Salmonella Saintpaul outbreak associated with cantaloupe consumption, the United Kingdom and Portugal, September to November 2023.

In September 2023, the UK Health Security Agency identified cases of Salmonella Saintpaul distributed across England, Scotland, and Wales, all with very low genetic diversity. Additional cases were identified in Portugal following an alert raised by the United Kingdom. Ninety-eight cases with a similar genetic sequence were identified, 93 in the United Kingdom and 5 in Portugal, of which 46% were aged under 10 years. Cases formed a phylogenetic cluster with a maximum distance of six single nucleotide polymorphisms (SNPs) and average of less than one SNP between isolates. An outbreak investigation was undertaken, including a case-control study. Among the 25 UK cases included in this study, 13 reported blood in stool and 5 were hospitalized. One hundred controls were recruited via a market research panel using frequency matching for age. Multivariable logistic regression analysis of food exposures in cases and controls identified a strong association with cantaloupe consumption (adjusted odds ratio: 14.22; 95% confidence interval: 2.83-71.43; p-value: 0.001). This outbreak, together with other recent national and international incidents, points to an increase in identifications of large outbreaks of Salmonella linked to melon consumption. We recommend detailed questioning and triangulation of information sources to delineate consumption of specific fruit varieties during Salmonella outbreaks.

Shedding and exclusion from childcare in children with Shiga toxin-producing Escherichia coli, 2018-2022.

Excluding children with Shiga toxin-producing Escherichia coli (STEC) from childcare until microbiologically clear of the pathogen, disrupts families, education, and earnings. Since PCR introduction, non-O157 STEC serotype detections in England have increased. We examined shedding duration by serotype and transmission risk, to guide exclusion advice. We investigated STEC cases aged <6 years, residing in England and attending childcare, with diarrhoea onset or sample date from 31 March 2018 to 30 March 2022. Duration of shedding was the interval between date of onset or date first positive specimen and earliest available negative specimen date. Transmission risk was estimated from proportions with secondary cases in settings attended by infectious cases. There were 367 cases (STEC O157 n = 243, 66.2%; STEC non-O157 n = 124, 33.8%). Median shedding duration was 32 days (IQR 20-44) with no significant difference between O157 and non-O157; 2% (n = 6) of cases shed for ≥100 days. Duration of shedding was reduced by 17% (95% CI 4-29) among cases reporting bloody diarrhoea. Sixteen settings underwent screening; four had secondary cases (close contacts' secondary transmission rate = 13%). Shedding duration estimates were consistent with previous studies (median 31 days, IQR 17-41). Findings do not warrant guidance changes regarding exclusion and supervised return of prolonged shedders, despite serotype changes.

Multinational collaboration in solving a European Salmonella Braenderup outbreak linked to imported melons, 2021.

A genomic cluster of Salmonella Braenderup ST22, a serovar of Salmonella enterica subsp. enterica which causes symptoms of gastrointestinal illness, was notified by Danish authorities to the European Centre for Disease Prevention and Control (ECDC) on 3 May 2021. By 6 July 2021, S. Braenderup outbreak cases (n = 348) had been reported from 12 countries in the European Union/European Economic Area (EU/EEA) and the United Kingdom (UK), including 68 hospitalised cases. With support from affected EU/EEA countries, and in partnership with the European Food Safety Authority (EFSA), ECDC established an international outbreak investigation team to rapidly identify the source and prevent outbreak spread. Consumption information was shared with affected countries through a standard line list, revealing that 124 of 197 cases (63%) reported having eaten (any) melons within 7 days prior to disease onset. The speed and completeness of the investigation, which identified the outbreak vehicle as galia melons imported from Honduras in June 2021, was a direct result of extensive collaboration and information sharing between countries' national food safety and public health authorities. This article describes the outbreak and the benefits, successes, and challenges of multi-country collaboration for consideration in future large foodborne outbreaks across Europe.

A decade of Campylobacter and Campylobacter bacteraemias in a district general hospital and the surrounding London and South East region, England.

