A recent journal Food Microbiology study demonstrates that human coronaviruses remain stable for up to 21 days on glass surfaces. However, common dishwashing detergents and scrubbing devices were found to be sufficient to inactivate and eliminate these viruses from glass surfaces.
Study: Coronaviruses are stable on glass but are eliminated by manual dishwashing procedures. Image Credit: DG FotoStock / Shutterstock.com
Human coronaviruses include both alpha and beta coronaviruses. Of all human coronaviruses, two alpha coronaviruses including HCoV-229E and HCoV-NL-63, as well as two beta coronaviruses of HCoV-OC43 and HCoV-HKU-1, are globally endemic, causing mild respiratory infections like other common cold viruses.
The three most deadly members of the human beta coronavirus family include the severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2, the latter of which is the causative pathogen of ongoing coronavirus disease 2019 (COVID-19) pandemic.
As a respiratory virus, SARS-CoV-2 is primarily transmitted between humans through respiratory droplets and aerosols. Viral transmission from contaminated surfaces has also been observed in some cases, as some evidence suggests that SARS-CoV-2 can remain infectious on surfaces for several days.
The stability of human coronaviruses on various types of surfaces depends on many factors, including viral titers, medium and substrate of viral inoculation, humidity, temperature, and ultraviolet exposure. Although the risk of surface transmission is considered to be low, there remains a possibility of SARS-CoV-2 transmission through contaminated drinking glass because of its direct contact with the mouth.
In the current study, scientists have determined the stability of human coronaviruses on glass surfaces. In addition, they assess the ability of common household detergents and glass cleaning processes to inactivate and eliminate viruses from glass surfaces.
The current study used alpha coronavirus HCoV-229E as a surrogate virus for SARS-CoV-2. Both viruses were inoculated on sterile glass slides and allowed to dry inside a biosafety cabinet. The infectious virus titers were determined at multiple time points at room temperature, in dark conditions, or in the presence of indirect sunlight.
To determine viral inactivation, the virus on the glass surface was exposed to three different detergents at room temperature and at 43°C. The temperature was selected based on the United States Food and Drug Administration (FDA) guidelines. Besides detergents, the ability of a manual glass scrubbing device to eliminate the virus from glass surfaces was also determined.
Viral stability on glass surfaces
Various experimental conditions were used to determine viral stability on glass surfaces. To this end, the infectious virus remained stable on glass surfaces for up to seven days under daylight conditions. After three days, a reduction in viral titer was observed; however, the presence of an infectious virus on glass surfaces could not be detected 14 days after inoculation.
In the dark condition, the infectious virus remained stable on glass surfaces for up to 21 days. However, a reduction in viral titers was observed at days three, 14, and 21 post-inoculation. On day 28 post-inoculation, no virus was detected on glass surfaces.
Virus inactivation by detergents
The virus was exposed to three different dishwashing detergents for 15 and 60 seconds at room temperature and at 43 °C.
The highest reduction in viral titers was observed when exposed to the tested detergents for 60 seconds at 43 °C. The detergents with a higher amount of surfactant caused a more rapid reduction in viral titers, even at a lower temperature and shorter exposure time.
Specifically, two out of the three detergents caused almost complete inactivation of the virus after an exposure of 15 seconds at room temperature. However, the third detergent required a 60-second exposure time at 43 °C to completely inactivate the virus.
Virus elimination by glass cleaning devices
Virus-contaminated drinking glasses were used to determine the ability of a manual glass scrubbing device to eliminate the virus. For washing, the water temperature was maintained at 18 °C or at room temperature.
At both temperatures, no infectious virus was detected on drinking glasses after completion of the washing procedure.
The current study reveals that human coronaviruses can remain stable on glass surfaces for several days. Moreover, a dark environmental condition is more favorable for viral survival than a daylight condition.
Importantly, the study findings highlight that common household dishwashing detergents and manual glass-cleaning devices are sufficient to inactivate and eliminate viruses from glass surfaces.
- Schilling-Loeffler, K., Falkenhagen, A., & Johne, R. (2022). Coronaviruses are stable on glass but are eliminated by manual dishwashing procedures. Food Microbiology. doi:10.1016/j.fm.2022.104036.