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Covid-19: Stale air helps transmit the coronavirus

A Cambridge doctor says he wants the government to do more to warn the public that infected air is a major source of transmission of Covid-19 and that ventilating rooms is just as important as washing hands.

He warned that the need to open windows and ventilate indoor spaces to disperse the virus is not being publicised enough by the government when research shows eight out of ten cases are caused by breathing in infected air.

And he says cloth masks offer only “minimal protection” against these tiny particles which can stay floating in the air.

Cambridge consultant physician Matt Butler warns that cloth masks offer "minimal protection" against airborne transmission of the virus.
Cambridge consultant physician Matt Butler warns that cloth masks offer "minimal protection" against airborne transmission of the virus.

This week he and more than 900 other health care professionals have written an open letter to the Prime Minister asking for better PPE and ventilation in hospitals to prevent the spread of Covid-19 through inhaled stale air.

Matt Butler, a consultant physician in Cambridge, said: "When you watch the news, Hands, Face, Space is what’s on the podium.

“I don’t think I have heard the Prime Minister once say people need to be mindful that when they are in an indoor setting they need to open windows to ventilate the room. The government does mention the importance of ventilating rooms on their website but there isn’t a focus on it in their messages to the public. As a doctor I feel that one of my duties is to communicate about public health and I think this is an important message.

"When you look at the government's websites they do tell people about airborne transmission and the need to ventilate rooms but they are not advertising it.

"Advice to the public needs to be Hands, Face, Space, Replace - as in replace the air in the room. The other important thing is time the less time you spend with someone the less likely you are to be infected.

"What we do know is that the virus can be transmitted in the air. We know that you can isolate live viruses from the air and we know that people have caught it from a single individual over two metres away. So it must be airborne.

“I’m concerned that everything we have been doing isn’t working to prevent people catching it. You can see that it’s very straightforward if you look at the numbers of cases rising. The current precautions are just not enough and if you have something that is out of control then you need to do something extra.

The cloth masks we are all advised to wear offer minimal control against aerosols coming out or being breathed in.

“These extra precautions about ventilation, from the evidence, would seem to be the next most logical step to take. These sorts of aerosols build up in a room over time and you can get infected from this stale air. I don’t think people are that aware about it."

At the start of the pandemic the general belief was that the virus was spread by droplets coughed or sneezed out by infected individuals or by touching a contaminated surface, which is why people are advised to wash their hands.

But in their open letter to the government, the medics state that a study has shown 80 per cent of infections are contracted by inhalation of the virus, rather than through droplets spread by coughs and sneezes or touching contaminated surfaces.

Dr Butler says: “The reason we have written this letter to the government is because dogma and infectious disease training and public health training ever since the 1930s is very much based on droplet spread of disease. But it’s very hard to protect against small particles (in the air).

“The cloth masks we are all advised to wear offer minimal control against aerosols coming out or being breathed in.”

His comments are backed up by a report from the government’s own scientific advisors, SAGE, which says: “The virus that causes Covid-19 is spread through very small aerosols and droplets released in exhaled breath. There is evidence to show that in some cases these aerosols can be carried more than 2m in the air and could cause infection if they are inhaled.

“This is most likely to happen in indoor environments when the ventilation in a room is poor. If people spend sufficiently longer periods of time in the room, the virus can build up in the air and people can inhale enough of it to cause infection.”

The letter to the government signed by Dr Butler explains that now this airborne transmission has been recognised, healthcare staff working with patients who have Covid-19 or are suspected of having the illness need a higher grade of mask to protect them from virus particles drifting in the air. At the moment these special masks are only used in intensive care.

Dr Butler told the Cambridge Independent that all staff working with Covid-19 infected patients needed better masks to protect them from catching the infection, not just those working in intensive care.

The letter says: “It is now essential that healthcare workers have their PPE upgraded to protect against airborne transmission.”

It adds in order to “take back control of the situation in our health care settings” they want “immediate access to FFP3 masks for all staff working with confirmed or suspected Covid-19 patients”, as well as a review of national PPE guidance.

They also ask the government to “ensure hospitals immediately increase natural ventilation as much as possible in all clinical settings where current standard requirements are not currently met.”

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