A groundbreaking study from Australia's CSIRO reveals that SARS-CoV-2 can persist up to 28 days on smooth surfaces in dark, room-temperature conditions. Leading experts offer important caveats on real-world applicability.
As global COVID-19 cases rise, scientists are intensifying research on SARS-CoV-2 to uncover its transmission dynamics. Beyond droplets from coughs and sneezes, the virus spreads via fine respiratory aerosols that linger in the air. But surfaces play a role too, prompting closer scrutiny of fomite transmission.
CSIRO researchers simulated real-world conditions by suspending a high-titer strain of SARS-CoV-2 (concentration: 4.97 × 107/ml, akin to peak viral loads in infected patients) in artificial mucus. They applied it to stainless steel, glass (like phone screens), vinyl, cotton, polymer banknotes, and paper towels, then tested at 20°C, 30°C, and 40°C in darkness. Samples were collected at 1 hour, 1, 3, 7, 14, 21, and 28 days.
Results showed SARS-CoV-2 viable for 28 days on glass, stainless steel, and polymer banknotes at 20°C, dropping to 7 days at 30°C and 24 hours at 40°C. Porous cotton limited survival to 14 days at 20°C and under 16 hours at 40°C.
This extends prior findings of 3-day survival on non-porous surfaces. "For context, influenza A viruses last 17 days in similar tests, underscoring SARS-CoV-2's resilience," notes co-author Debbie Eagles, PhD.
CSIRO's Trevor Drew, director of the Australian Centre for Disease Preparedness, urges caution. The study used peak viral loads without UV light exposure, which naturally degrades the virus. Post-28 days, infectivity was significantly reduced from initial levels—though sufficient for transmission remains unclear.
Ron Eccles, professor of respiratory pharmacology at Cardiff University, echoes this, noting artificial mucus lacks enzymes that degrade viruses in real samples. He warns against "unnecessary fear," estimating infectious viruses persist just hours in practice.
Eagles counters that while surface transmission details need more study, understanding viability is vital for high-contact risk mitigation strategies.
