Human Coronavirus 229E Remains Infectious on Common Touch Surface Materials

Warnes, Sarah L.; Little, Zoë R.; Keevil, C. William

Viruses causing respiratory infections are spread by droplets expelled by coughs and sneezes, which can also contaminate the environment 2 m and 6 m away, respectively (33) , and a single droplet may easily contain an infectious dose (34) . Enveloped respiratory viruses, although more susceptible to environmental stress than nonenveloped viruses, have been shown to persist on surfaces and contaminate more than 50% of surfaces in household and day care centers (35) . Animal coronaviruses, including transmissible gastroenteritis virus (TGEV) and mouse hepatitis virus (MHV), have been shown to retain infectivity for long periods on hard surfaces (36) and for several hours on health care gowns, gloves, and masks (37), but human coronavirus 229E (HuCoV-229E) did not persist for above a few hours on surfaces (38) . In contrast, we have observed that a relatively low titer of infectious human coronavirus 229E persisted on 5 surface materials, common to communal and domestic environments, for at least 5 days. Our virus preparation contained a high proportion of lung cell debris to mimic natural contamination in respiratory secretions, which may have protected the virus from desiccation, and a human lung cell line was used for the assay, which may have been more sensitive. The relatively low virus concentration used suggests that higher viral concentrations which can occur in sputum may persist for longer periods. During coronavirus infection, the FIG 3 Comparison between brasses and copper nickels (containing the same percentage of copper) used to inactivate human coronavirus to determine if zinc content enhances the antiviral effect. Approximately 10 3 PFU was inoculated onto alloys containing 90% copper for 0, 5, and 20 min (A) or 70% copper for 0, 30, and 60 min (B) and was then removed and assessed for infectivity as described in the text. Alloys containing 90% copper were very effective at inactivating human coronavirus (A), but variations in efficacy did not appear to be related only to the presence of zinc. The presence of copper nickel C70600 resulted in increased efficacy compared to that of copper nickel C72500; that result may be linked to surface oxide layer or copper ion release from this alloy. However, at a lower percentage of copper (B), synergy with zinc or Cu(I) release may be important because contact with cartridge brass resulted in virus inactivation that was at least 3 times faster than that seen with copper nickel C71500. viral load is highest later in the infection and large numbers of infectious virus which may also contaminate the surrounding environment can be shed as symptoms subside over long periods (4) . There is scant information on minimum infectious doses, but for many respiratory viruses, the minimum infectious dose is believed to be low, i.e., just a few virus particles. Coronavirus persistence on surfaces represents a considerable infection risk if contaminated surfaces are touched and infectious virus transferred to the mouth, nasal mucosa, or conjunctiva. Nicas and Best (39) observed that individuals in office environments touched their face an average of 15 times an hour, giving ample opportunities for infection spread. The use of antiviral surfaces in health care and community facilities could help to reduce infection spread in this way. HuCoV-229E was rapidly inactivated on copper surfaces, with the inactivation rate being roughly proportional to the percentage of copper in the alloy. Alloys containing