Public health outcome of Tuberculosis Cluster Investigations, England 2010-2013.

OBJECTIVES: Tuberculosis (TB) is a serious re-emergent public health problem in the UK. In response to rising case incidence a National TB Strain-Typing Service based on molecular strain-typing was established. This facilitates early detection and investigation of clusters, targeted public health action, and prevention of further transmission. We review the added public health value of investigating molecular TB strain-typed (ST) clusters. METHODS: A structured questionnaire for each ST cluster investigated in England between 1 January 2010 and 30 June 2013 was completed. Questions related to epidemiological links and public health action and the perceived benefits of ST cluster investigation. RESULTS: There were 278 ST cluster investigations (CIs) involving 1882 TB cases. Cluster size ranged from 2 to 92. CIs identified new epidemiological links in 36% of clusters; in 18% STs were discordant refuting transmission thought to have occurred. Additional public health action was taken following 23% of CI. CONCLUSIONS: We found positive benefits of TB molecular ST and CI, in identifying new epidemiological links between cases and taking public health action and in refuting transmission and saving resources. This needs to be translated to a decrease in transmission to provide evidence of public health value in this low prevalence high resource setting.

A large outbreak of gastrointestinal illness at an open-water swimming event in the River Thames, London.

Open-water swimming is increasingly popular, often in water not considered safe for bathing. Limited evidence exists on the associated health risks. We investigated gastrointestinal illness in 1100 swimmers in a River Thames event in London, UK, to describe the outbreak and identify risk factors. We conducted a retrospective cohort study. Our case definition was swimmers with any: diarrhoea, vomiting, abdominal cramps lasting ⩾48 h, nausea lasting ⩾48 h, with onset within 9 days after the event. We used an online survey to collect information on symptoms, demographics, pre- and post-swim behaviours and open-water experience. We tested associations using robust Poisson regression. We followed up case microbiological results. Survey response was 61%, and attack rate 53% (338 cases). Median incubation period was 34 h and median symptom duration 4 days. Five cases had confirmed microbiological diagnoses (four Giardia, one Cryptosporidium). Wearing a wetsuit [adjusted relative risk (aRR) 6·96, 95% confidence interval (CI) 1·04-46·72] and swallowing water (aRR 1·42, 95% CI 1·03-1·97) were risk factors. Recent river-swimming (aRR 0·78, 95% CI 0·67-0·92) and age >40 years (aRR 0·83, 95% CI 0·70-0·98) were protective. Action to reduce risk of illness in future events is recommended, including clarification of oversight arrangements for future swims to ensure appropriate risk assessment and advice is provided.

Selection of population controls for a Salmonella case-control study in the UK using a market research panel and web-survey provides time and resource savings.

Timely recruitment of population controls in infectious disease outbreak investigations is challenging. We evaluated the timeliness and cost of using a market research panel as a sampling frame for recruiting controls in a case-control study during an outbreak of Salmonella Mikawasima in the UK in 2013. We deployed a web-survey by email to targeted members of a market research panel (panel controls) in parallel to the outbreak control team interviewing randomly selected public health staff by telephone and completing paper-based questionnaires (staff controls). Recruitment and completion of exposure history web-surveys for panel controls (n = 123) took 14 h compared to 15 days for staff controls (n = 82). The average staff-time cost per questionnaire for staff controls was £13·13 compared to an invoiced cost of £3·60 per panel control. Differences in the distribution of some exposures existed between these control groups but case-control studies using each group found that illness was associated with consumption of chicken outside of the home and chicken from local butchers. Recruiting market research panel controls offers time and resource savings. More rapid investigations would enable more prompt implementation of control measures. We recommend that this method of recruiting controls is considered in future investigations and assessed further to better understand strengths and limitations.

Prisoners at ultra-high-risk for psychosis: a cross-sectional study.

