Virus Survival on Surfaces May be Affected by Temperature and Humidity

The SARS coronavirus (CoV) may survive on surfaces for days at temperature and humidity levels common to indoor environments say researchers from the University of North Carolina at Chapel Hill. They report their findings in the May 2010 issue of the journal Applied and Environmental Microbiology.

During the worldwide outbreak of SARS-CoV in 2003 hospital surfaces were examined for their role in the spread of the virus following large numbers of cases being reported in health care workers, patients, and visitors to health care facilities. Surface sampling revealed SARS-CoV on surfaces and inanimate objects suggesting a possible source of transmission. The role that environmental factors, such as air temperature and relative humidity play in surface survival is important for risk assessment and the development of control measures.

Considered a biosafety hazard, only specially trained personnel are permitted to work with SARS-CoV under strict laboratory containment conditions. Two surrogate animal coronaviruses, transmissible gastroenteritis virus (TGEV) and mouse hepatitis virus (MHV), were studied at various temperature and humidity levels to determine their survival rate on stainless steel. Inactivation of the virus occurred most rapidly at extremely hot temperatures and high humidity levels. When exposed to temperature and humidity levels more typical of indoor environments, the viruses could persist on surfaces for up to 28 days.

"When high numbers of viruses are deposited, TGEV and MHV may survive for days on surfaces at air temperatures and relative humidity typical of indoor environments," say the researchers. "TGEV and MHV could serve as conservative surrogates for modeling exposure, the risk of transmission, and control measures for pathogenic enveloped viruses, such as SARS-CoV and influenza virus, on healthcare surfaces."

Reference: L.M. Casanova, S. Jeon, W.A. Rutala, D.J. Weber, M.D. Sobsey. 2010. Effects of air temperature and relative humidity on coronavirus survival on surfaces. Applied and Environmental Microbiology, 76. 9: 2712-2717.