The East London and the City HA report is determined to 'explode some of the important myths about TB'.

It breaks down the factors linked to infection: poverty, overcrowding and homelessness, HIV and AIDS, immigration from high-TB areas, failure to control spread of the disease, close contact with sufferers or people with chronic poor health and drug and alcohol dependence.

Links with homelessness are clear: the report says at least 25 per cent of London's homeless are infected with TB, 2 to 3 per cent actually ill with the disease.

A connection between TB and immigration is less clear: 'Contrary to entrenched prejudice, our high local rates are not primarily explained by people 'bringing TB into the country', ' the report states. Less than a third of TB cases have occurred in those who have lived in east London for fewer than five years.

But there is a strong link with ethnic background: just 13 per cent of TB notifications in the HA area between 1995 and 1998 involved white people. Dr Jacobson says this is related to wider issues such as poverty and over-crowding.

It is a sensitive area: not least, points out Dr Citron, because of the cultural significance of TB: 'In many countries if a woman is known to have TB she becomes unmarriageable, because it is well-known as a disease of the 'bottom part of humanity' - or poverty as we might call it.'