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Molecular epidemiology of two consecutive outbreaks of parainfluenza 3 in a bone marrow transplant unit
1Enteric and Respiratory Virus Laboratory, Central Public Health Laboratory, London, United Kingdom. mzambon@phls.co.uk
Abstract:
Two consecutive nosocomial outbreaks of parainfluenza 3, in which 5 of 15 infected patients died, occurred in an adult bone marrow transplant unit. Parainfluenza 3 strain variation was assessed by reverse transcription-PCR sequencing of part of the parainfluenza 3 F gene, including the noncoding region, directly from clinical samples. Sequence data from the outbreaks were compared with those from 15 other parainfluenza 3 isolates circulating concurrently in the community; altogether, 13 strains which fell into three lineages were identified. Four immunosuppressed patients shed virus persistently for between 1 and 4 months without change in sequence. The first outbreak lasted 4 months and involved three parainfluenza 3 strains, and one persistently infected patient was implicated as the source of infection for three others. The second outbreak lasted for 1 month but involved only one strain. These data indicate that introduction of community parainfluenza 3 strains to the bone marrow transplant unit was followed by person-to-person transmission within the unit rather than reintroduction of virus from the community.
Insights
Nosocomial outbreaks of parainfluenza 3 in bone marrow transplant patients led to deaths. Strain analysis revealed person-to-person transmission within the unit, not reintroduction from the community.
Area of Science:
- Infectious Diseases
- Virology
- Epidemiology
Background:
- Nosocomial outbreaks of parainfluenza virus type 3 (PIV3) can cause severe illness and mortality in immunocompromised patients.
- Adult bone marrow transplant (BMT) units are particularly vulnerable to viral infections due to profound immunosuppression.
Purpose of the Study:
- To investigate the genetic diversity and transmission dynamics of parainfluenza 3 strains during two consecutive nosocomial outbreaks in an adult bone marrow transplant unit.
- To differentiate between community-acquired and hospital-acquired transmission of PIV3.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) sequencing of the PIV3 F gene from clinical samples.
- Phylogenetic analysis of outbreak strains compared to concurrent community isolates.
- Tracking of viral shedding duration and sequence stability in persistently infected patients.
Main Results:
- Two consecutive PIV3 outbreaks occurred, with 5 of 15 infected patients dying.
- Thirteen distinct PIV3 strains, falling into three lineages, were identified across the outbreaks and community isolates.
- Four immunosuppressed patients exhibited persistent viral shedding for 1-4 months without sequence variation.
- The first outbreak involved three strains over 4 months, with one persistently infected patient linked to secondary infections.
- The second outbreak involved a single strain over 1 month.
Conclusions:
- Introduction of community PIV3 strains into the BMT unit was followed by sustained person-to-person transmission within the unit.
- Persistent viral shedding in immunocompromised patients can contribute to prolonged outbreaks.
- Genomic sequencing is crucial for understanding transmission pathways and controlling nosocomial viral infections in high-risk settings.