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12 WHO Infection prevention and control during health care when novel coronavirus (nCoV) infection is suspected.

13 WHO. Annex G Use of disinfectants: alcohol and bleach. Infection prevention and control of epidemic-and pandemic-prone acute respiratory infections in health care.

13 WHO. Annex G Use of disinfectants: alcohol and bleach. Infection prevention and control of epidemic-and pandemic-prone acute respiratory infections in health care.

Human coronaviruses can remain infectious on inanimate surfaces at room temperature for up to 9 days. At a temperature of 30°C or more the duration of persistence is shorter. Veterinary coronaviruses have been shown to persist even longer for 28 d. Contamination of frequent touch surfaces in healthcare settings are therefore a potential source of viral transmission. Data on the transmissibility of coronaviruses from contaminated surfaces to hands were not found. However, it could be shown with influenza A virus that a contact of 5 s can transfer 31.6% of the viral load to the hands []. The transfer efficiency was lower (1.5%) with parainfluenza virus 3 and a 5 s contact between the surface and the hands []. In an observational study, it was described that students touch their face with their own hands on average 23 times per h, with contact mostly to the skin (56%), followed by mouth (36%), nose (31%) and eyes (31%) []. Although the viral load of coronaviruses on inanimate surfaces is not known during an outbreak situation it seem plausible to reduce the viral load on surfaces by disinfection, especially of frequently touched surfaces in the immediate patient surrounding where the highest viral load can be expected. The WHO recommends “to ensure that environmental cleaning and disinfection procedures are followed consistently and correctly. Thoroughly cleaning environmental surfaces with water and detergent and applying commonly used hospital-level disinfectants (such as sodium hypochlorite) are effective and sufficient procedures.” [] The typical use of bleach is at a dilution of 1:100 of 5% sodium hypochlorite resulting in a final concentration of 0.05% []. Our summarized data with coronaviruses suggest that a concentration of 0.1% is effective in 1 min ( Table III ). That is why it seems appropriate to recommend a dilution 1:50 of standard bleach in the coronavirus setting. For the disinfection of small surfaces ethanol (62–71%; carrier tests) revealed a similar efficacy against coronavirus. A concentration of 70% ethanol is also recommended by the WHO for disinfecting small surfaces [].