BACKGROUND: The definition of ultra-high risk (UHR) for psychosis was derived from community-based help-seeking populations. Prisoners have high rates of psychosis and other severe mental health (MH) problems. They also have high rates of risk factors for psychiatric morbidity and yet they are among the populations who are less likely to seek help in the community. Despite a policy of equivalence of care for individuals in prison there are no early intervention services for psychosis in prisons in the UK. This was a study exploring feasibility of introducing such a service into a local London prison. This paper discusses the differences in MH profile of prisoners who met criteria for at-risk mental state compared with those who did not. METHOD: A two-stage procedure was used. Participants in a local London prison were routinely screened in the first week of arrival in prison with the Prodrome Questionnaire - Brief Version (PQ-B; Loewy et al. 2011). Those that screened positive as well as a small sample of those who screened negative underwent a further semi-structured assessment to see whether they met criteria for UHR state. Data on self-harm and suicide attempt, family psychiatric history, and anxiety and depression was also collected. RESULTS: A total of 891 prisoners were screened, 44% of whom screened positive. A total of 354 underwent second stage assessment, 60 of whom had screened negative. Four groups were identified: those that had no MH problems, a group experiencing First Episode Psychosis, those at UHR of psychosis and a group with other MH problems. The UHR state and Psychotic groups had very similar MH profiles of symptoms and distress. Prisoners with no MH problems were at the other end of the spectrum with few symptoms and little distress. The Other group fell in between this group and the psychotic spectrum group in terms of symptomology and distress. CONCLUSIONS: This study is the first to examine risk for psychosis in an adult male prison population. We identified a broad spectrum of MH disorder for which there is little current service provision in prisons. Screening early in the custodial process has the potential to identify unmet MH need and has implications for keeping individuals safe in custody. A long-term strategic approach is required to address MH need in prisons.

The prospective evaluation of the TB strain typing service in England: a mixed methods study.

BACKGROUND: In response to rising TB notification rates in England, universal strain typing was introduced in 2010. We evaluated the acceptability, effectiveness and cost-effectiveness of the TB strain typing service (TB-STS). METHODS: We conducted a mixed-methods evaluation using routine laboratory, clinic and public health data. We estimated the effect of the TB-STS on detection of false positive Mycobacterium tuberculosis diagnoses (2010-2012); contact tracing yield (number of infections or active disease per pulmonary TB case); and diagnostic delay. We developed a deterministic age-structured compartmental model to explore the effectiveness of the TB-STS, which informed a cost-effectiveness analysis. RESULTS: Semi-structured interviews explored user experience. Strain typing identified 17 additional false positive diagnoses. The TB-STS had no significant effect on contact tracing yield or diagnostic delay. Mathematical modelling suggested increasing the proportion of infections detected would have little value in reducing TB incidence in the white UK-born population. However, in the non-white UK-born and non-UK-born populations, over 20 years, if detection of latent infection increases from 3% to 13% per year, then TB incidence would decrease by 11%; reducing diagnostic delay by one week could lead to 25% reduction in incidence. The current TB-STS was not predicted to be cost-effective over 20 years (£95 628/quality-adjusted life-years). Interviews found people had mixed experiences, but identified broader benefits, of the TB-STS. CONCLUSIONS: To reduce costs, improve efficiency and increase effectiveness, we recommend changes to the TB-STS, including discontinuing routine cluster investigations and focusing on reducing diagnostic delay across the TB programme. This evaluation of a complex intervention informs the future of strain typing in the era of rapidly advancing technologies.

No evidence of transmission from an acute case of hepatitis A in a foodhandler: follow-up of almost 1,000 potentially exposed individuals, London, United Kingdom, April 2012.

Identification of acute hepatitis A virus (HAV) infection in a foodhandler in a London hotel led to a large incident response. We identified three potentially exposed groups: hotel staff who had regularly consumed food prepared by the case and shared toilet facilities with the case, patients who shared the same hospital ward as the case and hotel guests who consumed food prepared by the case. We arranged post-exposure HAV vaccination for all 83 potentially exposed hotel staff and all 17 patients. We emailed 887 guests advising them to seek medical care if symptomatic, but did not advise vaccination as it was too late to be effective for most guests. Through the International Health Regulations national focal points and the European Union Early warning and response system (EWRS), we communicated the details of the incident to public health agencies and potential risk of HAV transmission to international guests. Potentially exposed hotel staff and guests were asked to complete an online or telephone-administered questionnaire 50 days following possible exposure, to identify any secondary cases. Survey response was low, with 155 responses from guests and 33 from hotel staff. We identified no secondary cases of HAV infection through follow-up.

Preparedness for a major incident: creation of an epidemiology protocol for a health protection register in England.

