Influenza virus emitted by naturally-infected hosts in a healthcare setting

Highlights • This pilot study examined the viral content of bioaerosols emitted by patients with laboratory-confirmed influenza. • Nine out of fifteen patients emitted variable amounts of viral RNA. • Patients with influenza may emit virus into the air which disperses >1 m and may reach the breathing zone of a healthcare worker.
Background The emergence of novel respiratory viruses such as avian influenza A(H7N9) virus and the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) highlights the importance of understanding determinants of transmission to healthcare workers (HCWs) and the public. Objectives We aim to determine the viral content of the air emitted by symptomatic inpatients or long-term care residents with laboratory-confirmed influenza virus infection (emitters), and in the breathing zones of healthcare workers who attend to them. Design A prospective pilot study of patients with laboratory-confirmed influenza virus infection was undertaken. Air within 1 m of the patient was sampled using a high volume air sampler. In addition, a lower volume air sampler was placed 1 m from the patient. Viral RNA was recovered from the samplers and submitted for quantitative real time PCR. In addition, personal button samplers were provided to HCWs. Results The air emitted by 15 participants with laboratory-confirmed influenza virus infection was sampled. Of the patients infected with influenza A, viral RNA was recovered from the air emitted by 9/12 patients using the low-volume sampler; no viral RNA was detected from air emitted by patients with influenza B (n = 3). Influenza virus RNA was recovered from one HCW’s sampler. Conclusions Patients with respiratory virus infection emit virus into the air which disperses to >1 m and may reach the breathing zone of a HCW. This pilot study highlights the feasibility and importance of conducting a larger-scale study to identify determinants of exposure and transmission from patient to HCW.