Posted By Chris Packham Paul I have doubts about the efficacy of hand washing as a mean of preventing inhalation of the virus. (And having discussed this with several microbiologists, I don't think I am the only one.) Whilst I have no reservations about high standards of personal hygiene, I wonder how a virus on the hands will actually be inhaled? The standard nuisance dust mask or the simple cloth masks that you see in images on the TV are useless when it comes to preventing inhalation of airborne viruses. You need to go to a higher level of protection. However, even this may not be adequate. I have a copy of a presentation given at a CDC meeting in the USA that shows how the virus can spread. It suggests to me that even at greater distances than you mention the potential for inhalation is considerable. If you would like a copy of the presentation drop me an e-mail. Chris

Posted By Dave Merchant NHS/HPA guidance at this time (Doc 080772) is that FFP3 respirators are only required for staff performing tasks which will aerosolize the virus in quantity (intubation, suction, nebulisers). Staff within ~1m of a patient should wear a standard issue fluid-repellent surgical mask, as should patients if they are being moved through communal areas. The line taken by "media doctors" that masks are useless isn't true, but rather masks __used in the way the general public would wear them__ are of limited benefit, as they would be wearing them for extended periods, often re-using them and touching them with unwashed hands, etc. H1N1 is proven to be viable in aerosol droplets for over 24 hours, as it is on metal surfaces. Viability on porous materials, cloth etc., is far less, typically an hour or two at the most, and around 15 minutes for living skin. The issue with paper masks "getting wet" is that the virus is initially outside the mask in droplets of water vapour, which is gradually soaked into the paper as you inhale. The primary mechanism to filter particles of 100nm and below (H1N1 is about 100nm diameter) is diffusion, the efficiency of which drops as the matrix becomes wet. Eventually, some virus will reach the inner surface and evaporation during inhalation will carry it to the user. Fluid-repellent / FFP3 masks retain the moisture on the initial contact surface for much longer than DIY paper dust-masks, and some are impregnated with disinfectants. NHS staff are also trained in barrier protocols and know, for example, to wash their hands before adjusting the mask in case they contaminate the inner surface. The logic for some countries to issue paper masks is based on what I said above about survival times - if a location is bad enough to warrant a mask, you're hundreds of times more likely to pick up the virus from the door handle / desk / table / shopping trolley, but to be infected it must be inhaled or transferred to your mouth. A DIY paper mask may not stop you inhaling the aerosols, but it sure reminds you not to lick your fingers.

Posted By Paul Durkin Thanks all for your excellent responses. However,still concerned about care workers having sufficient training: when / how to wear masks.Also are we talking HEPA masks? Regarding sneeze distance, this could produce an aerosol up to 4m away ,at a speed of 100mph so the 1m distance seems a bit arbitrary. Regards,Paul