Large incidents and natural disasters are on the increase globally. They can have a major impact lasting many years or decades; and can affect large groups of people including those that are more susceptible to adverse consequences. Following a major incident, it may be considered necessary to establish a register of those people affected by the incident to provide appropriate advice on relevant immediate and longer-term public health interventions that may be required, provide reassurance to the public that their care is paramount, to reassure the worried well to avoid them inappropriately overwhelming local services, and to facilitate epidemiological investigations. Arrangements for the prompt follow-up of populations after large incidents or disasters have been agreed in England and a protocol for establishing a register of individuals potentially affected by a large incident has been developed. It is important for countries to have a protocol for implementing a health register if the circumstances require one to be in place, and are supported by Public Health Authorities. Health registers facilitate the initial descriptive epidemiology of exposure and provide the opportunity of carrying out long term analytical studies on the affected population. Such epidemiological studies provide a greater understanding of the impact that a large incident can have on health, which in turn helps in the planning of health care provision. Registers can also assist more directly in providing access to individuals in need of physical and mental health interventions. The challenge that still remains is to formally pilot the register in the field and refine it based on that experience.

Investigating an outbreak of Clostridium perfringens gastroenteritis in a school using smartphone technology, London, March 2013.

On 22 March 2013, 150 of 1,255 students (13­17 years) and staff at a school in London reported gastrointestinal symptoms; onset peaked 8 to 12 hours after a lunch served in the school on 21 March. We performed a retrospective cohort study of all students and staff. We defined cases as school attenders on 20 and 21 March with onset of gastrointestinal symptoms between 20 and 23 March. We tested food, environmental and stool samples of cases for common pathogens and bacterial toxins. We administered an online questionnaire via email, encouraging the use of smartphones to respond, to measure risk of illness for food items eaten at school on 20 and 21 March. Survey response was 45%. Adjusted risk ratios were generated in a multivariable analysis. Those who ate chicken balti on 21 March were 19.3 times more likely to become ill (95% confidence interval: 7.3­50.9). Clostridium perfringens was detected in all 19 stool samples collected. Within eight school hours of its launch, 412 of 561 (73%) responders had completed the survey. Hygienic standards in the kitchen were satisfactory. The investigation was done rapidly due to smartphone technology and we recommend considering this technology in future outbreaks.

Epidemiology of tuberculosis in children in London, 2009-2011: are opportunities for prevention being missed?

SETTING: London, United Kingdom. OBJECTIVE: To explore missed opportunities (MO) for the prevention of tuberculosis (TB) in children aged 0-15 years. DESIGN: Parents/guardians of children aged <15 years diagnosed with TB and reported through surveillance were interviewed about bacille Calmette-Guérin vaccination (MO-V) or contact tracing and screening for TB (MO-C) via an algorithm reflecting eligibility. RESULTS: Annual TB incidence was 12 per 100,000 (65/100,000 in Black Africans, 20/100,000 in Indian or Pakistani children). The response rate was 36% (145/405). About 20% of UK-born children had not been vaccinated. MO-V was not associated with any particular factor. Contact with a known TB case before illness had occurred in 71 children (49%; 71% in those aged 0-1 years vs. 30% in those aged 11-15 years), of whom 64 (91%) were diagnosed through contact tracing. MO-C had been conducted in six (4% overall). Children with MO-C were all of Black ethnic origin. Their index cases were family members (within their household) or relatives or family friends from abroad (outside their household). MO-C was not associated with any other factor. CONCLUSION: Although overall few missed opportunities for prevention had occurred, we recommend increased rigour when performing contact tracing in any case where a child may have been exposed.

Outbreak investigation and case-control study: penta-resistant Salmonella Typhimurium DT104 associated with biltong in London in 2008.

In August 2008 an outbreak of Salmonella Typhimurium DT104 occurred in South West London. Sixteen cases were identified with a particular multilocus variable number tandem repeat analysis (MLVA) pattern. In a matched case-control study 14 primary cases were included. These were defined as individuals with gastrointestinal symptoms and Salmonella Typhimurium DT104 isolated from a stool specimen, with a characteristic antibiotic resistance profile and MLVA pattern, and diagnosed in a local laboratory. Four controls per case were matched on age, gender and area of residence. Cases were 26 times more likely than controls to have eaten beef biltong, a South African speciality meat product (odds ratio 25·83, 95% confidence interval 4·92­135·59, P < 0·01). Although environmental investigation failed to identify Salmonella in the food product we conclude that beef biltong consumption led to this outbreak. This conclusion has importance in informing the ongoing risk assessment relating to uncontrolled foodstuffs.

