Pharmacy screening for hepatitis C could identify thousands more people with the virus, experts said today.
Up to half a million people are thought to be living with the disease in the UK but do not know it.
Now, a pilot scheme in 19 pharmacies across the UK has identified a far higher rate of people with the virus than the number picked up by family doctors.
One in six people tested in pharmacies came back as positive for hepatitis C, which can be transmitted through infected blood, or hepatitis B, which can also be transmitted through other bodily fluids.
The Royal Pharmaceutical Society and the Hepatitis C Trust said the results show the need for wider screening.
Hepatitis C can cause serious liver disease and liver cancer but many people carry the disease for years with no symptoms.
Famous sufferers include Body Shop founder Dame Anita Roddick, who caught the virus from a blood transfusion she received during the birth of her daughter. She died in 2007.
Celebrities with the virus include actress Pamela Anderson, guitarist Keith Richards and singers Marianne Faithfull and Natalie Cole.
Anyone given a blood transfusion before September 1991 or blood products before 1986 could be at risk of infection, and a major route of transmission is people sharing needles for injecting drugs.
Less common ways of passing on the virus include from mother to child before or during birth, unprotected sex with someone who has the virus and having medical and dental treatment abroad.
People having tattoos, ear or body piercing, acupuncture, electrolysis and semi-permanent make-up are also at risk if unsterile equipment is used.
Sharing razors or toothbrushes which may have been contaminated with blood also carries a risk.
Today's results involved pharmacies offering the test to patients at risk, who were all identified through a series of questions designed to determine their chance of exposure.
From 234 tests carried out, 35 people were diagnosed with hepatitis C (15% of tests) and four people with hepatitis B (2% of tests).
In GP surgeries, 4% of targeted tests find positive hepatitis C patients and 2% of find hepatitis B patients.
Charles Gore, chief executive of the Hepatitis C Trust said: "It is a tragedy that increasing numbers of people with hepatitis B and C are dying - often from particularly unpleasant liver cancer which these viruses can cause.
"It is a tragedy because they have generally been living with the virus for years and could have been given treatment at any point, if only they had been diagnosed.
"We desperately need new approaches to testing that will find the undiagnosed patients and this pilot study shows pharmacy testing could be just what is needed."
The Health Protection Agency estimates there are around 250,000 hepatitis C positive people in the UK although some experts have put this figure at nearer half a million.
Around 70,000 people in England and Wales have been diagnosed.
Gary Warner, a pharmacist on the Isle of Wight, said: "The results speak for themselves - pharmacies see a different cohort of people to those who see their GP and therefore we can access and diagnose people who otherwise would not have been tested."
A spokesman for the Department of Health said: "We welcome that pharmacies and local NHS organisations are working together to increase detection and diagnosis of hepatitis C in those at risk of infection in an accessible and innovative way.
"The Department of Health is providing grant funding to the Hepatitis C Trust to work collaboratively with local NHS organisations and community pharmacies to provide pharmacy-based hepatitis C testing, following a successful pilot."Reuse content