Posted: 14-Apr-2005 << BACK
Report from John Hopkins University, USA.
A new, long-term study of hepatitis c has found that once the virus is transmitted, it can take months for evidence of the virus to appear.1 This initial, acute phase can also be absent any symptoms. Thus, researchers at Johns Hopkins University are stressing the importance of more sensitive tests, like nucleic acid testing (NAT), which are designed to detect the virus' genetic material long before the immune system begins to respond with antibodies.2
According to estimates, nearly 4 million Americans (about 2 percent of the total population) are infected with hepatitis C, 2.7 million of whom have chronic infection. Most of the cases of HCV transmission in the U.S. are due to injection drug use.3 According to the authors of this study, more than two-thirds all cases of acquired HCV infection in the West are connected to illicit drug use. This occurs due to sharing needles or "works" when "shooting" drugs.3 Despite that fact, Andrea Cox, MD, PhD, an assistant professor of Medicine, and her colleagues wrote, "Prospective clinical data regarding the most common mode of HCV acquisition are rare, in part because acute-phase HCV infection is usually asymptomatic."
Evidence of Infection Can Develop Slowly
Based on that, Cox and her team prospectively evaluated the length of time before antibodies to the hepatitis C virus appear in a group of 179 initially infected injection drug users. The patients were enrolled from a larger, unrelated study on HCV incidence and risk factors. Despite counseling about the risks of injection drug use relative to HCV infection, about one-third of them eventually developed antibodies to their HCV infection at the start of the research, an "alarming" number, the investigators noted.
Each patient was interviewed at the beginning of the research about his or her drug use habits, and was classified from lowest to highest risk of contracting HCV. Those at highest risk were individuals who acknowledged daily injection drug use, as well as sharing drug paraphernalia.Each individual was then evaluated for evidence of HCV once per month throughout the study. Antibody testing was conducted to determine whether those who initially were antibody-negative had become positive. Those who had become antibody-positive then underwent testing to detect HCV RNA, a more sensitive analysis that looks for genetic material associated with the virus.
Antibodies May Take Months to Appear
After analyzing all the blood samples, Cox's group estimated the average time from initial infection to the appearance of antibodies was 36 days. However, in one case, antibodies were detected more than a year after infection. However, in no other case were antibodies discovered more than 63 days after HCV was initially contracted, they report.
The researchers also found that blood levels of a liver enzyme that suggest liver disease known as alanine aminotransferase (AL-uh-neen uh-mee-noh-TRANZ-fer-aze) (ALT) climbed four-fold, on average, once the virus was detected in these patients. Evidence of infection preceded increases in ALT in half of the patients and rises in total bilirubin levels in approximately three-quarters of the individuals. However, Cox's team learned that ALT levels were not closely linked with positive HCV RNA tests or in those with persistent viral infection, sex or race of an individual, or the outcome of infection. "That viremia frequently precedes ALT level elevation supports the hypothesis that HCV is not a hepatotoxic virus and that factors that come into effect later, such as immune response, are responsible," the research team wrote.
None of the individuals developed jaundice, confirming the notion that early, acute HCV infection usually lacks obvious symptoms. Additionally, viral clearance varied from as early as 94 days to greater than one-and-a-half years after initial infection in those who achieved that status.
"The results significantly expand the available data on the dynamics of hepatitis C viremia preceding seroconversion [conversion from being antibody-negative to positive]," Cox and her associates concluded.The results also stress the significance of reducing the influences that contribute to illicit drug use, as well as ongoing efforts to develop vaccines to prevent chronic HCV infection in that population, Cox's group concluded.
1. Cox AL, Netski DM, Mosbruger T et al. Prospective evaluation of community-acquired acute-phase hepatitis C virus infection. Clin Infect Dis 2005;40:951-8.
2. Challine D, Pellegrin B, Bouvier-Alias M, Rigot P, Laperche L, Pawlotsky JM. HIV and hepatitis C virus RNA in seronegative organ and tissue donors. Lancet 2004 Oct 30;364(9445):1611-2.
3. National Center for Infectious Diseases. Centers for Disease Control and Prevention (CDC). Viral Hepatitis C. Fact Sheet. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/c/fact.htm. Accessed April 6, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