BACKGROUND: Campylobacter bacteraemia is a rare complication of the most common bacterial gastrointestinal infection but is associated with significant morbidity and mortality. There is limited data describing current trends in surveillance and antimicrobial resistance for the Campylobacter strains involved. At the Epsom and St Helier's University Hospital (ESTH), we noted a marked increase in Campylobacter bacteraemia infections in 2021. METHODS: We extracted Campylobacter reports using the UK Health Security Agency's (UKHSA) Second Generation Surveillance System (laboratory reporting system) between 1st January 2012 and 31st December 2021. We reviewed patient records of patients with Campylobacter bacteraemia for details including presentation, past medical history, duration of hospital stay, and antibiotic use. RESULTS: Between 2012 and 2021, ESTH reported a total of 34 cases of Campylobacter bacteraemia. In 2021, the estimated incidence was 6.8 cases per 100,000 population and in the surrounding area, the incidence was 0.4 per 100,000 population. The incidence rate of Campylobacter bacteraemia in London and the South East region was significantly lower than ESTH (RR = 0.17, p < 0.0001). Campylobacter bacteraemia cases at ESTH reported a high number of co-morbidities (average number of comorbidities = 2.3) and had a duration of stay in hospital of a median of 7 days (IQR = 4-10 days). Campylobacter jejuni was the most commonly reported species for stool and blood Campylobacter in ESTH, London, and South East England. CONCLUSION: Campylobacter bacteraemia reports at ESTH were significantly (p < 0.001) higher than the surrounding London and South East region. While no common cause for the exceedance of Campylobacter bacteraemia has been identified, common risk factors for Campylobacter bacteraemia infection include underlying health conditions, being older, and male.

Did anonymity in self-administered questionnaires improve disclosure of sensitive information during the 2022 mpox outbreak in England? An observational study.

BACKGROUND: Between May 6, 2022, and Jan 16, 2023, 3555 mpox cases were reported in England, predominantly in gay, bisexual, and other men who have sex with men. Initially, the UK Health Security agency administered questionnaires to laboratory-detected cases via telephone calls. From June, 2022, cases were requested by text or email to complete the questionnaire online, with optional anonymous completion. To inform future approaches, we assess whether anonymity improved disclosure of sensitive information. METHODS: In this observational study we analysed questionnaire data completed by people with a laboratory-detected case of mpox. We included questionnaires that were completed from May 25, 2022, to Jan 16, 2023, and restricted them to anonymous or identifiable self-completed responses. Questionnaires with forename, surname, and birth date, or an ID emailed to participants, which therefore could link to laboratory data, were considered identifiable. Questionnaires without any personal identifiable information were considered anonymous. We compared the responses to seven sensitive risk factor or exposure questions using Pearson's χ2. FINDINGS: All 3555 people diagnosed with mpox infection in England were invited to complete the questionnaire through either phone call or web link.We obtained 1075 (30%) completed questionnaires, with a response rate decreasing from 45% in May to 20% in July 2022. We included 531 self-completed questionnaires in this analysis, of which 259 (49%) were anonymous and 272 (51%) were identifiable. The median age of participants was 39 years, with 514 (97%) men, 12 (2%) women, and five (1%) other. The largest ethnic groups were white (79%; n=422) and mixed or multiple ethnic groups (9%; n=47). Results of all seven questions were similar: 98% (n=254/259) of anonymous and 97% (n=265/272) of identifiable cases answered all seven questions, 49% (n=127) and 54% (n=147) reported a sexually transmitted infection diagnosis in the past 12 months (p=0·2), 24% (n=63) and 27% (n=73) reported ten or more sexual partners in the past 3 months (p=0·8), and 15% (n=38) and 18% (n=50) reported knowing another person with mpox infection (p=0·5), respectively. INTERPRETATION: Transitioning to self-completed questionnaires resulted in reduced uptake, although optional anonymity possibly prevented a steeper drop. Anonymity did not appear to affect reporting of sensitive information, specifically of sexual behaviours or history associated with mpox risk, which reinforces results of previous literature. Our interpretation is limited, however, by relatively low questionnaire uptake, and by only analysing reported rather than true risk. The decision to implement anonymous questionnaires should therefore weigh the potential benefits of increased uptake against the disadvantage of restricted data linkage. FUNDING: None.

