Cases of tuberculosis (TB) in England, Wales and Northern Ireland have risen by 11% in just one year, according to new figures.
The Health Protection Agency (HPA) said there were 8,113 cases in 2005 - up 10.8% on the 7,321 cases in 2004.
Levels of TB have been increasing year on year in the UK since the late 1980s, but this is the largest increase in any one year since 1999.
The highest proportion of cases were in people from an Indian, Pakistani and Bangladeshi ethnic background - up from 2,574 cases in 2004 to 3,075 cases in 2005.
Dr John Watson, head of the HPA's Respiratory Diseases Department, said the largest increase was seen among people not born in the UK, who accounted for 5,310 cases.
Levels of TB in the UK-born population remained stable, he said.
Only 22% of the non-UK born sufferers in 2005 arrived in the UK during the past two years, he said.
"This suggests that the increase is not a result of a large number of individuals arriving recently with TB but rather a combination of TB disease developing in individuals who may have been infected for some time and new infections acquired in the UK, or as a result of travel to other countries where TB is common," he said.
TB, which can kill, is treated with special types of antibiotics, which have to be taken for months at a time.
A Home Office spokesman said: "Last year the Government introduced the first phase of its overseas screening programme for TB for people applying to enter the UK for more than six months in four high-risk countries, in line with proposals made by the Government in its five-year strategy earlier this year.
