Acute Hepatitis in the U.S. —A Success Story, But the Game Isn't Over

Abstract & Commentary

By Stan Deresinski, MD, FACP, Clinical Professor of Medicine, Stanford, Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center, is Editor for Infectious Disease Alert.

Source: Centers for Disease Control and Prevention. Surveillance for acute hepatitis - United States, 2005. Surveillance Summaries. MMWR 2007; 56(No. SS-3):1-24. www.cdc.gov

Synopsis: There have been dramatic decreases in the reported cases of acute hepatitis due to hepatitis viruses A, B and C in the U.S.

The incidence of acute Hepatitis A, which has previously cycled at 10 to 15 year intervals, has steadily decreased since its last peak in 1995, reaching a nadir in 2005 when 4488 cases were reported. The incidence in 2005, 1.5 per 100,000 population, was the lowest ever reported and, in fact, was more than 80% lower than that observed at the previously recorded cycle nadir. The most frequently identified risk factor was international travel, accounting for 15% of cases, with most associated with travel in Mexico, Central and South America. Sexual and household contact with another individual acutely infected with hepatitis A virus accounted or 12% of cases.

The onset of the decrease in incidence of acute hepatitis A (Figure 1) infections coincides with the introduction of hepatitis A vaccines in 1995 and the issuance of public health recommendations for their use in the following year. More dramatic decreases occurred after implementation of childhood vaccination recommendations made in 1999. Not all states implemented vaccination programs and, in 2005, approximately two-thirds of cases arose in states without childhood vaccination recommendations. At the end of 2005, recommendations were made that all children aged 12 to 23 months be vaccinated.

The incidence of acute hepatitis B infection in 2005, 1.8 cases per 100,000 population, was the lowest ever reported. This represented a total of 5494 reported cases, but taking into account the asymptomatic nature of many infections and underreporting, it was estimated 51,000 cases had occurred in 2005. Approximately one-third reported a sexual risk factor; 9.3% reported undergoing surgery 6 weeks to 6 months before the onset of illness.

The decrease in incidence of acute hepatitis B infection (Figure 2) began during the middle of the 1980s and coincided with the implementation, in steps, of a comprehensive national prevention strategy. This consisted of universal infant vaccination, routine screening of pregnant women and administration of immunoprophylaxis of at-risk infants, routine vaccination of children and adolescents not previously vaccinated, and vaccination of at-risk adults. The last include healthcare workers, dialysis patients, household and sexual contacts, individuals with multiple sexual partners or a sexually transmitted disease, men who have sex with men, injection drug users, and recipients of certain blood products.

Only 671 cases of acute hepatitis C infection were reported in 2005, for an incidence of 0.2 per 100,000 population. Taking into account missed diagnoses of asymptomatic cases and underreporting, it was estimated, however, that 20,000 new infections had occurred. Injection drug use accounted for 50% of cases; 14% reported having had surgery, 23% had had multiple sex partners, and 8% reported occupational exposure to blood.

The incidence of reported acute hepatitis C infections peaked in the late 1980s and has declined since. (Figure 3) While in 2005, the most commonly identified risk factor remained injection drug use, the overall decrease in incidence was due in large part to a decrease in cases among that group. The second most frequently reported risk factor was having multiple sexual partners. Transfusion was rarely identified as a risk factor.

Overall, these results illustrate the results of a remarkably successful public health program in the prevention of viral hepatitis in the U.S. - but there is still a long way to go.