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although hepatitis a virus ( hav ) infection is a self - limited disease , the infection in adults causes significant morbidity , resulting in long absences from work for several weeks , possible hospitalization , and occasional mortality resulting from acute fulminant hepatitis ( 1 , 2 ) .
infection rates have declined with better hygiene practice and public sanitation , but remain heterogeneous across geographic and socioeconomic strata ( 1 , 2 ) .
hepatitis a has become a major cause of acute viral hepatitis in young adults in korea since 1996 ( 3 - 7 ) .
korea seems to be a country in transition from a high to low endemic region and faces the paradox of increasing disease burden with decreasing disease incidence .
the current national immunization guide recommends hav vaccination for individuals at increased risk of infection or its complications ( 3 , 4 ) .
the guide also states that a universal immunization program should be considered , but further discussion is needed ( 3 , 4 ) .
korea , has a draft system , and the military has been especially vigilant for viral hepatitis , since active disease not only impairs an individual 's military readiness , but also can threaten a large number of troops .
military personnel are considered to have a higher risk for hepatitis a than the civilian population ( 8) . however , there are no data available regarding hav infection in korean military personnel .
thus , the goal of this study was to determine the incidence rate and the prevalence of antibody to hepatitis a in young soldiers in the republic of korea ( rok ) army .
the database of the armed forces medical command ( defense medical information system ; demis ) was reviewed to identify the number of hepatitis a cases reported . in the rok army , it is mandatory to report individual cases of communicable diseases , including viral hepatitis , to the department of preventive medicine in the armed forces medical command ( 9 ) .
we analyzed the data of hepatitis a cases that had been submitted from january 2000 to december 2004 .
the annual incidence rate was defined as cases per 100,000 persons per year among approximately 500,000 soldiers .
the cases were defined as epidemic cases when more than two cases had occurred in the same military unit within a 4-week period .
we retreived data from electronic medical records ( demis ) and obtained baseline demographic and clinical information , including age , gender , clinical symptoms , and laboratory findings .
in addition , we planned an additional study in order to evaluate the seroprevalence of hav infection .
serum samples were obtained from randomly selected subjects among those who had been admitted to the armed forces capital hospital from september 2005 to february 2006 .
patients who are over 25 yr old , chronic disease cases , viral hepatitis cases , and females were excluded .
we , therefore , planned to obtain a specific study group that included healthy young military personnel .
anti - hav igg and anti - hbs igg antibodies were measured by axsym ( abbott laboratories , wiesbaden , germany ) .
the test was performed in an automated format , and cut - off values were established according to the instructions by the manufacturer .
a total of 147 cases of hepatitis a were reported in young korean soldiers from january 2000 through december 2004 . of these , 64 ( 43.5% ) cases were reported as epidemic cases , and the remaining 83 ( 56.5% ) were reported as sporadic cases ( table 1 ) .
the mean annual incidence of hepatitis a was 5.9 per 100,000 persons , based on the cases reported among approximately 500,000 soldiers .
the annual incidence rates were 7.4 per 100,000 persons in 2000 , 1.6 in 2001 , 4.4 in 2002 , 9.8 in 2003 , and 6.2 in 2004 .
a total of 111 male patients with acute hepatitis a were analyzed and their median age was 21 yr old ( range , 19 to 27 yr ) .
the remaining 36 cases were excluded from the analysis since the medical records were unavailable .
table 2 shows clinical characteristics and initial laboratory findings of patients with acute hepatitis a in the military personnel of korea .
the most common symptom was nausea ( 86.5% ) , and all patients had recovered without complications .
a total of 200 subjects were enrolled in the study to analyze anti - hav immune status .
all patients were male with a median age of 21 yr ( range , 19 - 24 ) .
the overall anti - hav igg seropositive rate was 2% ( 4/200 , 95% ci , 0.60 - 5.21% ) . the prevalence of anti - hbs igg was detected as 72.9% ( 146/200 , 95% ci , 66.44 - 78.69% ) .
in this study of hav infections among korean soldiers , the data suggested that the annual incidence of hepatitis a was approximately 6 per 100,000 persons .
the cases of hepatitis a reported have sustained steadily over the past 5 yr , and 11 outbreaks in the military personnel have been reported .
an anti - hav igg seropositivity of 2% in our study was lower than those reported in these age groups in other developing countries ( 2 , 10 ) .
in korea , the incidence and seroprevalence of hepatitis a in military personnel have not been previously available .
