One of the world’s experts on the epidemiology and natural history of viral hepatitis, Dr. Leonard Seeff is the Chief of Gastroenterology at the Georgetown University School of Medicine in Washington. In addressing these topics as they relate to hepatitis C virus (HCV), Dr. Seeff discussed the difficulties in studying the natural history of an infection which is seldom detected in the acute stage, except in prospective studies of postransfusion hepatitis. Chronic hepatitis C first becomes clinically apparent 20 or 30 years later.
Despite these difficulties, a number of facts are known about the current epidemiology of HCV infection. One striking fact is that the annual incidence of acute hepatitis C has fallen in the United States from 180,000 cases a decade ago, to roughly 35,000 now – at the same time, the proportion of cases of acute hepatitis due to HCV has dropped from 21% to 14%. While the reasons for this marked decline are not definitely known, improved awareness of the dangers of sharing needles, elimination of blood donations from high-risk donors, and sensitive serological tests used in blood banks, are likely factors. Although HCV accounts for only a minority of cases of acute hepatitis, it is undoubtedly the most important cause of chronic hepatitis and liver disease. According to current NHANES surveillance data, the rate of seropositivity to anti-HCV in the general population is 1.8%.
The most common route of transmission is intravenous drug use. Currently, 43% of acute cases of hepatitis C are related to illicit drug use. Intravenous drug use is a highly efficient method of acquiring HCV infection, with 60% to 90% of current users being HCV-positive, many of them becoming so within months of beginning a drug habit. Drug transmission is not limited to intravenous needles; sharing of cocaine straws, in cocaine users who frequently have nasal erosions and ulcers, is becoming more common as a cause of HCV transmission. Transfusion-related acute hepatitis C is now very rare.
Among other possible modes of transmission is sexual transmission. This accounts for roughly 15% of acute cases, although the efficiency of sexual transmission is low, and infection is rare in long-term, steady partners. Perinatal transmission occurs in just five or six percent of infected monthers, more often if they are coinfected with HIV.
Breastfeeding is not thought to cause infection, and is considered safe. Other modes of transmission include contaminated equipment used in traditional or folk medicine, tattooing, body piercing, or sharing of personal items such as razors or toothbrushes.