Salmonella enterica serovar Enteritidis phage type 4 outbreak associated with eggs in a large prison, London 2009: an investigation using cohort and case/non-case study methodology.

In September 2009, an outbreak of Salmonella enterica serovar Enteritidis affected 327 of 1419 inmates at a London prison. We applied a cohort design using aggregated data from the kitchen about portions of food distributed, aligned this with individual food histories from 124 cases (18 confirmed, 106 probable) and deduced the exposures of those remaining well. Results showed that prisoners eating egg cress rolls were 26 times more likely to be ill [risk ratio 25.7, 95% confidence interval (CI) 15.5-42.8, P<0.001]. In a case/non-case multivariable analysis the adjusted odds ratio for egg cress rolls was 41.1 (95% CI 10.3-249.7, P<0.001). The epidemiological investigation was strengthened by environmental and microbiological investigations. This paper outlines an approach to investigations in large complex settings where aggregate data for exposures may be available, and led to the development of guidelines for the management of future gastrointestinal outbreaks in prison settings.

The case-cohort design in outbreak investigations.

The use of the case-cohort design for outbreak investigations has been limited. Here we discuss its strengths and limitations based on real and fictitious examples. The case-cohort is a case­control study where controls are sampled from the initial population at risk, and may thus include both cases and non-cases. An advantage of the design, compared to traditional case-control studies, is that risk ratios can easily be obtained directly from the cross-product of exposed and unexposed cases and controls (rare disease assumption is not required). We illustrate this in the context of point source gastrointestinal outbreaks and in field studies on vaccine effectiveness. The design is also useful to investigate multiple outcomes with a unique sample of controls or to test hypotheses when different case-definitions (from the most sensitive to the most specific) are used for a particular outcome. Strengths and limitations are presented, and discussed in the context of outbreak investigations.

Epidemiology of internal contamination with polonium-210 in the London incident, 2006.

BACKGROUND: More than 700 UK residents were tested for possible contamination with polonium-210 ((210)Po) following the alleged poisoning of Mr Alexander Litvinenko in London in November 2006. This paper describes the epidemiology of internal contamination with the radionuclide in this group. METHODS: 11 locations in London had been identified as sufficiently environmentally contaminated with (210)Po to present a health risk to people associated with them. Public health consultant teams identified individuals at risk and offered 24-h urine testing for (210)Po excretion. Prevalence of internal contamination was estimated, and a retrospective cohort analysis was completed for each location. RESULTS: Overall 139 individuals (prevalence 0.19 (95% CI 0.13 to 0.27)) showed evidence of internal contamination with (210)Po, although none with uptakes likely to cause adverse health effects. Substantial prevalence was seen among specific hotel service staff, customers, staff and other users of a hotel bar, office and hospital staff, staff of one restaurant and residents of and visitors to the family home. Increased risks of contamination were seen for a hotel bar in association with occupational, behavioural and temporal factors. Occupational and guest exposure to contaminated areas of hotels were also associated with increased contamination risk. Nurses were more likely to become contaminated than other staff involved in direct patient care. CONCLUSIONS: Uptake of trace amounts of radionuclide in this incident was frequent. Occupational, behavioural and temporal gradients in contamination risk were mostly consistent with a priori site risk assessments. Utility of the investigation methods and findings for future accidental or deliberate environmental contamination incidents are discussed.

Large outbreak of isoniazid-monoresistant tuberculosis in London, 1995 to 2006: case-control study and recommendations.

