If you can smell someone else's perfume or aftershave, you're too close to them. If you're near someone and they are speaking loudly because the music is loud, or even if there's no music (how we Irish love to shout after a few drinks), you're in danger of becoming infected. If someone puts their arm around you, calling you their best friend, there's a chance you'll become infected.
Of all the features of the Covid-19 virus, who would have thought an Irish pub would be the optimum environment for it to spread in?
The whole reason you go to a pub is to have someone smell your aftershave (or pheromones), shout a terribly interesting story, and lose your inhibitions.
It's our God-given right as Irish people to be able to do this. It's like Mother Nature is playing a joke on us Irish. And whatever you do, don't laugh uproariously. This virus likes nothing better than a good laugh to spread. Except now the laugh is on us. The smoking ban didn't do for the Irish pub, but the virus did.
Study after study has confirmed that bars and nightclubs are among the most dangerous places when it comes to catching Covid-19. The Texas Medical Association, as well as the combined analysis of the New York Times, Reuters and National Public Radio, all place bars at the top of the list of risky activities.
On June 8, a pub reopened in Michigan after weeks of being shut. Safe practices were adopted, including cleaning regimens, pushing tables six feet apart, and limiting the number of customers. By July 2, 152 infections had been tied to the bar.
A local doctor said: "I think taking precautions is important. But at the end of the day, no matter how many precautions you take, some things are just high-risk, and bars are one of those things."
In Zurich, a man who had visited the Flamingo Club tested positive. Five other customers tested positive, and all 300 who were there were placed into quarantine last Saturday. Swiss authorities have said that if a similar event occurs in a pub or club, all such venues in Zurich will be shut down.
To make matters worse, the World Health Organisation (WHO) is likely to conclude that the virus can be spread by tiny particles suspended in the air that are breathed out and can travel beyond two metres.
This will further emphasise how a crowded, poorly ventilated indoor space is a high risk - a risk that can only be effectively mitigated against with strong ventilation (one recommendation states that it should be almost uncomfortable), use of masks in such settings, and more rigorous distancing.
Kimberley Prather, an atmospheric chemist in San Diego, has said that if you are in a room with a super-spreader, you will breathe their air at some point, with as many as 80pc of people in the vicinity becoming infected.
The virus has been shown to traverse the length of a room and remain viable in the air for perhaps three hours. In a crowded indoor space, a single infected person might therefore release enough aerosolised virus over time to infect many people.
If the WHO changes its recommendation, this will also have consequences for the reopening of schools, as many are likely to be poorly ventilated and are too poorly funded to invest in new filtration systems.
One somewhat positive aspect is that crowds outdoors may not pose that big a risk. Thousands of people flocked to beaches in Bournemouth in June, with the police having to intervene, but there is no evidence that this gave rise to a spike in infections.
But back to the pubs. We move towards July 20, the planned reopening date, although many have already reopened if they sell food (with a bag of peanuts not counting, as Tony Holohan, who knows the Irish well, has pointed out).
The food/drink combination will not apply to pubs reopening on July 20 though, losing the chance for food to provide that well known trick of seasoned drinkers: soakage. This must have been the intention for the first phase of reopening, as those on soft drinks were exempt. Surely a tacit admission that drunkenness might give rise to reckless behaviour.
Given the clear and present danger of pubs, what are the rules? These can be found in a Bord Failte 22-page document. Let's hope the publicans didn't think: 'Too Long, Didn't Read'.
Table service only; no queueing at the bar or socialising away from your table. One and a half hours maximum for each group. One person in each pre-booked group has to give their contact details, and note down each person in their group (who should be close friends or family members only). If there is adequate signage, floor markings and regular announcements on the rules, a table may be one metre from another table which has strangers. If not, it has to be two metres distant. You must wear a mask when you go to the toilet, but you can take it off at your table to allow you to keep drinking. Minimise things like umbrellas in cocktails. Straws must be individually wrapped. The cleaning requirements take up several pages of the guidelines. The safety instructions for the Apollo mission to the moon were probably less detailed.
If we want pubs to reopen, we have to make sure they follow these strict guidelines, which will have to be enforced by gardai. Good luck with that. Last weekend, 26 pubs were in breach of the rules, mainly concerning the serving of food. Not a great start. How powerful ventilation will be ensured in pubs is not at all clear, and who wants to sip their beer in a gale?
One fact, however, cannot be denied. Alcohol and social distancing are mutually exclusive. We drink alcohol to relax and that inevitably means we become less risk-averse, at the worst possible time.
What all of this means in practise is, pubs will still be places where you might become infected by breathing in the air of a super-spreader. You will have to assume that you will become infected. You will probably be all right, although some will be sick for a while and might have symptoms that linger for months.
More seriously, you might infect someone who is more vulnerable than you with deadly consequences. You might well be part of a chain of events that results in another lockdown.
We are seeing outbreaks in several countries. In Australia, parts of Melbourne have been shut down and they are halving the number of people being allowed to return home from overseas. Hong Kong is shutting all the schools again. On Thursday, we saw an increase in cases here, mainly in people under 44, with a warning that we must keep adhering to the public health guidelines, otherwise schools won't reopen. And what are we about to do? Reopen places that have the highest risk for the virus to spread again.
This means having pubs open must mean we abide by all the guidelines even more zealously, including the wearing of masks. Do you think we can do that? One look at Dublin city centre last weekend, and many anecdotal stories from pubs around the country, says not really.
Is it not best to just sit this round out, until the virus is under control? Otherwise pubs will trigger spikes of infection. Schools and businesses will have to close, with yet more economic damage and psychological stress.
If we open the pubs, we must close the airports, because that is where new infections will come from and will be spread in pubs.
We are opening the pubs at our peril. Think of them as meat-packing factories.
We should drink at home with friends. Unless we all behave ourselves on a night out. When it comes to us Irish and alcohol, we're great at that now, aren't we?
Luke O'Neill is professor of biochemistry in the School of Biochemistry and Immunology at Trinity College Dublin.