Reassurance of population immunity to diphtheria in England: Results from a 2021 national serosurvey.

BACKGROUND: Diphtheria is rare in England because of an effective national immunisation schedule that includes 5 doses of a diphtheria-containing vaccine at 2, 3, 4 months, preschool and adolescent boosters. However, in recent years there has been a notable increase in cases due to Corynebacterium ulcerans among older adults and evidence of endemic transmission of C. diphtheriae (normally associated with travel to endemic countries). We aimed to update 2009 estimates of diphtheria immunity considering the evolving epidemiology. METHODS: Residual sera collected from diagnostic laboratories and general practitioners in England in 2021 were randomly selected and tested for diphtheria antibody, to estimate proportions protected per age group. Diphtheria antibody levels were defined as susceptible (<0.01 IU/mL), basic protection (0.01-0.099 IU/mL) and full protection (≥0.1 IU/mL). Immunity estimates were standardised to the England population and compared to 2009. RESULTS: Based on 3,745 residual sera tested, 89% (95%CI: 87%-90%) of the 2021 England population had at least basic diphtheria protection (vs. 90% [88%-92%] in 2009) and 50% (48%-52%) full protection (vs. 41% [38%-44%]). Higher antibody levels were observed in those aged 1 and under, 10-11, 12-15, 25-34 and 35-44 years compared to 2009. The largest proportion susceptible were observed in those aged 70+, 26% (21%-31%) vs 12% (7%-18%) in 2009. CONCLUSIONS: Basic diphtheria protection is comparable between 2021 and 2009. The increase in immunity in working age adults is likely due to the school leaver booster introduced in 1994. The current vaccination schedule is maintaining sufficient population immunity. However, we recommend clinicians remain vigilant to severe diphtheria outcomes in older adults, because of their observed susceptibility.

Local Salmonella Enteritidis restaurant outbreak investigation in England provides further evidence for eggs as source in widespread international cluster, March to April 2023.

We report a 5-single nucleotide polymorphism cluster of Salmonella Enteriditis in England, part of a global cluster of S. Enteritidis ST11. Forty-seven confirmed cases have been investigated of whom 25 were linked to a restaurant. In addition, there were 18 probable cases with restaurant exposure. Epidemiological investigations suggested eggs or chicken as the most likely cause of the outbreak but were unable to distinguish between those two food vehicles. Ongoing food chain investigations indicated links to imported eggs from Poland.

Evaluation of the Completeness and Timeliness of the Infant Pertussis Surveillance System in the Czech Republic in 2015, 2017 and 2019.

Introduction: The completeness and timeliness of the pertussis questionnaire-based enhanced surveillance system (ESS) among infants and reported pertussis data within the electronic nationwide notification system (NNS) in the years 2015, 2017 and 2019 were evaluated in a pilot study. Methods: The completeness of the variables for demographic characteristics, date of symptom onset, hospitalisation and vaccination status were assessed in both systems. Timeliness of reporting in the NNS was analysed as the interval between symptom onset and a) the date of first specimen collection (diagnostic delay), and b) the date of the Regional Public Health Authority receiving notification (notification delay). Results: A total of 121 confirmed pertussis cases were reported to the NNS in the study years, while in the ESS a total of 104 confirmed cases were reported in infants. In both systems most cases were in the age group of one completed month of life (20% versus 23%) and males (55% versus 55%). The majority of cases were hospitalised (81% versus 85%) and unvaccinated (77% versus 78%). Within the NNS, the first dose of vaccine was reported in 13 cases, the second dose in 11, and third dose in three cases. Within the NNS, 100% completeness of following variables was found: symptom onset, week and region of reporting, age, gender and place of isolation. Median diagnostic delay was nine days. Median notification delay was 18 days. Conclusions: Data completeness was high in the NNS, except for lack of vaccination data in those eligible by age. Efforts to improve the completeness of laboratory-related variables and timeliness are essential. Based on the study results, the project of improving the ESS for infants will continue with regular evaluation.

Factors associated with return of home oral fluid kits by suspected cases of measles, cohort study, London and South East of England, 2016-2018.