We conducted a case­control study to examine risk factors for isoniazid-monoresistant Mycobacterium tuberculosis in an ongoing outbreak in London. Cases were defined as individuals with an isoniazid-monoresistant strain diagnosed from 1995 to the third quarter of 2006 with an indistinguishable restriction fragment length polymorphism (RFLP) or mycobacterial interspersed repetitive unit (MIRU)-variable number tandem repeats (VNTR) pattern who were resident in or had epidemiological links with London. Controls were all other individuals reported with tuberculosis to the Health Protection Agency London regional epidemiology unit or the HPA London TB Register during 2000 to 2005. Of 293 cases, 153 (52%) were sputum smear-positive compared with 3,266 (18%) of controls. Cases were more likely to be young adults (aged between 15 and 34 years), born in the United Kingdom (OR: 2.4; 95% CI: 1.7­3.4) and of white (OR: 2.9; 95% CI: 1.8­4.8) or black Caribbean (OR: 12.5; 95% CI: 7.7­20.4) ethnicity, a prisoner at the time of diagnosis (OR: 20.2; 95% CI: 6.7­60.6), unemployed (OR: 4.1; 95% CI: 3.0­5.6), or a drug dealer or sex worker (OR: 187.1; 95% CI: 28.4­1,232.3). A total of 113 (39%) of cases used drugs and 54 (18%) were homeless. Completion of treatment gradually improved in cases from 55% among those diagnosed up to the end of 2002 compared with 65% by the end of 2006. Treatment completion increased from 79% to 83% in controls from 2000 to 2005. There are complex social challenges facing many cases in this outbreak that need to be addressed if medical interventions are to be successful.

Early spread of the 2009 influenza A(H1N1) pandemic in the United Kingdom--use of local syndromic data, May-August 2009.

Following the confirmation of the first two cases of pandemic influenza on 27 April 2009 in the United Kingdom (UK), syndromic surveillance data from the Health Protection Agency (HPA)/QSurveillance and HPA/NHS Direct systems were used to monitor the possible spread of pandemic influenza at local level during the first phase of the outbreak. During the early weeks, syndromic indicators sensitive to influenza activity monitored through the two schemes remained low and the majority of cases were travel-related. The first evidence of community spread was seen in the West Midlands region following a school-based outbreak in central Birmingham. During the first phase several Primary Care Trusts had periods of exceptional influenza activity two to three weeks ahead of the rest of the region. Community transmission in London began slightly later than in the West Midlands but the rates of influenza-like illness recorded by general practitioners (GPs) were ultimately higher. Influenza activity in the West Midlands and London regions peaked a week before the remainder of the UK. Data from the HPA/NHS Direct and HPA/QSurveillance systems were mapped at local level and used alongside laboratory data and local intelligence to assist in the identification of hotspots, to direct limited public health resources and to monitor the progression of the outbreak. This work has demonstrated the utility of local syndromic surveillance data in the detection of increased transmission and in the epidemiological investigation of the pandemic and has prompted future spatio-temporal work.

Recent trends in tuberculosis in children in London.

BACKGROUND: Childhood tuberculosis (TB) represents a sentinel event of recent transmission and is an indication of the effectiveness of prevention and control interventions. We analysed the trends in the epidemiology of TB in children in London aged 0-14 years between 1999 and 2006. METHODS: Data were extracted from the Enhanced TB Surveillance System. RESULTS: Between 1999 and 2006, there were 1370 cases of TB in children. Incidence was higher in older children and in girls. The incidence rates in London Boroughs varied from 0.4/100,000 to 32.7/100,000. Between 1999 and 2006, Black-Africans comprised 49.2% of all TB cases in children, children from the Indian Subcontinent 21.8% and Whites 8.5%. The proportion of cases born in the UK averaged 52.4% during this period. Of non-UK-born children 79.3% were diagnosed with TB within 5 years of entry. CONCLUSIONS: Ethnicity, country of birth and age are important risk factors for development of. With an overall TB incidence in London exceeding 40/100,000, universal BCG immunization of all neonates should be considered across all London boroughs.

Predictors of failure to complete tuberculosis treatment in London, 2003-2006.

SETTING: London, 2003-2006. OBJECTIVES: To investigate tuberculosis (TB) treatment completion failure in London and associated risk factors during 2003-2006. DESIGN: Cross-sectional analysis of treatment outcome and other explanatory variables in a cohort of TB patients reported to the London TB Register from 2003 to 2006. METHODS: An innovative definition of TB treatment outcome more suitable for low-incidence industrialised countries, such as the United Kingdom, was adopted. A multivariable logistic approach was used to assess predictors of unsuccessful outcome. RESULTS: A total of 12,929 TB cases were notified from 2003 to 2006, of which 12% (n = 1536) failed to complete TB treatment. The proportion of cases failing to complete treatment showed a significant decrease from 2003 to 2006 (13% in 2003 vs. 10% in 2006). Males, the elderly, hospitalised patients, short- and long-term immigrants, Whites and the least deprived were more likely to fail to complete treatment. CONCLUSIONS: The proportion of TB treatment success in London exceeded the World Health Organization recommended threshold of 85%. Some specific categories of patients that are more likely to fail to complete treatment should be targeted by health services to enhance their engagement and adherence to the treatment regimen.

