A new survey has found that one in five people having HIV in UK are not aware of having the virus.
Public Health England (PHE) said that of the 98,400 people having HIV, there are 21,900 who do not know about it.
These newly released numbers are for 2012, and have shown a slight decrease on the previous year, the Independent reported.
Professor Noel Gill, head of PHE's HIV department said that in the UK, people who are unaware of their infection, are most likely to be at risk of transmitting HIV to others.
He added that they must increase the speed at which they are reducing the number of undiagnosed HIV infections by encouraging earlier and more frequent HIV testing, especially by those most at-risk.
45 percent of new HIV cases were detected among heterosexuals, accounting for 2,880 cases and gay men remained the most affected.