Hepatitis C transmission via injecting drug use: look beyond needles and syringes

Important insights into the continued spread of hepatitis C among injecting drug users are provided by two studies published in the online edition of the Journal of Infectious Diseases.

An international team of investigators showed that infectious quantities of hepatitis C could survive on inanimate surfaces for up to seven days. However, the virus can be rendered inactive by commercially available disinfectants, or heating to a temperature of 65-70°C for approximately 90 seconds.

In a separate study, French investigators detected the virus on 80% of alcohol swabs obtained from injecting drug users. They suggest that the swabs may be shared by users, risking the transmission of hepatitis C.

Holly Hagan of the New York University College of Nursing in an accompanying editorial stated: “The studies contribute new knowledge to our understanding of the mechanisms by which HCV [hepatitis C virus] may be transmitted among PWID [people who inject drugs] via injection-related materials.”

There are an estimated 130 million hepatitis C infections worldwide. Hepatitis C is a blood-borne infection and a major mode of transmission is injecting drug use. Needle and syringe exchange programmes have been introduced in many countries to control the epidemic. The have been highly effective at preventing new HIV infections, but hepatitis C transmissions still continue.

This is possibly because viral load tends to be high in individuals with chronic hepatitis C infection, and even small quantities of contaminated blood are potentially infectious.

A team of investigators led by Juliane Doerrbecker wished to establish a clearer understanding of the survival of the virus, and the effectiveness of disinfectants and heat at rendering the virus non-infectious.

Steel discs were contaminated with infectious quantities of hepatitis C which were then allowed to dry. Reassuringly, commercially available disinfectants were also shown to have “a high virucidal efficacy against HCV.”

Tests also showed that infectious quantities of hepatitis C of approximately 30 TCID₅₀/ml could still be detected on inanimate surfaces up to seven days after contamination. However, the investigators emphasised that “all tested biocides were able to inactivate HCV infectivity to undetectable levels.”

The investigators then examined the effect of heat on the virus. Spoons and/or cookers are used to heat diluted heroin into solutions. The liquid is then drawn into a syringe, potentially contaminating the spoon if hepatitis C-infected blood is present in the syringe. The investigators therefore contaminated spoons with the virus, which were then heated to various temperatures using tea candles.

Infectivity started to decrease at temperatures of approximately 50°C. Levels of the virus fell below the limit of detection when temperatures reached 67-70°C. It generally took between 80 to 95 seconds for heating to produce small bubbles in the spoon.

“Reusing HCV contaminated cookers could lead to infection even if using sterile syringes,” comment the investigators.

Holly Hagan emphasised that injecting drug users rarely heat spoons for more than 15 seconds.

In separate research, Dr Vincent Thibault and his colleagues collected drug-using paraphernalia from individuals known to be infected with hepatitis C. The used paraphernalia included syringes, filters and water cups, swabs for cleaning of skin before injecting and pads employed to stop bleeding after withdrawal of needles. A total of 160 pieces of equipment were collected.

The virus was detected on 44% of the pooled materials. 

A further 620 items used by individuals of unknown infection status were also obtained. Approximately 83% of the pools obtained from swabs had detectable hepatitis C. Moreover, viral load was highest (above 3 log₁₀ iu/ml) within these swab pools.

Hepatitis C was also commonly detected in syringes, but viral load tended to be at low levels (12 to 890 iu/ml).

The investigators therefore believe that there is “a higher chance for PWID to be contaminated though sharing of a tainted spoon rather than a tainted syringe.”

They note that blood was often visible on swabs. The researchers therefore suggest that transmission of the virus could occur if swabs were being used inappropriately. “The chaotic and rushed atmosphere of the injection setting, where swab sharing and mixing could take place, is…an important factor that should be considered.”

Holly Hagan believes the two studies have important implications for hepatitis C prevention programmes. “Cleaning cookers or perhaps impregnating injection equipment with safe biocides may help reduce the incidence of new infections. Promoting safe swab use to emphasize avoidance of reuse seems a prudent measure.”