British athletes are being told not to shake hands in case they catch a bug which wrecks their Olympic dreams.
A mild bug which can knock athletes off their stride could be picked up in the "quite stressful environment" of the Games, according to Dr Ian McCurdie, the British Olympic Association (BOA) chief medical officer.
It could hamper an athletes' chances of performing at their best, he said.
On whether this means shaking hands should be off-limits, he said: "I think, within reason, yes.
"I think that is not such a bad thing to advise. The difficulty is when you have got some reception and you have got a line of about 20 people you have never met before who you have got to shake hands with.
"Within reason if you do and have to shake hands with people, so long as you understand that regular handwashing and/or also using hand foam can help reduce the risk - that would be a good point."
The advice is part of a detailed package of health and resilience issues which the BOA has looked at ahead of the Games.
Tips for the 550-strong team of athletes and 450 support staff who will work with them include regular handwashing and use of a special protective hand foam as an extra barrier.
The BOA has declared it intends to send a best-prepared team to London 2012. Everything from allergy screening through to warning athletes that any symptoms should be reported early has been noted.
Probiotic drinks, containing friendly bacteria to try to ward off infection, may be a preferred tipple for some athletes.
Dr McCurdie said: "Almost certainly, I believe, the greatest threat to performance is illness and possibly injury.
"At an Olympic Games or any major event the performance impact of becoming ill or even feeling a little bit ill can be significant.
"Essentially we are talking about minimising risk of illness and optimising resistence. Minimising exposure and getting bugs into the system and being more robust to manage those should that happen.
"Hand hygiene is it. It is all about hand hygiene."
He notes that the Olympic environment is "a pretty hostile one" and that it will be a first-time experience for many athletes and support staff.
Housing is dense, people will share rooms and eat with the 204 other nationalities who compete at the Games. Anything from cutlery through to door handles could have unwanted bugs lurking on it, the advice says.
The health of the whole team, including the support staff such as medics and coaches, is the BOA's priority.
It said they can expect sleep deprivation, long working hours and having to cope with living in a different place. If they are feeling unwell, there is also a danger they could make poor decisions.
Dr McCurdie said: "Anything we can do to try to reduce those stresses and improve that function will help the support staff to support the athletes.
"Being at home adds another layer of stress.
"Being at an Olympic Games means you are normally inside a bubble and so there is effectively quite a limited number of people that you interact with when you are away in another country.
"In London we do not believe that is going to be the case. The variety of people the athletes and support staff are going to interact with is going to be huge."