Effective direct-acting antiviral or 'DAA' medicines, used without interferon, can now cure most people with hepatitis C. This includes people who previously were considered to be more difficult to treat, including those with HIV co-infection, severe liver disease, prior treatment failure and people who use drugs.

DAAs attack HCV at various steps of its lifecycle. Like HIV treatment, using a combination of drugs that work in different ways is more effective and prevents the development of resistance. But unlike current HIV treatment, hepatitis C treatment can lead to a permanent cure.

The newest DAAs cure more than 90% of people with chronic hepatitis C. Some can be taken as a once-daily combination pill, and some are active against all HCV genotypes (known as 'pangenotypic'). They are well tolerated and treatment usually lasts just three months.

In comparison, the old standard of care – pegylated interferon alfa (Pegasys or PegIntron) plus ribavirin – required weekly injections, had to be taken for six months to a year, caused difficult side-effects including flu-like symptoms and depression, and only cured about half of treated people.

Because interferon-based therapy was so challenging, hepatitis C treatment was traditionally recommended mainly for people showing signs of, or at higher risk for, liver disease progression.

With the new drugs, however, many experts now recommend that everyone with hepatitis C should be treated, regardless of liver disease severity, and say there is little reason to wait. People with advanced fibrosis or cirrhosis need treatment most urgently.

Treatment is more effective when people have not yet developed severe liver disease. Early treatment can avert years of HCV-related symptoms and conditions. Curing hepatitis C halts viral transmission, and studies are starting to show that widespread treatment is reducing new HCV infections. But, due to their high prices, the new drugs are not available to everyone with hepatitis C in the UK and in many other countries. Treatment is prioritised for people with more advanced liver disease but co-infection with HIV may be considered a reason for earlier treatment.

A number of factors can help predict how well hepatitis C treatment is likely to work for you.

Before starting treatment, it is important to have a test to see what genotype of HCV you have. This determines which direct-acting antiviral drugs (DAAs) will work and predicts treatment response. Some DAAs are 'pangenotypic' or active against all genotypes.

There are at least six major HCV genotypes. Genotype 1 is the most common type in the UK, Europe and the US. It has two subtypes, 1a and 1b. Genotype 1 was hard to treat with interferon-based therapy, but it can be successfully treated with all approved DAAs. However, genotype 1a is harder to treat than 1b.

HCV genotype 2 is less common worldwide. It responded best to interferon-based treatment, but is susceptible to fewer DAAs than genotype 1. Genotype 3 is the most common type in the Indian sub-continent and Southeast Asia, but it is also found in the UK. Genotype 3 has been the hardest to treat with DAAs, but newer pangenotypic drugs are highly effective against it.

Genotype 4 is the most common type of HCV in the Middle East and North Africa, but it has also been seen in hepatitis C outbreaks in the UK and Europe. Genotype 4 generally responds to the same DAAs as genotype 1. Genotype 5 and 6 are less common and less well-studied.

Treatment is more effective during the acute stage of HCV infection (the first six months), rather than after you have developed chronic infection. Some experts think it is best to start treatment during this stage because treatment is easier, and curing hepatitis C quickly prevents transmission. But others prefer to wait six months to see if the immune system will naturally clear the virus.

People with chronic infection are more likely to be cured if they are being treated for the first time than if they are being re-treated after prior unsuccessful therapy (known as being ‘treatment experienced’). However, most people can be successfully treated with DAAs regardless of their previous treatment history.

In addition to viral factors, the degree of liver damage and presence of cirrhosis also predict treatment effectiveness. People with cirrhosis have lower response rates, and those with very advanced or decompensated liver disease are more likely to experience complications during treatment. But again, most people with advanced disease can now be successfully treated.

Factors such as age, sex and race or ethnicity played a role in how well interferon-based therapy worked. For example, people of African descent had lower response rates than white people because they had a less favourable form of a gene called IL28B. But these factors have little or no impact on the effectiveness of modern DAAs.