A testing rate for measles above 80% is required by the WHO European Region Measles Elimination strategy to verify elimination. To comply with this rate, we explored factors associated with the return of oral fluid kits (OFK) by suspected measles cases. We described the cases and conducted a mixed-effects analysis to assess the relationship between socio-demographic and public health management characteristics and the likelihood of returning an OFK to the reference laboratory. Of 3,929 cases who were sent a postal OFK, 2,513 (67%) returned the kit. Adjusting for confounding, registration with a general practitioner (GP) (aOR:1.48, 95%CI:1.23-1.76) and living in a less deprived area (aOR:1.35, 95%CI:1.04-1.74) were associated with an increased likelihood of returning the OFK. The odds of returning the OFK also increased if the HPT contacted the parents/guardians of all cases prior to sending the kit and confirmed their address (aOR:2.01, 95%CI:1.17-3.42). Cases notified by a hospital (aOR:1.94, 95%CI:1.31-2.87) or GP (aOR:1.52; 95%CI:1.06-2.16) also had higher odds of returning the OFK. HPTs may want to consider these factors when managing suspected cases of measles since this may help in increasing the testing rates to the WHO-recommended level.

Two Outbreaks of Foodborne Gastrointestinal Infection Linked to Consumption of Imported Melons, United Kingdom, March to August 2021.

The aim of this study was to describe two foodborne outbreaks caused by contaminated imported melon and make recommendations for future practice. Between March and July 2021, there was an outbreak of 113 cases of Salmonella Braenderup in the UK (62% female, median age 61 years, 33% hospitalized). Analytical epidemiological studies identified Galia melons as the vehicle of infection (OR 671.9, 95% CI 39.0-58,074.0, p < 0.001). Subsequently, the outbreak strain was isolated from two samples of Galia melon imported from Latin America. In July and August 2021, there was an outbreak of 17 cases of Shiga toxin-producing Escherichia coli (STEC) O157:H7 in the UK (53% female, median age 21 years, 35% were hospitalized). Review of the STEC surveillance questionnaire data, followed by the analysis of responses from a modified hypothesis-generating questionnaire, implicated eating precut watermelon from retailer B sourced from Europe as the vehicle of infection. Outbreaks of gastrointestinal pathogens caused by contaminated food of nonanimal origin are a global public health concern. Given the difficulty in removing pathogens from the flesh of ready-to-eat fruit and vegetables, public health interventions should target all steps of the food chain prior to consumption, from cultivation on the farm to processing/packing and distribution.

Prevalence and temporal dynamics of Cryptosporidium spp., Giardia duodenalis, and Blastocystis sp. among toddlers attending day-care centres in Spain. A prospective molecular-based longitudinal study.

Giardia duodenalis, Cryptosporidium spp., and Blastocystis sp. are common intestinal eukaryotic parasites affecting children in developed and resource-limited countries. Lack of information on the epidemiology and long-term stability in asymptomatic children complicates interpretation of transmission and pathogenesis. To assess the occurrence, genetic diversity, and temporal dynamics of intestinal eukaryotic parasites in young children, 679 stool samples from 125 toddlers attending six public day-care centres in Central Spain were collected bimonthly within a 1-year period. Detection and identification of species/genotypes were based on PCR and Sanger sequencing methods. Four eukaryotic species were identified: G. duodenalis (2.5‒31.6%), Cryptosporidium spp. (0.0‒2.4%), Blastocystis sp. (2.5‒6.4%), and Entamoeba dispar (0.0‒0.9%). Entamoeba histolytica and Enterocytozoon bieneusi were undetected. Sequence analyses identified assemblage A (63.6%) and B (36.4%) within G. duodenalis (n = 11), C. hominis (40%), C. parvum (40%), and C. wrairi (20%) within Cryptosporidium spp. (n = 5), and ST1 (3.8%), ST2 (46.2%), ST3 (15.4%), and ST4 (34.6%) within Blastocystis sp. (n = 26). Giardia duodenalis sub-assemblage AII/AIII was detected in a toddler for 10 consecutive months. Stable carriage of Blastocystis ST2 allele 9, ST3 allele 34, and ST4 allele 42 was demonstrated in five toddlers for up to 1 year.   Conclusions: Giardia duodenalis and Blastocystis sp. were common in toddlers attending day-care centres in Central Spain. Long-term infection/colonization periods by the same genetic variant were observed for G. duodenalis (up to 10 months) and Blastocystis sp. (up to 12 months). What is Known: • Asymptomatic carriage of G. duodenalis and Blastocystis sp. is frequent in toddlers. • The epidemiology and long-term stability of these eukaryotes in asymptomatic young children is poorly understood. What is New: • Long-term colonization/infection periods by the same genetic variant were described for Blastocystis sp. (up to 12 months) and G. duodenalis (up to 10 months).

