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| Situation Update No. 22 Ref.no.: EH-20091217-24200-GBR
Situation Update No. 22
On 2010-01-21 at 03:55:02 [UTC]
Event: Epidemic Hazard
Location: United Kingdom Scotland Glasgow
Number of Deads: 7 person(s)
Number of Infected: 14 person(s)
Situation: 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.
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.
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. |  | | | |
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