Nosocomial transmission of respiratory syncytial virus in an outpatient cancer center

Abstract

Respiratory syncytial virus (RSV) outbreaks in inpatient settings are associated with poor outcomes in cancer patients. The use of molecular epidemiology to document RSV transmission in the outpatient setting has not been well described. We performed a retrospective cohort study of 2 nosocomial outbreaks of RSV at the Seattle Cancer Care Alliance. Subjects included patients seen at the Seattle Cancer Care Alliance with RSV detected in 2 outbreaks in 2007-2008 and 2012 and all employees with respiratory viruses detected in the 2007-2008 outbreak. A subset of samples was sequenced using semi-nested PCR targeting the RSV attachment glycoprotein coding region. Fifty-one cases of RSV were identified in 2007-2008. Clustering of identical viral strains was detected in 10 of 15 patients (67%) with RSV sequenced from 2007 to 2008. As part of a multimodal infection control strategy implemented as a response to the outbreak, symptomatic employees had nasal washes collected. Of 254 employee samples, 91 (34%) tested positive for a respiratory virus, including 14 with RSV. In another RSV outbreak in 2012, 24 cases of RSV were identified; 9 of 10 patients (90%) had the same viral strain, and 1 (10%) had another viral strain. We document spread of clonal strains within an outpatient cancer care setting. Infection control interventions should be implemented in outpatient, as well as inpatient, settings to reduce person-to-person transmission and limit progression of RSV outbreaks.

Keywords: Health care worker; Infection control; Molecular epidemiology; Outpatient clinic; Respiratory syncytial virus.

Figure 1

Histogram of all RSV cases at the SCCA per day in the 2007-2008 outbreak (A) and only cases where the viral strain was sequenced (B). Histogram of all RSV cases at the SCCA per day in the 2012 outbreak (C) and only cases where the viral strain was sequenced (D). The asterisk represents an identical viral strain for that season. The pattern of the box represents the team of providers seen by the patient.

Figure 2

Our Respiratory Virus Management Plan was implemented January 1, 2008 and included designation of 3 tiers of heightened respiratory viral surveillance and infection control strategies.

Figure 3

Chart of RSV cases per day during the outbreak as compared with numbers of patients seen and numbers of community RSV cases in the Pacific Northwest Region for the (A) 2007-2008 season and (B) 2011-2012 season. The bars represent the numbers of RSV-positive cases at the SCCA clinic. The dotted line represents the number of patients (in multiples of 1000) seen at the SCCA clinic. The dashed line represents the numbers of community cases in the Pacific Northwest.

Figure 4

Phylogenetic trees were constructed using sequenced samples from the 2 outbreaks. The outbreak strains are identified by year followed by provider team. The reference and community strains are labeled with year followed by reference strain (RS) or community strain (CS). The numbers at the nodes are the bootstrap values. This phylogenetic tree shows the sequenced samples from the 2007-2008 outbreak. Of the 15 outbreak strains, 14 were subtype A and 1 was subtype B. The tree with the highest log likelihood (–1047.02) is shown. Community samples were collected during RSV season in the Seattle region from November to April from inpatients at Seattle Children's Hospital and the University of Washington, as well as community childcare attendees.

Figure 5

Phylogenetic trees were constructed using sequenced samples from the 2 outbreaks. The outbreak strains are identified by year followed by provider team. The reference and community strains are labeled with year followed by reference strain (RS) or community strain (CS). The numbers at the nodes are the bootstrap values. This phylogenetic tree shows the sequenced samples from the 2012 outbreak. Of the 10 outbreak strains, 9 were subtype A and 1 was subtype B. The tree with the highest log likelihood (–905.54) outbreak is shown. Community samples were collected during RSV season in the Seattle region from November to April from inpatients at Seattle Children's Hospital and the University of Washington, as well as community childcare attendees.