Fresh air! Ventilation! Open windows! That's what a professor resident in West Cork recommends to combat Covid-19.
We wash our hands, yes. We wear face coverings, yes. We practice social distancing, yes. But, says Professor Edward Lynch, who spoke to me from his home in Schull, we have seriously overlooked one of the most useful ways of halting the virus: fresh air.
He's shocked when he sees buses with seats taped off for distancing, but windows sealed up, thus facilitating the spread of the infection.
Confined spaces, says the prof, are one of the biggest transmitters of coronavirus. Masks certainly help prevent the virus's droplets from spreading, but without healthy ventilation in any room, space, or area, the airborne particles can still disseminate.
Professor Lynch, aged 63, is experienced in the study of medical hygiene and garlanded with many honours: he's been Professor of Dentistry at Warwick University and principal director of Biomedical and Clinical Research at Nevada in the US.
He's listed among the world's top doctors of 2020 in dentistry and still does some teaching at DeMontfort University in Leicester.
Medical dentistry is focused on the transmission of infections and viruses, because the mouth and facial area are pathways for respiratory infections and respiratory disease.
Practice and research have led him to the conclusion that fresh air and ventilation have been a seriously neglected aspect of the fight against coronavirus. Health guidelines should be "hands, face, space, air," he says.
"Unfortunately, international health organisations, like the World Health Organisation, continue to place insufficient emphasis on this. Ventilation helps remove exhaled, virus-laden air, lowering the overall concentration and therefore any subsequent dose inhaled by people in the space."
Open those windows: at home; in public transport; in private cars, if more than one person is travelling. Air-conditioning should not be used unless it is properly filtered. Air-conditioning which merely recycles air is a vector of viral transmission.
Yes, gyms should, indeed, be kept closed, he says. "People puffing and panting in an enclosed space - the worst thing."
But golf clubs should be kept open. Walking the length of a golf course is one of the healthiest things you could do. Churches should be allowed to open for services - if they are big enough to circulate fresh air.
Indoor pubs, alas, really are transmitters of the virus. A lot of folk mingling together in an enclosed space? Bad idea.
A pub would need "12 air changes an hour" to keep it safe. (Aside from the disinhibiting factor of alcohol.) But drinking out of doors, providing there aren't close encounters, should be fine. The pub of the future will have an annexe where al fresco imbibing can take place.
The professor, who is on the editorial board of medical and scientific journals, can cite scholarly research papers with evidence that ventilation and fresh air are effective defences against Covid transmission (for example, the studies published recently in the National Library of Medicine by Lidia Morawska et al, and Mahesh Jayaweera et al).
And yet this fresh air advocacy isn't new: one of the most ardent campaigners for the healing powers of fresh air was Florence Nightingale, who pioneered modern nursing in the Victorian era. Nightingale believed that bed-rest and fresh air were two of medicine's most effective paths of recovery and good health.
Before antibiotics were available, people suffering from respiratory diseases like TB were packed off to sanatoria, where they would be dosed with fresh air - their beds parked on balconies. Influential paediatricians, like Frederic Truby King, recommended putting children out in their prams in all weathers to inhale the oxygen of fresh air.
So, when did all this change? Probably with the advent of central heating (and air-conditioning). Central heating made homes cosy and double-glazing sealed in the warmth.
And that, very likely, has contributed to the spread of infection in care homes, which are so frequently over-heated, stuffy and under-ventilated.
"Safety" was another trend which changed habits: trains, for example, routinely had windows which passengers could open, accompanied by a notice saying it was dangerous to lean out of the window (in Continental Europe, in various languages). Then it was considered easier just to seal the windows altogether - again, making a hospitable space for the transmission of infections.
The basic guideline should be: "get the old air out, get the new air in". The prospect of a vaccine against Covid is heartening, says Professor Lynch, "but don't bank everything on a vaccine". There are a lot of ifs and buts. And Covid will be with us for some time yet, anyway - probably for the rest of our lives.
In the meantime, there is a cheap and easily available common-sense defence against its spread: ventilation.
Professor Lynch hails originally from Cootehill in Cavan and is married to a Frenchwoman, Helene. ("She comes from Provence, but prefers life in West Cork - and she's a fabulous cook.") Their home looks out on a stunning view of the Fastnet Rock, which must provide abundant sources of that health-giving and virus-defeating element - fresh air.