Epidemiology of Early Monkeypox Virus Transmission in Sexual Networks of Gay and Bisexual Men, England, 2022.

After community transmission of monkeypox virus was identified in Europe, interviews of 45 case-patients from England indicated transmission in international sexual networks of gay and bisexual men since April 2022. Interventions targeting sex-on-premises venues, geospatial dating applications, and sexual health services are likely to be critical for outbreak control.

Community transmission of monkeypox in the United Kingdom, April to May 2022.

Between 7 and 25 May, 86 monkeypox cases were confirmed in the United Kingdom (UK). Only one case is known to have travelled to a monkeypox virus (MPXV) endemic country. Seventy-nine cases with information were male and 66 reported being gay, bisexual, or other men who have sex with men. This is the first reported sustained MPXV transmission in the UK, with human-to-human transmission through close contacts, including in sexual networks. Improving case ascertainment and onward-transmission preventive measures are ongoing.

Invasive Group A Streptococcus Outbreaks Associated with Home Healthcare, England, 2018-2019.

Healthcare-associated invasive group A Streptococcus (iGAS) outbreaks are common worldwide, but only England has reported outbreaks associated with home healthcare (HHC). We describe 10 outbreaks during 2018-2019 in England. A total of 96 iGAS cases (range 2-39 per outbreak) and 28 deaths (case-fatality rate 29%) occurred. Outbreak duration ranged from 3-517 days; median time between sequential cases was 20.5 days (range 1-225 days). Outbreak identification was difficult, but emm typing and whole-genome sequencing improved detection. Network analyses indicated multiple potential transmission routes. Screening of 366 HHC workers from 9 outbreaks identified group A Streptococcus carriage in just 1 worker. Outbreak control required multiple interventions, including improved infection control, equipment decontamination, and antimicrobial prophylaxis for staff. Transmission routes and effective interventions are not yet clear, and iGAS outbreaks likely are underrecognized. To improve patient safety and reduce deaths, public health agencies should be aware of HHC-associated iGAS.

Experience of using a regional network of hospitals in the care of older inpatients with COVID-19 in spring 2020.

Introduction: Frail, older patients with COVID-19 have an increased risk of hospital admission and death. Methods: We studied a regional model of care used for older patients with COVID-19 in spring 2020 across three settings: an acute teaching hospital, a district general hospital and a temporary emergency hospital. We also studied demographic and outcome data for these patients. Results: Increasing bed capacity in non-acute sites freed up beds in acute hospitals. Strict admission criteria and multidisciplinary team involvement allowed for the safe delivery of care in step-down sites. Conclusion: This model of care allowed for patient flow out of acute sites following the acute stage of their illness allowing for an increase in bed capacity while providing a safe setting for ongoing management.

VirA+EmiC project: Evaluating real-world effectiveness and sustainability of integrated routine opportunistic hepatitis B and C testing in a large urban emergency department.

