HIV outbreak among people who inject drugs in Glasgow now involves over 100 infections, many homeless

An HIV outbreak among people who inject drugs in Glasgow involves over 100 cases and is still ongoing, investigators report in The Journal of Infectious Diseases. Genetic sequencing showed that all 104 cases were linked, with two-thirds of diagnoses made after 2014.

Glasgow has excellent harm reduction services for people who inject drugs, including needle exchanges. However, almost all the patients have co-infection with hepatitis C virus (HCV), suggesting sharing of injecting equipment. The outbreak has prompted the development of new services to meet the HIV prevention and care needs of people who inject drugs, many of whom have experience of homelessness.

“Glasgow operates one of the most active injecting equipment provision service in Europe, distributing over 1 million syringes per year,” note the authors. “Nonetheless, the association observed with homelessness suggests that harm reduction services available in Glasgow may have been difficult to access for those in precarious living situations, often with chaotic lifestyles.”


harm reduction

Harm reduction is a set of practical strategies and ideas aimed at reducing negative consequences associated with drug use (including safer use, managed use and abstinence). It is also a movement for social justice built on a belief in, and respect for, the rights of people who use drugs.

transmission cluster

By comparing the genetic sequence of the virus in different individuals, scientists can identify viruses that are closely related. A transmission cluster is a group of people who have similar strains of the virus, which suggests (but does not prove) HIV transmission between those individuals.


In HIV, different strains which can be grouped according to their genes. HIV-1 is classified into three ‘groups,’ M, N, and O. Most HIV-1 is in group M which is further divided into subtypes, A, B, C and D etc. Subtype B is most common in Europe and North America, whilst A, C and D are most important worldwide.

blood-borne virus (BBV)

A virus transmitted through contact with infected blood. Hepatitis B, hepatitis C and HIV are BBVs. (Note that hepatitis B and HIV may also be transmitted through other body fluids).



retention in care

A patient’s regular and ongoing engagement with medical care at a health care facility. 

People who inject drugs are at risk of infection with HIV from sharing injecting equipment and high-risk sexual activity. Since the mid 1980s, the UK has provided harm reduction services to people who inject drugs. These have proved highly effective. From the mid-1990s, HIV diagnoses among people who inject drugs in Glasgow have averaged under ten per year.

However, in 2015 a sharp increase in new HIV diagnoses among people who inject drugs in Glasgow was observed. Routine sequencing showed that many of these infections involved HIV subtype C, which is otherwise rare among people who inject drugs in the UK, suggesting a common source for the outbreak.

A team of investigators therefore analysed the genetic sequence of the virus infecting all people involved in the current outbreak. They especially wanted to see if the cases were related, information which they hoped would assist the development of appropriate prevention and care services.

The researchers identified a tight cluster of 104 cases. All originated in Scotland and involved two HIV mutations: E138A, associated with reduced susceptibility to etravirine and rilpivirine; and V179E which is associated with resistance to nevirapine, efavirenz and etravirine.

A common ancestor to the cluster was identified, a sample obtained from a patient in 2003. The oldest outbreak sequence came from a person who injects drugs diagnosed with HIV in 2005. Five people were diagnosed in 2008 and 2009, a further 27 between 2010 and 2013 and 71 people (68%) after 2014. All were diagnosed in Scotland and reported a history of injecting drug use.

Onward transmissions peaked in 2009, when each HIV infection was associated with an average of two further infections. Analysis suggested that the rate of transmission was currently 1.8 per patient, suggesting the outbreak was still ongoing.

The average transmission interval was estimated at 6.7 months. The investigators were able to divide the outbreak into three distinct clusters, originating in 2010, 2011 and 2012, respectively.

The patients had a mean age of 38 years and 61% were men. Almost all (99%) were White British. There was considerable evidence of social exclusion, with 40% having a history of incarceration and 45% reported ever being homeless. HCV antibodies were present in 98% of people and 71% had chronic HCV infection.

Over a third of people (37%) had viral characteristics suggesting they had been infected with HIV within the previous 12 months.

“The Scottish outbreak is being managed through education of the population at risk and service providers, improved addiction services, increasing provision of needle exchange (eg, greater evening availability), improving accessibility of HIV testing, and outreach services to support early treatment and retention,” conclude the authors. “Further research is needed to demonstrate whether homelessness, or other behavioral factors, played a role in the outbreak.”

A presentation to the recent BHIVA/BASHH conference described the services developed to deal with the outbreak.

These include the appointment of a blood-borne virus specialist nurse to co-ordinate a multidisciplinary team, actively seeking out people by “walking the streets.” Close links have been developed with addiction services to help ensure that patients are linked to HIV care. A scheme has also been introduced to dispense antiretroviral therapy via community pharmacies, especially to people on opioid substitution therapy. In all, 91% of people are currently on antiretroviral therapy and 69% have an undetectable viral load. Services have also been developed to meet the needs of homeless patients, including a weekly consultant-led clinic. 


Ragonnet-Cronin M et al. Recent and rapid transmission of HIV among people who inject drugs in Scotland revealed through phylogenetic analysis. J Infect Dis, online edition. DOI: 10.1093/infdis/jiy130, 2018.

Metcalfe R et al. An outbreak of HIV amongst homeless people who inject drugs (PWIDs) – describing the epidemic and developing an innovative service model. Fourth Joint Conference of the British HIV Association (BHIVA) with the British Association for Sexual Health and HIV (BASHH), Edinburgh, April 2018, abstract 67.