Controlling a human parainfluenza virus-3 outbreak in a haematology ward in a tertiary hospital: the importance of screening strategy and molecular diagnostics in relation to clinical symptoms

Background: The human parainfluenza virus 3 (HPIV-3) outbreak at the haemato-oncology ward of the Maastricht University Medical Centre in the summer of 2016. Aim: To describe an effective strategy to control the largest reported HPIV-3 outbreak at an adult haematology-oncology ward in the Netherlands by implementing infection control measures and molecular epidemiology investigation. Methods: Clinical, patient and diagnostic data were both pro-and retrospectively collected. HPIV-3 real-time polymerase chain reaction (HPIV-3 RT-PCR) was validated using oropharyngeal rinse samples. Screening of all new and admitted patients was implemented to identify asymptomatic infection or prolonged shedding of HPIV-3 allowing cohort isolation. Findings: The HPIV-3 outbreak occurred between 9 July and 28 September 2016 and affected 53 patients. HPIV-3 RT-PCR on oropharyngeal rinse samples demonstrated an up to 10-fold higher sensitivity compared with pharyngeal swabs. Monitoring showed that at first positive PCR, 20 patients (38%) were asymptomatic (of which 11 remained asymptomatic) and the average duration of shedding was 14 days (range 1-58). Asymptomatic patients had lower viral load, shorter period of viral shedding (<14 days) and were mostly immune-competent oncology patients. The outbreak was under control five weeks after implementation of screening of asymptomatic patients. Conclusion: Implementation of a sensitive screening method identified both symptomatic and asymptomatic patients which had lower viral loads and allowed early cohort isolation. This is especially important in a ward that combines patients with varying immune status, because both immunocompromised and immune-competent patients are likely to spread the HPIV-3 virus, either through prolonged shedding or through asymptomatic course of disease. (c) 2022 The Authors. Published by Elsevier Ltd on behalf of The Healthcare Infection Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).