“Are you clean?” “Disease free and expect the same!” All phrases that have become depressingly familiar to many on the gay scene, and especially in the world of online hook-ups. And phrases that it’s worth taking a good hard look at, on World AIDS Day.

The numbers that I’m going to talk about here are for the UK; that’s where I am, and they’re very different elsewhere – we must not forget that, no matter how grim things may seem, as HIV/AIDS cuts a swathe through the gay community, that in some parts of Africa infection percentage rates are in the high 20s, over three times that of even the worst hit communities in the UK, and with far worse access to drugs.

But I digress. Something that is important to get across is the futility of those questions – not to mention their implicit assumption that, somehow, those with HIV are “dirty.” You might perhaps think that asking about someone’s status is a sensible thing to do – one young man I met a few years back seemed surprised that I told him it was none of his business, and pretty rude to ask.

I applaud and admire those who are open about their status; it can be hard to do when even a community that you think might be understanding is full of people who will run away or say “Oh, I could never get into a relationship with someone who’s positive.” Over the years, I’ve had a number of people say “before we play, you should know I’m positive,” and my reaction’s always been the same: “Thanks for telling me, but I wasn’t planning on doing anything unsafe.”

Those who say “a positive person must always disclose” seem to be following a slightly illogical process; if you’re going to change the way that you play, because someone tells you they’re positive, doesn’t that suggest that if they say they’re negative, you’ll be doing different things, some of which may be riskier?

And that’s where this becomes a question of numbers. One of the statistics that’s featured heavily in the news reports in the UK this year is that a quarter of those people with HIV don’t know that they are carrying the virus (in fact, I believe this is down from as many as a third a few years back, which is good news, of a sort). But it means that when you ask someone one of those horrible questions, if you take their answer at face value, you may be making a grave mistake.

In the UK gay community, the numbers for this year’s World AIDS Day tell us, around one in twenty people are carrying the virus. If a quarter of those don’t know, that means one in eighty.

Now, you may feel that’s a pretty small chance – and I guess it depends just how many gentlemen you entertain. But that’s a 1.25% chance in a random encounter that someone might be HIV positive and not know about it.

Move to London – the centre of the gay scene for many, with plenty of bars, saunas and a few backrooms, where there’s also quite a bit of unprotected sex, and things are rather worse, with as many as one in 12 men who have sex with men being positive. With a quarter of those not knowing their status that’s almost a one in fifty chance, or around 2%.

And what if you don’t know your own status, either? It takes two to tango, and if you’ve not been tested, you could be part of that two percent; in other words, in any random hook-up between two gay men in London, there’s a 4% chance – that’s one in 25 – that one of them will be positive and not know it.

What’s the message here? The first is, as they said in the original AIDS campaign back in the 1980s, “Don’t die of ignorance.” Get yourself tested – you can have a result in 15 minutes from a tiny prick of the thumb.

And the second is that it’s probably not worth asking questions when there’s a fairly good chance the answer could be meaningless. It’s up to everyone to understand risks, and make their own choices about how safe they want to be. Don’t rely on someone else making that calculation for you – their numbers might not add up.