An investigation is currently underway to explore and control an outbreak of Bacillus anthracis among drug users (mainly injecting) in Scotland. Contaminated heroin or a contaminated cutting agent mixed with the heroin is considered to be the most likely source and vehicle of infection. Heroin users have been advised of the risk. The risk to the general public is regarded as very low.
On 10 December 2009 the National Health Service Greater Glasgow and Clyde (NHS GGC) was informed of two hospitalised injecting drug users (IDUs) with blood cultures positive for Bacillus sp. Further testing identified that these cultures were provisionally positive for anthrax on 16 December 2009. One of the patients had died earlier that day. The other patient was stable and responding to a cocktail of antibiotics.
In the following weeks further suspected cases were reported and investigated in Glasgow, Lanarkshire, Tayside, Forth Valley, Fife and other Scottish NHS Board areas. As of 14 January 2010, there were a total of 14 confirmed cases of anthrax infection in Scotland of whom seven have died: seven confirmed cases in the NHS GGC area, four fatal; three cases in Lanarkshire NHS area, one of whom remains in hospital; two fatal cases in Tayside one fatal case in the Forth Valley NHS area, and one surviving case in Fife. All cases reported a history of taking heroin by intramuscular, intravenous or subcutaneous injection and/or by other routes including smoking or snorting.
Case definitions were established to classify cases as ‘confirmed’, ’probable’ or ‘possible’ . Only laboratory-confirmed cases are being reported publicly. The 14 confirmed cases are 10 men and four women* aged between 27 and 55 years for the men and between 39 and 43 years for the women. The mean age of the cases is 38 years for both men and women. The mean age of the fatal cases is slightly higher at 42 years.
The first confirmed case in Glasgow was admitted to hospital on 7 December 2009; the latest confimed case was admitted to hospital in Dundee on 6 January 2010 and died on 8 January following a rapid deterioration. Over the five weeks of the outbreak to date, the peak incidence of admissions was in week 3 (six new confirmed cases, week beginning 28 December 2009), dropping to one new confirmed case in week 4 (beginning 4 January 2010). The peak of the outbreak may therefore have already occurred, but it is too early yet to state this with confidence.
There are estimated to be around 55,000 (illegal) drug users in Scotland (not all of whom use heroin) giving a very approximate incidence of 2.5 cases per 10,000 drug users. This is set in the context of approximately 34% of IDUs reporting an injection site wound in any year.
Generally, the cases have presented with inflammation or abscesses related to sites of heroin injection. Symptoms began between one and two days or longer after injection of heroin and admission to hospital generally followed within four days. Localised lesions developed into necrotising fasciitis in a number of cases, some of whom died. The fatal cases in Glasgow (three men and one woman) died between three and seven days after admission. Cellulitis with very marked oedema has been noted in limbs with infection sites in a number of these cases. In a few cases the presentation has been of patients in advance stages of systemic sepsis some of whom died within hours. At least two cases presented with symptoms thought of at initial assessment as suggestive of a sub-arachnoid haemorrhage or haemorrhagic meningitis. Others presented with relatively localised lesions which have not progressed. The range of presentations is therefore wide and inconsistent.
Diagnosis has been confirmed by isolation of Bacillus anthracis in early blood cultures in some patients, supported by PCR testing of blood or excised tissues at the Health Protection Agency (HPA) Special Pathogens Reference Unit (SPRU) at Porton Down. In others, no blood cultures were obtained before antibiotic therapy was started and no organism was cultured, but PCR evidence was obtained. In at least one case confirmation was on the basis of finding only significant anti-toxin antibodies on sera following treatment with antibiotics. This raises the possibility that other milder cases may have not been identified who may have antibody evidence of exposure to the organism. Where practical (in the context of the case population), possible cases who have not been confirmed by isolation or PCR will be followed up to obtain convalescent sera, to identify late sero-converters.
Management has consisted of treatment with relevant intravenous antibiotics, with the close involvement of local microbiologists, and surgical debridement where appropriate.
Four cases have been treated with anthrax immunoglobulin (AIG) supplied courtesy of the United States Centres for Disease Control and Prevention (US CDC), under the supervision of CDC staff who were temporarily on site to assist the investigation and have provided advice and guidance in relation to recent US experience with clinical anthrax infection. AIG was provided under the CDC investigational new drug protocol.
Information on injecting drug use, social circumstances and other possible risk factors for developing anthrax has been obtained from these cases wherever possible. A difficulty in this investigation is obtaining reliable accurate histories of recent drug use, given the nature of the situation and the seriousness of illness in some cases. Some cases died before complete histories could be obtained. Information collected to date has indicated that the majority (but not all) had a recent history of injecting heroin, which they had obtained primarily within the Greater Glasgow and Clyde area or neighbouring Lanarkshire. For more recent cases residing outside the Glasgow/Lanarkshire area, the source of their heroin is under investigation. There does not appear to be another common factor for possible anthrax exposure other than the acquisition and taking of heroin by one or more methods. Dissolving agents (mainly citric acid) were purchased at separate locations and are not considered to be implicated as possible vehicles of transmission or contamination.
