Persistence of Influenza A (H1N1) Virus on Stainless Steel Surfaces.

UNLABELLED: As annual influenza epidemics continue to cause significant morbidity and economic burden, an understanding of viral persistence and transmission is critical for public health officials and health care workers to better protect patients and their family members from infection. The infectivity and persistence of two influenza A (H1N1) virus strains (A/New Caledonia/20/1999 and A/Brisbane/59/2007) on stainless steel (SS) surfaces were evaluated using three different surface matrices (2% fetal bovine serum, 5 mg/ml mucin, and viral medium) under various absolute humidity conditions (4.1 × 10(5) mPa, 6.5 × 10(5) mPa, 7.1 × 10(5) mPa, 11.4 × 10(5) mPa, 11.2 × 10(5) mPa, and 17.9 × 10(5) mPa) for up to 7 days. Influenza A virus was deposited onto SS coupons (7.07 cm(2)) and recovered by agitation and sonication in viral medium. Viral persistence was quantified using a tissue culture-based enzyme-linked immunosorbent assay (ELISA) to determine the median (50%) tissue culture infective dose (TCID50) of infectious virus per coupon. Overall, both strains of influenza A virus remained infectious on SS coupons, with an approximate 2 log10 loss over 7 days. Factors that influenced viral persistence included absolute humidity, strain-absolute humidity interaction, and time (P ≤ 0.01). Further studies on the transfer of influenza A virus from fomites by hand and the impact of inanimate surface contamination on transmission should be performed, as this study demonstrates prolonged persistence on nonporous surfaces. IMPORTANCE: This study tested the ability of two influenza A (H1N1) virus strains to persist and remain infectious on stainless steel surfaces under various environmental conditions. It demonstrated that influenza A (H1N1) viruses can persist and remain infectious on stainless steel surfaces for 7 days. Additional studies should be conducted to assess the role played by contaminated surfaces in the transmission of influenza A virus.

MS2 Coliphage as a Surrogate for 2009 Pandemic Influenza A (H1N1) Virus (pH1N1) in Surface Survival Studies on N95 Filtering Facepiece Respirators.

Research on influenza viruses regarding transmission and survival has surged in the recent years due to infectious emerging strains and outbreaks such as the 2009 Influenza A (H1N1) pandemic. MS2 coliphage has been applied as a surrogate for pathogenic respiratory viruses, such as influenza, as it's safe for personnel to handle and requires less time and labor to measure virus infectivity. However, direct comparisons to determine the effectiveness of coliphage as a surrogate for influenza virus regarding droplet persistence on personal protective equipment such as N95 filtering facepiece respirators (FFRs) are lacking. Persistence of viral droplets deposited on FFRs in healthcare settings is important to discern due to the potential risk of infection via indirect fomite transmission. The objective of this study was to determine if MS2 coliphage could be applied as a surrogate for influenza A viruses for studying persistence when applied to the FFRs as a droplet. The persistence of MS2 coliphage and 2009 Pandemic Influenza A (H1N1) Virus on FFR coupons in different matrices (viral media, 2% fetal bovine serum, and 5 mg ml-1 mucin) were compared over time (4, 12, 24, 48, 72, and 144 hours) in typical absolute humidity conditions (4.1 × 105 mPa [18°C/20% relative humidity (RH)]). Data revealed significant differences in viral infectivity over the 6-day period (H1N1- P <0.0001; MS2 - P <0.005), although a significant correlation of viral log10 reduction in 2% FBS (P <0.01) was illustrated. Overall, MS2 coliphage was not determined to be a sufficient surrogate for influenza A virus with respect to droplet persistence when applied to the N95 FFR as a droplet.

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

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 aerosol-generating procedures. The persistence and infectivity of pH1N1 were evaluated on FFRs, specifically N95 respirators, under various conditions of absolute humidity (AH) (4.1 × 10(5) mPa, 6.5 × 10(5) mPa, and 14.6 × 10(5) 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 cm(2)) 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 × 10(5) mPa (-0.53) and 14.6 × 10(5) 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.