with <90% by age 10 years), low (≥50% by age 30 years, with <50% by age 15 years), and very low (<50% by age 30 years) [ 21 ].…”

“…Based on the aforementioned points, the concept of “the paradox of HAV epidemiology” can be easily fathomable. This concept describes the paradoxical relationship between HAV endemicity and burden of the disease [ 18 , 20 ]. High HAV endemicity indicates the occurrence of infection in early childhood, which is associated with a low burden of hepatitis A.…”