Response to the outbreak
Initially the outbreak was managed via an Outbreak Control Team (OCT) based in NHS GGC with support from local microbiologists, Strathclyde Police, Health Protection Scotland, and the HPA SPRU (who have acted as the reference laboratory for the confirmation of all cases to date).
The OCT formulated three working hypotheses. Firstly, that there was anthrax in the heroin which may have entered the supply chain at any point from its original source to the final point of acquisition. Secondly, that either the dissolving agent or cutting agent were contaminated with anthrax. Thirdly, that there was an as yet undiscovered link between the cases.
Information was released via the press advising the drug injecting community of the additional risk associated with taking heroin and that they should seek urgent medical advice if they developed an infection. Subsequently specific information leaflets and posters have been developed in collaboration with the Scottish Drugs Forum.
Evidence suggests that subcutaneous and intramuscular routes have been associated with the majority of infections and confirmed cases to date. However, some cases reported multiple routes of administration in sequence. Hence, in contrast to the previous outbreak of Clostridium novyi infection (which also affected IDUs in Scotland in 2000) [2,3], it has not been possible to offer advice on harm-minimising methods of taking heroin. Due to the potential risk of inhalational anthrax from smoking (or snorting) heroin, and the potential risk from injecting anthrax spores intravenously, from ingesting or from any other parenteral route of administration, addiction services and pharmacies were alerted to the fact that no ’safe’ route of administration of heroin could be advocated. The key harm reduction advice message remains that focused on avoiding the use of heroin if possible and seeking alternatives via drug treatment services, highlighting awareness of the dangers and early symptom identification. General practitioners, hospital departments, and microbiology departments were also alerted. Information has been cascaded across all NHS Boards in Scotland and to specialist community addiction services.
Progress of investigation
Given the confirmation of cases outside the Glasgow conurbation, the outbreak investigation has now been upgraded to a national OCT, coordinated by Health Protection Scotland. Representatives of agencies working with drug users have also been co-opted to the national OCT including the Scottish Drugs Forum and Scottish Drug Deaths Forum. The most likely cause of the outbreak is considered to be exposure by injection (or other routes) to heroin either directly contaminated at the source or contaminated as a result of mixing with other substances contaminated with anthrax at some point in the supply chain. The distribution of cases suggests either that small batches of contaminated heroin may still be circulating in Scotland or that there is a continuing source of contamination in material used to cut (dilute down) the heroin before supply to end users. Further investigations are proceeding to try to trace the supply network and validate the existing hypothesis.
Risk assessments have been undertaken regarding the potential risks to others including health service staff. Police and others involved in searching premises and in handling the cases’ belongings. To date there has been no evidence to suggest a risk to the general public or any other parties who have had access to clothing, belongings or the living quarters of cases. No special protective measures are therefore being advised at present and there are no plans to decontaminate any such personal items or premises, on the basis that the risk to date has been confined to an association with personal intake of heroin, not other casual exposures.
Although rare, outbreaks or cases of illness among IDUs have been documented in recent years. In 2000, an outbreak among IDUs, involving 60 cases and 20 deaths, occurred in Scotland. The most frequently isolated pathogen among the cases was C. novyi and transmission was believed to have occurred via a contaminated batch of heroin [2,3]. Similarly in 2000, a case of ’injectional’ anthrax was identified in a heroin-injecting drug user in Norway. A contaminated batch of heroin was believed to be the source of the infection .
Between December 2003 and April 2004, reports of C. hystoliticum from 12 cases of infection in IDUs were identified in England and Scotland. Again, it was believed that the source of the infection was a contaminated batch of heroin distributed across the UK .
Setting an appropriate diagnostic threshold for this outbreak is a challenge in that approximately 34% of IDUs per year report signs of an infected injection site. Hence wound infections in this population are not unusual. However, none of the cases have presented with a classical cutaneous anthrax pattern. It is perhaps surprising given the source and nature of heroin preparation and anecdotal reports that heroin is transported in animal skins, that more cases of infections in heroin users has not been identified before now.
The role of CDC in providing advice and support by way of personnel and a supply of the anthrax immunoglobulin (AIG) is gratefully acknowledged, in particular Dr. Nicki Pesik and Dr. Theresa Smith regarding use of the AIG and colleagues Dr. Sean Shadomy and Dr. Kendra Stauffer in support.
* Authors correction: In the original version the sentence read 11 men and three women. This was corrected on request of the authors on 15 January 2010.
- Health Protection Scotland. Anthrax in Drug Users: Case Definitions Version 5.0. 13 January 2010. Available from: http://www.hps.scot.nhs.uk/anthrax/documents/case-definition-anthrax-outbreak-v5.pdf
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