10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Aerosol and Surface Sampling for a Novel H7N2 Influenza A Virus at a New York City Feline Quarantine Facility
WILLIAM LINDSLEY, Francoise Blachere, Angela M. Weber, Donald Beezhold, Robert Thewlis, Kenneth R. Mead, John Noti, National Institute for Occupational Safety and Health
Abstract Number: 23 Working Group: Infectious Bioaerosol
Abstract Influenza is of tremendous concern to the public health community because of the potential for new strains of the virus to cause a severe pandemic. In December 2016, an outbreak of a novel avian-lineage H7N2 influenza A virus was detected among cats in three animal shelters in New York City. H7N2 influenza had never been previously reported in cats, and further investigation found that at least one case of cat-to-human transmission to a veterinary staff member had occurred. To contain the outbreak, 500 cats that were potentially exposed to the virus were moved to a temporary feline quarantine facility and infection control measures were implemented.
In order to better understand the possible transmission pathways of the virus and the occupational exposure risk for animal shelter workers, the National Institute for Occupational Safety and Health (NIOSH) conducted aerosol and surface sampling in the quarantine facility. The quarantine facility was housed in a two-story warehouse with recirculating air heaters and natural ventilation. The animal isolation zone had a floor area of approximately 220 m2 (7800 ft2) and a ceiling height of approximately 3.7 m (12 feet). During sampling, the interior temperature was 18°C and the relative humidity was 25%.
Twenty aerosol samples were collected using NIOSH two-stage cyclone aerosol samplers with a 3.5 liter/min sampling rate for 4-5 hours. The NIOSH sampler separates aerosol particles into three size fractions (≥4 µm, 1 to 4 µm, and ≤1 µm) and conforms to the ACGIH/ISO criteria for respirable particle sampling. Sixteen aerosol samples were collected within the isolation zone, and all of these samples were positive for the H7N2 virus by RT-PCR. The mean concentration of airborne H7N2 influenza virus was 5810 viral copies/m3 of air (SD 4230). Seventy-one percent of the virus was detected in particles ≥4 µm, while 28% was found in 1-4 µm particles, and 1.4% in ≤1 µm particles. Influenza was not detected in 4 aerosol samples collected outside the isolation zone.
Thirteen aerosol samples were collected in the isolation zone using SKC BioSamplers at 12.5 liters/minute for 60 minutes. The SKC BioSampler collects particles into a liquid viral transport media, which helps preserve the viability of the virus. Sterile distilled water was added to the BioSamplers every 15 minutes as needed to replace water lost due to evaporation. Twelve of these aerosol samples were positive for H7N2 influenza by RT-PCR, with a mean airborne concentration of 3260 viral copies/m3 of air (SD 1830). Viable airborne influenza virus was detected in 6 samples.
Thirty-one surface samples were collected using sterile nylon-flocked swabs moistened with viral transport media. Of the 22 surface swabs taken in the isolation zone, 17 were positive for H7N2 influenza by RT-PCR, with a mean of 1030 viral copies/sample (SD 1890). Viable influenza virus was detected in 5 surface samples. Nine surface swabs were collected outside of the isolation zone, none of which were positive for influenza.
The results of this study show that airborne and surface H7N2 influenza virus were pervasive throughout the isolation zone of the quarantine facility, which suggests that airborne, droplet and contact transmission were all potential pathways for the spread of the virus. These results also indicate that occupational exposures to the virus could occur by all three routes, which helps inform decisions about appropriate protective measures for the animal care workers. Finally, this study illustrates the need for a prompt risk assessment of any newly-emerging pathogenic microorganism to help control disease transmission, prevent occupational exposures, and protect the public health.