Clinical and Epidemiological Insights into a Parainfluenza Virus Type 3 Outbreak in Multiple Myeloma Patients

Abstract

Human parainfluenza virus type 3 (HPIV-3) can be responsible for mild to severe respiratory infections and hospital epidemics. We investigated an outbreak in a hematology unit. Respiratory viruses were screened using multiplex PCR. HPIV-3 quantification and whole-genome sequencing were performed on HPIV-3 positive respiratory samples. Clinical characteristics, infection progression, incidence rates of respiratory viruses within the hospital and detection of respiratory viruses were documented, along with the reinforcement of infection prevention and control (IPC) measures implemented. Between November 2022, and January 2023, HPIV-3 was identified in 20 of 113 hematology patients (17.7%), of whom 80% had multiple myeloma. A majority of HPIV-3-positive patients developed pneumonia (60%), and mortality was notably higher (35%) compared to patients who were negative (3%, p < 0.0001). Respiratory HPIV-3 viral loads were similar between patients with and without pneumonia. In parallel, HPIV-3 incidence in the hospital overall was lower than in the hematology unit (p < 0.0001). Air virus screening showed the detection of HPIV-3 in the air in different areas, and whole-genome sequencing confirmed the circulation of a single HPIV-3 strain. Strengthened IPC measures were associated with the containment of the outbreak. HPIV-3 has high epidemic potential in patients with multiple myeloma and causes severe infections. Our findings highlight the need for routine HPIV-3 testing in hematology units.

Keywords: HPIV‐3; air detection; hematology; infection and prevention control; outbreak; pneumonia; viral load; whole genome sequencing.

Figure 1

Synoptic view of the detection of new HPIV‐3 cases in the hematology ward. Each square represents a newly detected patient infected with HPIV‐3. Red squares indicate patients who were symptomatic at the time of detection, orange squares indicate patients who were asymptomatic at detection but developed symptoms in the following days, and green squares indicate patients who remained asymptomatic. Striped squares represent patients whose first positive sample was sequenced. The first arrow marks when the increase in positive cases alerted the Infection Prevention and Control Unit, and the second arrow indicates when the meeting in the hematology unit took place.

Figure 2

Phylogenetic analysis of HPIV‐3 strains. Strains from hematology unit patients and four control patients from other units, meeting the predefined quality criteria, are shown in blue and green, respectively. The strain shown in red corresponds to the reference used to map the genomes (NC_001796.2). Strains in black represent publicly available sequences from GenBank (n = 172). Branches with bootstrap support of 80% or higher are marked with gray circles.