User:Alfred Bertheim/sandbox

Prior to 2011, hepatitis C was treated with up to a full year's administration of the injectable immune stimulant interferon, typically in combination with the ribavirin, a nucleoside analog having a poorly characterized mechanism of action. Significant disadvantages of this regimen include the requirement for 6 months to a full year of treatment, modest efficacy (only about half of patients are cured), and severe side effects. Nearly 100% of patient experience side effects including nausea, vomiting, diarrhea, fever, muscle pain, headache, and a range of psychiatric side effects including insomnia, irritability, and depression. Over 39% of patients require dose modification, most commonly due to anemia or neutropenia. Because of the severity of these side effects and the modest efficacy of the treatment regimen, treatment is usually deferred until it is clearly necessary to prevent fibrosis and declining liver function.

Only about 50% of patients treated with this regimen were cured. (Viral cure is often referred to as a "sustained viral response", meaning that the virus is not detectable in the patient's blood 24 weeks after stopping treatment.) Others either failed to respond to therapy (non-responders), experienced a transient suppression of viral load to undetectable levels that rebounded during or after stopping treatment, or were unable to complete the course of treatment due to the severity of the regimen's side effects. Common adverse effects of interferon therapy include fever, nausea, vomiting, diarrhea, muscle pain, headache, and psychiatric effects including depression, insomnia, and irritability. Over 39% of patients require dose modification, most commonly due to anemia and neutropenia. As a result of these side effects and the relatively slow progress of hepatitis C liver disease in most patients, most patients are not treated until advancing liver disease makes further postponement impossible.

In the New World, most infections are due to genotypes 1a, 1b, and 3. Genotype 1a is responsible for about half of infections in the US, but 1b and 3 predominate in Brazil.  In Europe the distribution varies widely by country, but in most areas genotype 1 and genotype 3 predominate, with 1b being more common than 1a, particularly in Russia and other Eastern European countries. In Japan, approximately 90% of infections are due to genotype 1b. 