Persistence of the 2009 pandemic influenza a (H1N1) virus on N95 respirators

Abstract

In the United States, the 2009 pandemic influenza A (H1N1) virus (pH1N1) infected almost 20% of the population and caused >200,000 hospitalizations and>10,000 deaths from April 2009 to April 2010. On 24 April 2009, the CDC posted interim guidance on infection control measures in health care settings explicitly for pH1N1 and recommended using filtering face respirators (FFRs) when in close contact with a suspected- or confirmed-to-be-infected individual, particularly when performing aerosolgenerating procedures. The persistence and infectivity of pH1N1 were evaluated on FFRs, specifically N95 respirators, under various conditions of absolute humidity (AH) (4.1×105 mPa, 6.5×105 mPa, and 14.6×105 mPa), sample matrices (2% fetal bovine serum [FBS], 5 mg/ml mucin, and viral medium), and times (4, 12, 24, 48, 72, and 144 h). pH1N1 was distributed onto N95 coupons (3.8 to 4.2 cm2) and extracted by a vortex-centrifugation-filtration process, and the ability of the remaining virus to replicate was quantified using an enzyme-linked immunosorbent assay (ELISA) to determine the log10 concentration of the infectious virus per coupon. Overall, pH1N1 remained infectious for 6 days, with an approximately 1-log10 loss of virus concentrations over this time period. Time and AH both affected virus survival. We found significantly higher (P<0.01) reductions in virus concentrations at time points beyond 24 to 72 h (-0.52-log10 reduction) and 144 h (-0.74) at AHs of 6.5×105 mPa (-0.53) and 14.6×105 mPa (-0.47). This research supports discarding respirators after close contact with a person with suspected or confirmed influenza infection due to the virus's demonstrated ability to persist and remain infectious. © 2013, American Society for Microbiology.