it is necessary to know the exact number of new cases in order to place the prevalence of hav infections in a proper perspective and establish a realistic control program . to the best of our knowledge ,
this is the first study on the extent of hav infections among young soldiers in rok army which has a draft system . in the past ,
hepatitis a epidemics were mainly related to the overcrowding and lack of hygienic sanitary conditions typical for military life .
in addition , most papers reporting hepatitis a epidemics in the forces were published before 1990 ( 8) .
almost all of the studies published thereafter discussed the efficacy of the vaccine and suggest different vaccination schedules for the militaries , taking it for granted that they were a high - risk group and need prophylaxis ( 8) .
militaries are considered just as a sample of the general population in most papers , in which a decrease in seroprevalence was generally found for all population groups in recent years .
in fact , a recent paper reported a hepatitis a incidence rate in militaries similar to that found in the general population ( 11 ) .
now , due to the improvement of the sanitation level , the risk is mainly ascribed to travels to high endemicity areas . among korean civilians ,
the overall seropositivity rate of hav igg in subjects under 20 yr of age was 63.8% in 1979 and 50.3% in 1989 , followed by a rapid decline to 11.7% in 1995 , and 4.6% in 1996 ( 3 ) .
the results of epidemiologic studies including our data indicate that korea is in transition from a high- to low - endemicity region ( 3 , 6 ) .
the seroprevalence of hav infection in young korean soldiers was approximately 2% , comparable to that in low endemicity countries ( 12 ) .
the low rate of natural infection clearly indicates that a large part of the younger population is susceptible to hav infection with the potential for large - scale outbreaks , unless they acquire proper immunity .
food - born or water - born outbreaks in susceptible people may become a problem in the future . the strong evidence for the decreasing incidence of hav infection as a result of improved personal hygiene and living conditions , supported by the economic growth , will increase the risk of future outbreaks ( 8 , 10 ) .
inactivated hepatitis a vaccine has been available since 1997 in korea ( 3 , 4 ) . the vaccine is recommended for use in people including children who are at increased risk of infection ( 3 , 4 ) . however , immunization with hepatitis a vaccine is not recommended in healthy young adults as part of a routine immunization schedule . since 1996
, several outbreaks of hepatitis a in young adults and school children have indicated that there is a need for active immunization in adolescents and young adults at increased risk , such as military personnel . as suggested by sohn et al .
, korea requires an evaluation of the cost - effectiveness of implementing a routine schedule of hav immunization in children ( 3 ) .
the evaluation of the cost - effectiveness of routine immunization of hav in korean military personnel is also warranted . for hepatitis b immunization ,
a cost - effectiveness study was conducted by military investigators , who concluded that screening for hepatitis b immunity was cost - effective when the prevalence of immunity was > 12% in new military recruits ( 13 ) .
when considering hav immunization for young korean soldiers , our data suggest that the routine screening for hepatitis a immunity may not be cost - effective .
patient with minor symptoms were not included in the data if they did not seek medical attention or if they were not reported . in conclusion
, we described a population - based study of the epidemiology of hav infections among the military personnel of korea , and the overall hav seroprevalence was approximately 2% .
given the changing epidemiology of the disease and the associated increase in morbidity , it is suggested that the routine hav vaccination of korean military personnel might be mandatory .
this study was performed to determine the incidence and seroprevalence of hepatitis a virus ( hav ) infections in young soldiers in the republic of korea army . from january 2000 through december 2004 , a total of 147 hepatitis a cases were reported to the armed forces medical command . 
 the annual incidence rates were 7.4 per 100,000 persons in 2000 , 1.6 in 2001 , 4.4 in 2002 , 9.8 in 2003 , and 6.2 in 2004 , based on the reported cases among approximately 500,000 soldiers . 
 all patients were males with a median age of 21 yr ( range , 19 - 27 ) . 
 the most common symptom was nausea ( 86.5% ) , and all patients had recovered without complications . in addition , in order to evaluate the seroprevalence of hav infection in young adults , serum samples were obtained from randomly selected young subjects among those who had been admitted to the armed forces capital hospital from september 2005 to february 2006 . 
 a total of 200 subjects were enrolled in the study to analyze the anti - hav immune status . 
 the overall anti - hav igg seropositive rate was 2% ( 4/200 , 95% ci , 0.60 - 5.21% ) . given the changing epidemiology of the disease and the associated increase in morbidity , it was suggested that the routine hav vaccination for korean military personnel might be necessary .