The Incidence of Hepatitis A Infection
How Common is Hepatitis A Infection?
Hepatitis A is much more common in countries with underdeveloped sanitation systems and, thus, is a risk in most of the world. [11, 16] An increased transmission rate is seen in all countries other than the United States, Canada, Japan, Australia, New Zealand, and the countries of Western Europe.  Nevertheless, infections continue to occur in the United States, where approximately one-third of the population has been previously infected with HAV. [6, 12]
Each year, approximately 30,000 to 50,000 cases of hepatitis A occur in the United States. [5, 7] Historically, acute hepatitis A rates have varied cyclically, with nationwide increases every 10 to 15 years.  The national rate of HAV infections has declined steadily since the last peak in 1995. [5, 6] Although the national incidence—1.0 cases per 100,000 population—of hepatitis A was the lowest ever recorded in 2007, it is estimated that asymptomatic infections and underreporting kept the documented incidence-rate lower than it actually is. In fact, it is estimated that there were 25,000 new infections in 2007. [6, 22]
Although the rates of HAV infection have declined over the years, rates are twice as high among American Indians and Alaskan Natives.  Hispanics are also twice as likely to be infected compared to non-Hispanic Whites in the United States. . Rates among American Indians and Alaskan Natives have decreased dramatically, largely as a result of increased vaccination of children in both urban and rural communities. 
In 2007, the CDC reported a total of 2,979 acute symptomatic cases of hepatitis A.  Of these, information about food and water exposure was known for 1,047 cases, leading to an estimate that 6.5% of all infections were caused by exposure to contaminated water or food.  In 2,500 of the cases, no known risk factor was identified. 
Estimates of the annual costs (direct and indirect) of hepatitis A in the United States have ranged from $300 million to $488.8 million in 1997 dollars.  In one study conducted in Spokane, Washington, the combined direct and indirect costs for each case of hepatitis A from all sources ranged from $2892 to $3837. [2, 13] In a 2007 Ohio study, each case of HAV infection attributable to contaminated food was estimated to cost at least $10,000, including medical and other non-economic costs.  Nationwide, adults who become ill miss an average of 27 work-days per illness, and 11-to-22 percent of those infected are hospitalized. [6, 7] All of these costs are entirely preventable given the effectiveness of a vaccination in providing immunity from infection. [7, 13]