Hepatitis C virus (HCV) causes chronic inflammation in the liver of humans which can lead to cirrhosis or even liver cancer. The virus is able to get inside cells and make new copies of its genetic material using the machinery of the host cell. The new viral DNA is then packaged into new partials and leaves the cell to infect other cells. Some people have an immune system which is able to clear the virus easily, however, for most of us it develops into a lifelong infection. Although, it is possible to get a liver transplant when it no longer works this is only a short term solution, as the transplanted liver becomes re-infected.
Transmission of HCV requires blood to blood contact. In addition any source of blood or blood products seems to be capable of carrying the virus, even if the source is indirect – like a used razor. Once effective blood screening techniques were developed and used in 1990 post transfusion hepatitis rates decreased from about 8-10% to 5% between 1990-1993. And improved testing methods led drastic reductions in risk (less than 1% after 1993). Needle-stick injuries, contaminated medical equipment, and blood spills in health care settings are also responsible for many cases of HCV. Drug use, however, is the most significant risk for contracting HCV. Sharing contaminated needles increases your chances for developing the infection drastically.
Not everyone experiences symptoms for HCV in the first few months. But some make experience the following symptoms in the first six months (this stage is called acute hepatitis C.):
- a high temperature of 38C (100.4F) or above
- loss of appetite
- stomach pains
For some people the immune systems gets rid of the virus successfully so they experiences no more symptoms but for the remaining cases the virus may persist for years. At this point it is known as chronic hepatitis. Some people still don’t experience any symptoms but for some it can have a significant impact on their lives.
Treating hepatitis C
Majority of HCV cases go untreated as symptoms aren’t visible or not experienced.
Treatment for chronic hepatitis C usually involves using a combination of two medications:
- pegylated interferon (an injection) – a synthetic version of a naturally occurring protein in the body that stimulates the immune system to attack virus cells.
- ribavirin (given as a capsule or tablet) – a type of antiviral drug that stops hepatitis C from spreading inside the body.
The effectiveness of these medications is dependent on the genotype of the HCV. Genotype 1 is more challenging to treat. Only half of people treated with combination therapy will be cured.
Other genotypes respond better to treatment, with a cure rate of around 75–80%.
Genetic Diversity in HCV
Viruses tend to mutate quickly. HCV has a short genome of about 10,000 nucleotides. Unlike human cells Viruses don’t have a proofreading mechanism which can correct mistakes in replications, therefore, when the virus replicates the incorrect nucleotides are retained. Additionally, HCV has a high replication rate. Both these factors mean that a large number of mutations can accumulate over a time. This allows the virus to avoid the immune response if the host, as the changes occur in regions of the genome that eh cells is programmed to recognise.
HCV sample of infected people in different parts of the world can differ by up to 30%. This suggests that there a great amount of genetic diversity in this species. The high rate of mutation makes it difficult to develop a vaccine for the virus as vaccines target specific components of the virus but if this changes the vaccine becomes ineffective.
Hepatitis C is divided into six distinct genotypes with multiple subtypes in each genotype class (classification of a virus based on the genetic material in the RNA strands of the virus. Genotype 1 is the most common type of Hepatitis C genotype in the United States but can also be found in Africa, Europe and japan. However, it is endemic in Africa but epidemic in the Europe and the USA. Genotype 1 is also the hardest to treat with about 50% success rate whereas genotype 2 and 3 have a higher success rate of about 80%.
New drugs for the treatment of hepatitis C are now being investigated in phase II and phase III clinical trials. These include interferon-sparing regimens, which are needed for the treatment of those intolerant to, or medically ineligible for pegylated interferon and ribavirin therapy. New drugs are also targeting viral enzymes to prevent the viral life cycle to complete.