Innovative testing approaches and care pathways are required to meet global hepatitis B virus (HBV) and hepatitis C virus (HCV) elimination goals. Routine blood-borne virus (BBV) testing in emergency departments (EDs) in high-prevalence areas is suggested by the European Centre for Disease Prevention and Control (ECDC) but there is limited evidence for this. Universal HIV testing in our ED according to UK guidance has been operational since 2015. We conducted a real-world service evaluation of a modified electronic patient record (EPR) system to include opportunistic opt-out HBV/reflex-HCV tests for any routine blood test orders for ED attendees aged ≥16 years. Reactive laboratory results were communicated directly to specialist clinical teams. Our model for contacting patients requiring linkage to care (new diagnoses/known but disengaged) evolved from initially primarily hospital-led to collaborating with regional health and community service networks. Over 11 months, 81,088 patients attended the ED; 36,865 (45.5%) had a blood test. Overall uptake for both HBV and HCV testing was 75%. Seroprevalence was 0.9% for hepatitis B surface antigen (HBsAg) and 0.9% for HCV antigen (HCV-Ag). 79% of 140 successfully contacted HBsAg+patients required linkage to care, of which 87% engaged. 76% of 130 contactable HCV-Ag+patients required linkage, 52% engaged. Our results demonstrate effectiveness and sustainability of universal ED EPR opt-out HBV/HCV testing combined with comprehensive linkage to care pathways, allowing care provision particularly for marginalized at-risk groups with limited healthcare access. The findings support the ECDC BBV testing guidance and may inform future UK hepatitis testing guidance.

Levels and genotypes of Salmonella and levels of Escherichia coli in frozen ready-to-cook chicken and turkey products in England tested in 2020 in relation to an outbreak of S. Enteritidis.

Frozen reformulated (FR) breaded chicken products have previously been implicated in causing human salmonellosis. A multi-country Salmonella enterica serovar Enteritidis outbreak involving several strains with >400 reported human cases in the UK occurred in 2020. Initially S. Infantis was detected in one sample from a case home but S. Enteritidis was then also isolated using a S. Enteritidis specific PCR in combination with isolation via a Craigie-tube. This prompted a survey to examine the presence and levels of Salmonella and E. coli in ready-to-cook FR poultry products in England in 2020. From a total of 483 samples, including two from cases' homes, Salmonella was detected in 42 chicken samples, these originated from six out of 53 production plants recorded. Salmonella detection was associated with elevated levels of generic E. coli (OR = 6.63). S. Enteritidis was detected in 17 samples, S. Infantis in 25, S. Newport in four and S. Java, S. Livingstone and S. Senftenberg in one each. The highest levels of Salmonella were 54 MPN/g for S. Infantis and 28 MPN/g for S. Enteritidis; 60% of the Salmonella-positive samples had <1.0 MPN/g. S. Enteritidis was detected together with S. Infantis in five samples and with S. Livingstone in one. Where S. Enteritidis was detected with other Salmonella, the former was present at between 2 and 100-fold lower concentrations. The Salmonella contamination was homogeneously distributed amongst chicken pieces from a single pack and present in both the outer coating and inner content. The S. Enteritidis were all outbreak strains and detected in six products that were linked to four production plants which implicated a Polish origin of contamination. Despite S. Infantis being most prevalent in these products, S. Infantis from only two contemporaneous human cases in the UK fell into the same cluster as isolates detected in one product. Except for one human case falling into the same cluster as one of the S. Newport strains from the chicken, no further isolates from human cases fell into clusters with any of the other serovars detected in the chicken samples. This study found that higher E. coli levels indicated a higher probability of Salmonella contamination in FR chicken products. The results also highlight the importance of recognising co-contamination of foods with multiple Salmonella types and has provided essential information for detecting and understanding outbreaks where multiple strains are involved.

Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) nosocomial transmission dynamics, a retrospective cohort study of two healthcare-associated coronavirus disease 2019 (COVID-19) clusters in a district hospital in England during March and April 2020.

