An Updated Report on Hepatitis C Genotypes
Share
Follow Us
As more detailed information becomes known about any illness, treatment strategies can be increasingly focused on that specific ailment. Treating viral hepatitis exemplifies the advantage of increasing therapeutic specificity. Because higher success rates are associated with how well the hepatitis strain is matched with its prescribed therapy, differentiation between infections is paramount.
Brief History of Viral Hepatitis
Although outbreaks of epidemic jaundice were known in both Greek and Roman times, viral hepatitis was first recognized as a distinct clinical entity in the United States and Europe during the late 18th and early 19th centuries. Originally, viral hepatitis was classified by its route of transmission:
- Through oral and/or fecal route (infectious)
- Through the blood (serum)
During World War II, these two types of viral hepatitis were officially acknowledged; infectious hepatitis was designated as Hepatitis A and serum hepatitis became known as Hepatitis B.
In 1977, the Hepatitis D virus was detected and the development of serological assays for Hepatitis A and Hepatitis B proved that additional hepatitis viruses existed. Hepatitis due to viruses other than the Hepatitis A, Hepatitis B or Hepatitis D viruses were referred to as non-A, non-B hepatitis. In the late 1980s, those infected with non-A, non-B hepatitis were further differentiated with the identification of two more viruses: Hepatitis C and Hepatitis E.
Hepatitis C Classification
Although discovering the root of someone’s liver disease as Hepatitis C is a task in and of itself, there is much more differentiation required to properly address this virus. As of late 2007, the number of known genotypes for Hepatitis C (the genetic make-up of the virus) grew from six to seven distinct viruses. In addition to being classified by genotype, there are over 50 known subtypes of Hepatitis C. As of the end of December 2007, the newly acknowledged genotype 7 has been associated with three separate subtypes.
Hepatitis C genotypes are most common in the following locations:
- Genotypes 1, 2 and 3 = North America and Western Europe
- Genotype 4 = Africa, Egypt and the Middle East, but is increasingly seen in some parts of Europe
- Genotype 5 = Africa and the Middle East
- Genotype 6 = Southeast Asia
- Genotype 7 = Central Africa
In order to prescribe a treatment plan with the highest chances of success, a person must have their particular Hepatitis C genotype and subtype identified. Additionally, knowing the exact strain of Hepatitis C virus is helpful in defining its epidemiology. Once the genotype is identified, it need not be tested again; genotypes do not change during the course of infection.
While the therapeutic responses between Hepatitis C subtypes are not disclosed here, some of the differences among genotypes include:
- Those with genotypes 2 and 3 are almost three times more likely than patients with genotype 1 to respond to therapy with alpha interferon or the combination of alpha interferon and ribavirin.
- A 24-week course of combination treatment is typically adequate for those with genotypes 2 and 3.*
- A 48-week course of combination treatment is typically adequate for those with genotype 1.*
- Data are mixed concerning genotype 4, though its response to combination treatment seems to be somewhere in between the response of genotypes 2 and 3, and genotype 1.
- Recently published research on treating genotype 5 shows that its response to combination treatment is similar to those with genotype 1. However, previous results show that genotype 5 appears to be an easy to treat virus with response rates similar to those of genotypes 2 and 3 after a 48-week course of therapy.
- Preliminary study results show that the response to treatment in those with genotype 6 lies at an intermediate level, between that seen with genotype 1 and genotypes 2 or 3.
- Since it has just recently been discovered as having a distinct genetic make-up, the response to standard combination therapy is not yet established for genotype 7.
*Although some studies claim this duration of time to be ‘typically adequate,’ other trials have demonstrated that longer courses of treatment have lower relapse rates.
Our understanding of the various strains of the Hepatitis C virus is exponentially greater than the knowledge of viral hepatitis just a few decades ago. As more specificity about each type of viral infection is discerned, treatment approaches can be individually tailored. The one-size-fits-all method of prescribing medications is continually shown to be outdated, causing our medical practices to become more advanced. Accompanying this more advanced evolution of infectious hepatology, people fighting Hepatitis C stand their best chance ever of ridding themselves of their particular viral strain.
References:
M. H. Nguyen, E. B. Keefe, Prevalence and treatment of hepatitis C virus: genotypes 4, 5, and 6, Clinical Gastroenterology and Hepatology, October 2005.
www.abbottdiagnostics.com, Hepatitis Learning Guide, Abbott Laboratories, 2006.
www.cdc.gov, Frequently Asked Questions About Hepatitis C, Centers for Disease Control and Prevention, 2007.
www.hivandhepatitis.com, Epidemiology and Treatment Response of Genotype 5 HCV: Researchers Find New Seventh Genotype, Liz Highleyman, hivandhepatitis.com, 2007.
www.stanford.edu, The History of Hepatitis, Tiffany Chang, Stanford University, 1999.
