A Cluster of 2009 Pandemic Influenza A (H1N1) in Patients and Healthcare Providers in a Hematology Oncology Unit

Background:  

Unsuspected cases of influenza in patients or healthcare providers (HCP) working with influenza pose the greatest risk for transmission of influenza within the hospital.

Objective:

To describe an outbreak of influenza A in a hematology/oncology unit during the summer of 2009.

Index Patient:

The index case (patient X) was a 69 year old man with leukemia, who was admitted a week after chemotherapy with neutropenic fever, cough, and a clear chest radiograph. He tested positive for influenza A on hospital day 4 with subsequent respiratory failure requiring intubation. Shortly thereafter multiple HCP became ill and were working while symptomatic.

Methods:

All HCP with symptoms consistent with an ILI were tested for influenza and sent home.  A list of potentially exposed patients and HCP was generated.  A definitive nosocomial case was defined as onset of influenza-like illness (ILI) ≥ 48 hours after admission with a positive test for influenza A during the outbreak period (6/30/09 to 7/6/09). A probable case was defined as ILI during the outbreak period.  All on site influenza testing was done using a real-time PCR assay.  Confirmatory testing for H1N1 was performed by Ohio Department of Health. An ad hoc occupational health clinic was established to manage HCP exposure risk assessment and provide oseltamivir prophylaxis when indicated. Subsequently, the sick leave policy removed penalizing points for ILI and an occupational health hotline was established to manage HCP work restrictions.

Results:

See epidemic curve. The roommate of Patient X and another patient on the unit tested positive for influenza A. Seven HCP on the unit had ILI; 4 of whom were tested and were positive for influenza A.   All patients on the unit during the outbreak period received oseltamivir prophylaxis as well as 47% (56/120) of HCP with face-to-face exposure and/or worked on the unit during the outbreak period. No additional cases of ILI were identified among patients or HCP on the unit. Influenza A Isolates from the three patients and one HCP were confirmed to be pandemic 2009 H1N1.

Conclusions:  

We describe a cluster of nosocomial H1N1 influenza on a hematology oncology unit early in the pandemic.  Further nosocomial spread was prevented by removal of sick HCP from the workplace and targeted use of oseltamivir prophylaxis.  Preventing nosocomial spread of influenza in a non-vaccinated population requires administrative processes that include recognition of potential cases, a low threshold for testing and isolating patients, rapid identification and removal of ill HCP, and consideration of targeted prophylaxis. Institutions may wish to consider a review of sick leave polices and cultural norms that may encourage some clinicians to work when sick.