Each injecting drug user carrying hepatitis C is likely to pass the virus on to 20 other people, a study has found.
Helping these people and stopping the spread of hepatitis C is our ultimate target
Half the transmissions would occur during the first two years after the original carrier is infected.
Researchers are calling for early diagnosis and treatment of injecting drug users to prevent hepatitis C contagion by so-called ‘super-spreaders’.
Hepatitis C causes severe liver damage but often produces no symptoms for many years. Many of those carrying the virus are not aware they are infected.
The virus is highly infectious and easily spread by dirty needles. Up to nine out of 10 cases of hepatitis C in the UK are believed to be the result of injecting illegal drugs.
An estimated 255,000 people in England have hepatitis C, but the true figure may be far higher.
Globally, up to 180 million people live with the virus, which has been labelled as a major problem by the World Health Organisation.
A fifth of those infected will develop cancer or cirrhosis of the liver after carrying the virus for 20 years. No vaccine is currently available for hepatitis C, as it is for other forms of hepatitis. The new study used a combination of epidemiological surveillance and molecular information to describe in detail how the virus spreads through a population.
Researchers drew on data from four hepatitis C epidemics in Greece, studying frozen DNA samples and data from drug trials involving almost 1,000 patients. A mathematical model was used to estimate secondary infection rates and how long it took for such transmission to occur.
The findings are published in the online journal Public Library of Science Computational Biology.
Lead scientist Gkikas Magiorkinis, from Oxford University, said: “For the first time we show that super-spreading in hepatitis C is led by intravenous drug users early in their infection.
“Using this information we can hopefully soon make a solid argument to support the scaling-up of early diagnosis and antiviral treatment in drug users. Helping these people and stopping the spread of hepatitis C is our ultimate target.”