OBJECTIVE: To understand the transmission dynamics of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) in a hospital outbreak to inform infection control actions. DESIGN: Retrospective cohort study. SETTING: General medical and elderly inpatient wards in a hospital in England. METHODS: Coronavirus disease 2019 (COVID-19) patients were classified as community or healthcare associated by time from admission to onset or positivity using European Centre for Disease Prevention and Control definitions. COVID-19 symptoms were classified as asymptomatic, nonrespiratory, or respiratory. Infectiousness was calculated from 2 days prior to 14 days after symptom onset or positive test. Cases were defined as healthcare-associated COVID-19 when infection was acquired from the wards under investigation. COVID-19 exposures were calculated based on symptoms and bed proximity to an infectious patient. Risk ratios and adjusted odds ratios (aORs) were calculated from univariable and multivariable logistic regression. RESULTS: Of 153 patients, 65 were COVID-19 patients and 45 of these were healthcare-associated cases. Exposure to a COVID-19 patient with respiratory symptoms was associated with healthcare-associated infection irrespective of proximity (aOR, 3.81; 95% CI, 1.6.3-8.87). Nonrespiratory exposure was only significant within 2.5 m (aOR, 5.21; 95% CI, 1.15-23.48). A small increase in risk ratio was observed for exposure to a respiratory patient for >1 day compared to 1 day from 2.04 (95% CI, 0.99-4.22) to 2.36 (95% CI, 1.44-3.88). CONCLUSIONS: Respiratory exposure anywhere within a 4-bed bay was a risk, whereas nonrespiratory exposure required bed distance ≤2.5 m. Standard infection control measures required beds to be >2 m apart. Our findings suggest that this may be insufficient to stop SARS-CoV-2 transmission. We recommend improving cohorting and further studies into bed distance and transmission factors.

Risk of COVID-19 in Health Professionals: A Case-Control Study, Portugal.

Introduction: Health professionals face higher occupational exposure to SARS-CoV-2. We aimed to estimate the risk of COVID-19 test positivity in health professionals compared to non-health professionals. Methods: We conducted a test-negative case-control study using Portuguese national surveillance data (January to May 2020). Cases were suspected cases who tested positive for SARS-CoV-2; controls were suspected cases who tested negative. We used multivariable logistic regression modelling to estimate the odds ratio of a positive COVID-19 test (RT-PCR; primary outcome), comparing health professionals and non-health professionals (primary exposure), and adjusting for the confounding effect of demographic, clinical, and epidemiological characteristics, and the modification effect of the self-reported epidemiological link (i.e., self-reported contact with a COVID-19 case or person with COVID-19-like symptoms). Results: Health professionals had a 2-fold higher risk of a positive COVID-19 test result (aOR = 1.89, 95% CI 1.69-2.11). However, this association was strongly modified by the self-report of an epidemiological link such that, among cases who did report an epidemiological link, being a health professional was a protective factor (aOR = 0.90, 95% CI 0.82-0.98). Conclusion: Our findings suggest that health professionals might be primarily infected by unknown contacts, plausibly in the healthcare setting, but also that their occupational exposure does not systematically translate into a higher risk of transmission. We suggest that this could be interpreted in light of different types and timing of exposure, and variability in risk perception and associated preventive behaviours.

Introdução: Os profissionais de saúde têm uma maior exposição profissional à SARS-CoV-2. O objetivo era estimar o risco de testar positivo para SARS-CoV-2 em profissionais de saúde. Métodos: Foi realizado um estudo testenegativo caso-controlo utilizando os dados de vigilância epidemiológica nacional (Janeiro­Maio 2020). Casos foram definidos como casos suspeitos que testaram positivo para SARS-CoV-2 (RTPCR), e os controlos como casos suspeitos que testaram negativo. Foi aplicado um modelo de regressão logística multivariável para estimar o odds ratio de teste positivo para SARS-CoV-2, comparando profissionais de saúde e não profissionais de saúde, ajustado para as características demográficas, clínicas e epidemiológicas, e a modificação de efeito com o autorrelato duma ligação epidemiológica (i.e., contacto auto-reportado com um caso COVID-19 ou uma pessoa com sintomas semelhantes aos da COVID-19). Resultados: Os profissionais de saúde tiveram um risco duas vezes maior de testar positivo para SARS-CoV-2 (aOR = 1.89, 95% CI 1.69­2.11). No entanto, esta associação era fortemente modificada pelo autorrelato de uma ligação epidemiológica, de tal forma que entre os casos que relataram uma ligação epidemiológica, ser profissional de saúde revelou-se fator de proteção (aOR = 0.90, 95% CI 0.82­0.98). Conclusão: Os nossos resultados sugerem que os profissionais de saúde podem estar infetados principalmente por contactos desconhecidos, plausivelmente em instituições de saúde, e a exposição profissional não se traduz sistematicamente num maior risco de transmissão. Isto poderá ser interpretado à luz de diferentes tipos e tempos de exposição, e da variabilidade na perceção do risco e dos comportamentos preventivos associados.