Pandemic (H1N1) 2009 influenza in the UK: clinical and epidemiological findings from the first few hundred (FF100) cases.

The UK was one of few European countries to document a substantial wave of pandemic (H1N1) 2009 influenza in summer 2009. The First Few Hundred (FF100) project ran from April-June 2009 gathering information on early laboratory-confirmed cases across the UK. In total, 392 confirmed cases were followed up. Children were predominantly affected (median age 15 years, IQR 10-27). Symptoms were mild and similar to seasonal influenza, with the exception of diarrhoea, which was reported by 27%. Eleven per cent of all cases had an underlying medical condition, similar to the general population. The majority (92%) were treated with antiviral drugs with 12% reporting adverse effects, mainly nausea and other gastrointestinal complaints. Duration of illness was significantly shorter when antivirals were given within 48 h of onset (median 5 vs. 9 days, P=0.01). No patients died, although 14 were hospitalized, of whom three required mechanical ventilation. The FF100 identified key clinical and epidemiological characteristics of infection with this novel virus in near real-time.

The international follow-up of individuals potentially exposed to polonium-210 in London 2006.

OBJECTIVES: Following a death from polonium-210 ((210)Po), contamination was found at several sites in London. This paper describes the UK Health Protection Agency's follow-up and assessment of individuals resident overseas who were potentially exposed to (210)Po. STUDY DESIGN: Descriptive follow-up study. METHODS: Individuals were classified into three exposure groups (higher, lower and unknown). Presence and degree of internal contamination were measured by 24-h urinary (210)Po activity (mBq/day). Results over 30mBq/day were taken to indicate probable contact with (210)Po in this incident. Dose assessments were conducted to determine degree of exposure and to identify individuals requiring further follow-up. RESULTS: Overall, 664 potentially exposed persons from 52 countries and territories were identified. Of these, 157 (24%) were in the higher exposure category, and urinary measurements were reported for 31% (48/157). Results for 19% (9/48) of those at higher exposure were more than 30mBq/day. For those at lower exposure, the percentage was 4% (3/68). Results above 30mBq/day were significantly more likely to be reported for the higher exposure category than the lower exposure category (Fisher's exact test P=0.010). Reported dose assessments suggested that identified individuals were not at increased health risk in the long term. Challenges and practical lessons were identified during the investigation. CONCLUSION: The results suggest that it is unlikely that any overseas resident had significant internal contamination with (210)Po. However, this incident clearly demonstrated the scale of international involvement likely to be necessary in other public health emergencies in large cities. The lessons identified have implications for the international health community, particularly with regard to the follow-up of individuals exposed to radiation in one country who then travel to another.

Assessing public health risk in the London polonium-210 incident, 2006.

OBJECTIVES: Mr Alexander Litvinenko died in a London hospital on 23 November 2006, allegedly from poisoning with the radionuclide polonium-210 ((210)Po). Associated circumstances required an integrated response to investigate the potential risk of internal contamination for individuals exposed to contaminated environments. STUDY DESIGN: Descriptive study. METHODS: Contaminated locations presenting a potential risk to health were identified through environmental assessment by radiation protection specialists. Individuals connected with these locations were identified and assessed for internal contamination with (210)Po. RESULTS: In total, 1029 UK residents were identified, associated with the 11 most contaminated locations. Of these, 974 were personally interviewed and 787 were offered urine tests for (210)Po excretion. Overall, 139 individuals (18%) showed evidence of probable internal contamination with (210)Po arising from the incident, but only 53 (7%) had assessed radiation doses of 1mSv or more. The highest assessed radiation dose was approximately 100mSv. CONCLUSIONS: Although internal contamination with (210)Po was relatively frequent and was most extensive among individuals associated with locations judged a priori to pose the greatest risk, a high degree of assurance could be given to UK and international communities that the level of health risk from exposure to the radionuclide in this incident was low.