Transmission dynamics and associated mortality of nosocomial COVID-19 throughout 2021: a retrospective study at a large teaching hospital in London.

BACKGROUND: The impact of nosocomial SARS-CoV-2 infections has changed significantly since 2020. However, there is a lack of up-to-date evidence of the epidemiology of these infections which is essential in order to appropriately guide infection control policy. AIMS: To identify the secondary attack rate of SARS-CoV-2 infection and associated mortality across different variants of concern. METHODS: A single-centre retrospective study of all nosocomial SARS-CoV-2 exposure events was conducted between 31st December 2020 and 31st December 2021. A secondary attack rate was calculated for nosocomial acquisition of SARS-CoV-2 infection and time to positivity. Positive contacts were assessed for all-cause 30-day mortality. RESULTS: A total of 346 sequential index exposure events were examined, and 1378 susceptible contacts identified. Two hundred susceptible contacts developed SARS-CoV-2 infection (secondary attack rate of 15.5%). The majority of index cases (59%) did not result in any secondary SARS-CoV-2 infection. Where close contacts developed SARS-CoV-2 infection, 80% were detected within the first five days since last contact with the index case. The overall associated mortality among positive contacts across 2021 was 9%, with an estimated reduction of 68% when comparing periods of high Omicron versus Alpha transmission. CONCLUSION: Our findings describe that most SARS-CoV-2 infections are detected within five days of contact with an index case; we have also demonstrated a considerably lower mortality rate with the Omicron variant in comparison to previous variants. These findings have important implications for informing and supporting infection control protocols to allow movement through the hospital, and ensure patients access care safely.

Human parainfluenza virus type 3 infections in a haemato-oncology unit: social distancing measures needed in outpatient clinics.

BACKGROUND: Human parainfluenza virus type 3 (HPIV3) infections are associated with high mortality in immunocompromised settings, especially in bone marrow transplant recipients. Asymptomatic infection and lack of effective antiviral treatment makes HPIV3 prevention and treatment a real challenge. AIM: To retrospectively investigate the epidemiological characteristics, clinical characteristics and outcomes of 51 haematology patients with confirmed HPIV3 infections, detected between February and May 2019 in the haematology unit at King's College Hospital, London. METHODS: Between February and May 2019, HPIV3 RNA was detected in combined nose and throat swab samples collected from 51 symptomatic haematology patients, 41 of whom attended the haematology outpatient unit. Clinical data were reviewed retrospectively and a timeline of patients' appointments drawn up to investigate transmission. Sequencing analysis was performed on 14 stored samples. FINDINGS: Fifty-one patients were identified with HPIV3 infection. Mean age was 54 years (SD: 12; range: 19-72) and 60% (31/51) were male. There were 41 (80%) bone marrow transplant recipients, 24 had an allograft, and 17 an autograft. Thirty-day and 3-month mortality post HPIV3 was 6% and 14%, respectively. Lower respiratory tract infection and inpatient acquisition were associated with higher mortality (6/7 vs 1/7, P = 0.010; and 5/7 vs 2/7, P = 0.031). Onset of HPIV3 infection in patients within 6 days of attending the clinic was associated with the clusters identified in phylogenetic analysis (64% (9/14) vs 21% (8/37); odds ratio: 6.5 (confidence interval: 95% 1.7-25); P = 0.006). CONCLUSION: Timelines suggested community transmission, but also possible transmission patterns within the outpatients and subsequent nosocomial transmission within the same ward. Early recognition of HPIV3 infection and the use of polymerase chain reaction and sequence analysis is fundamental in identifying respiratory virus outbreaks and person-to-person transmission. Careful planning of outpatient clinic attendance is required to minimize contact and prevent respiratory virus transmission in immunosuppressed patients.

Factors influencing antimicrobial prescription attitudes in bloodstream infections: susceptibility results and beyond. An exploratory survey.

BACKGROUND: Novel rapid antimicrobial susceptibility testing (RAST) methods promise quicker de-escalation of broad-spectrum antibiotics. However, other behavioural and situational factors influencing antimicrobial prescription are not well known. AIM: To explore factors associated with optimal antimicrobial prescription in patients with Gram-negative bloodstream infection and to propose specific scenarios in which a rapid antimicrobial susceptibility result may help to optimize prescribing. METHODS: Exploratory survey (April-August 2018) in the UK and Spain using clinical case-related questions. Seniority, specialty and country of practice were recorded. Cases described patients with Gram-negative bloodstream infections, their empirical treatment and clinical course and the hypothetical RAST result. Respondents chose one of several options regarding antibiotic treatment management. Microbiologically optimal antibiotic choice (MOAC) was agreed by expert consensus beforehand. Responses were categorized as MOAC, request for support or sub-optimal choice. The relationship between the RAST result and the clinical course was defined as concordant (susceptible organism-clinical improvement; resistant organism-clinical deterioration) or as discordant otherwise. FINDINGS: A total of 426 respondents (UK: 332; Spain: 94) and 1494 answers were analysed. Multivariate analysis identified that requests for support were 87% less likely in Spain; that antimicrobial resistance and clinical deterioration were associated with both increased request for support (odds ratio (OR) 7.66 and OR 4.26, respectively) and MOAC (OR 2.08 and OR 2.06, respectively). A discordant clinical course was associated with 82% lower odds for MOAC. Out-of-hours results, seniority and specialty did not have an effect. CONCLUSION: Antimicrobial choice is influenced by each country's type of practice, clinical course and susceptibility results. Antimicrobial resistance was associated with increased optimal treatment, suggesting RAST may be less useful for step-down decisions in settings with low baseline resistance rates.