Drug use in the UK is among the highest reported in Western Europe. In 2017- 2018, around 3.0 million (9.0%) 16-59 year olds in England and Wales reported using a drug in the last year. This proportion has reduced over the past 2 decades, but has remained stable over the last 8 years. The Scottish Crime and Justice Survey (2014- 15) estimated 6.0% of 16-59 year olds reported using a drug in the past 12 months. There were 199,339 people who received treatment for drug misuse in England in 2016-17. Of those who newly presented to treatment, 37% were currently injecting, or had previously injected, drugs. The proportion currently or previously injecting among new presentations to drug treatment differed between those starting treatment for opiates (60%) and non-opiates (9%)

People who inject drugs (PWID) are vulnerable to a wide range of viral and bacterial infections, which can result in high levels of morbidity and mortality. HIV, hepatitis B virus and hepatitis C virus are very effectively transmitted through the use of shared needles and syringes. Unsterile injection practices are also associated with bacterial infections such as Staphylococcus aureus and Group A streptococci. Rare but lifethreatening infections with spore-forming bacteria such as tetanus, botulism and anthrax can be associated with contaminated drugs. Public health surveillance of infectious diseases, and the associated risk and protective behaviours among PWID, provides important information to understand the extent of these infections, the risk factors for their acquisition and for monitoring the effectiveness of prevention measures.