By Catherine Burns
Newsbeat reporter in Leicester
Officials are worried not enough women are having tests
Health officials in Leicester say at least 45 women have been in touch with them after an HIV scare.
A man in the city has realised he has the virus and is worried he could have passed it on to up to 100 girls he slept with after meeting them in nightclubs.
The man hasn't been named but health officials want the message to get out.
Between 2002 and 2007 he went out in Leicester every week, mostly to the Burlington Club or the now-shut After Dark.
He often had sex with girls he met and usually didn't use a condom.
Health officials say there's no reason to think he knew he had the virus, and now he's trying to help them alert women he could have infected.
Chloe Leggat is from the the Health Protection Agency (HPA) and says this kind of case is rare.
She said: "Because this guy's been so open, we've been able to put information out there to help women identify themselves."
She says in one week 45 women have phoned a special NHS Direct number for advice about this, 0845 6030897.
But she's hoping even more will have gone straight to their doctors or a clinic to get tested.
Health officials in Leicester say 45 women have been in touch
She said: "It's impossible to say exactly how many people have attended somewhere for a screen.
"So there may be a lot more people that have turned up for a test that we don't know about."
She says it's a concern that some people will need to be checked out, but aren't doing anything about it.
But, she points out, people don't often rush to take HIV tests, but take their time to think through all the implications.
"Just because we haven't had a flurry of people, we hope it's going to be more of a slow drip thing when the time's right for them," she added.
Like most cities, there are several places you can go to in Leicester to get an HIV/Aids test.
As well as specialist sexual health services, you could just make an appointment with your GP.
There's a walk-in centre at the Leicester Royal Infirmary. Doctor Paul Schober is a consultant there.
If they don't have a test it doesn't mean they don't have HIV, it just means they don't know about it
Chloe Leggat from the Health Protection Agency
He reckons he's seen around 15 people linked to this case.
He said: "They're very anxious. It's the fear of the unknown. Are they infected? If so, what does it hold for their future?"
He says because the risk dates back as far as 2002, some people are in new relationships now and are worried they could potentially have infected other partners too.
Both he and Chloe Legatt have the same advice for anyone who's worried.
They say unprotected sex is always a risk, especially with a new or casual partner. So if in doubt, get tested and put your mind at ease.
She said: "If they've got it, it's not going to go away.
"If they don't have a test it doesn't mean they don't have HIV, it just means they don't know about it.
"And they won't be able to get the help they need."