When a tuberculosis notification lands on the desk of Surinder Bakhshi, the first thing the doctor wants to know is the patient's race.

"When I get a lab report through on a TB case, I first check which ethnic community it has occurred in. If it is in a community where I would not expect it, that worries me," says Bakhshi, a consultant in communicable disease control.

For while TB can infect any race, it is one of several illnesses, including coronary heart disease and sickle cell anaemia, that show dramatic variations in incidence depending on ethnic group.

In Birmingham in 1999 people of Afro-Caribbean origin were five times more likely to suffer from TB than the indigenous white population. The rate was 20 times greater among people of Indian descent and 26 times higher among people of Pakistani origin.

Leicester - one of the most ethnically diverse cities in the UK - had a TB rate that was four times the national average even before the current outbreak at Crown Hills Community College; last week numbers linked to this outbreak climbed to 50. The rate of coronary heart disease in Bradford among people of Bangladeshi origin is 30% above the national average for women, and 75% higher for men.

Discussion about the reasons for these variations can be difficult. It seems that just as party leaders Tony Blair, William Hague and Charles Kennedy have agreed not to play the "race card" in the coming general election, so some healthcare professionals are cautious of spelling out how someone's ethnicity can affect personal health.

Yet healthcare planners do take these factors into account in devising services. Earlier this year Leicester Royal Infirmary announced that it would build a £1.8m infectious diseases wing. It will take cases of TB, drug-resistant diseases and tropical fevers such as malaria.

Malaria is not contagious but it can be confused with fevers that are, and it is being seen more frequently in Leicester's health centres. The reason is straightforward: many of the city's residents visit malarious areas and have visitors from these regions.

The factors behind TB are more complex and disputed. It is a disease that can lie latent in someone's body for their entire life and develops to an infectious stage only in a minority of cases. What causes this transition has been described as the "holy grail" of TB research by Mike Barer, professor of clinical epidemiology at Leicester University.

At the turn of the 19th century, TB was rife in London and New York, but vaccination and effective treatment appears to have led to its decline in the first 40 years of the 20th century. However, since 1987 its incidence has risen by 34%. The public health laboratory service attributes this increase in part to immigrants moving to Britain from countries that have a high prevalence of the disease. But making a link between immigration and disease can be contentious.

Elizabeth Anionwu, head of the Mary Seacole centre for nursing practice at Thames Valley University, says: "Like many people, I get very hot under the collar when people start talking about ethnic groups 'bringing disease' into this country.

"It is not because of their background that certain groups of the population are [sicker]. It's because of language issues, institutional racism within the health service or a lack of awareness of services."

East London and the City health authority has the highest incidence of TB in the country and almost half the people in its area are from ethnic minorities. Its view is that its high TB rates are not primarily explained by immigrants bringing the disease into the UK.

A study by the authority found that less than a third of TB cases in east London occurred among people who had lived locally for less than five years and it concluded that poverty, homelessness and deprivation were major factors in both established and new communities in its area. The authority believes that these factors could weaken someone's immune system, causing them to develop the disease if they were already infected, or encourage its transmission.

John Nicholson, chief executive of the UK Public Health Association, says: "Certainly in this country the proportion of people from ethnic minorities in a community is closely correlated with socio-economic factors such as poor housing which will affect illnesses ranging from TB to coronary heart disease."

Daisy Choudhury, a community development officer who works for the Bangladeshi welfare association in Burnley and has witnessed the link between unemployment, low income and health, says: "Bangladeshis used to work in the mills and factories in Burnley. When these closed down, most of the men became unemployed. Slowly people's health got worse with coronary heart disease, cancer, kidney failure, high blood pressure and diabetes."

She started an allotment club for Bangladeshis so that they could have access to affordable, fresh vegetables and get exercise. The club is women-only because of cultural objections to men and women working together if they are not related.

Choudhury adds: "I did this for Bangladeshi women. The men still go shopping and go into town, but the women don't go out for a walk. They don't go out for anything. It's good for them to have the exercise."

But Bakhshi disagrees that deprivation is a factor among ethnic minority communities in the case of TB. He says research that he and colleagues conducted disentangled the effects of poverty and ethnicity on TB rates and found that it did not have a significant bearing on the incidence of the disease in Asian groups.

He says: "Some people are very wary of talking about the particular health needs of different ethnic communities. If we are wary, how will we overcome the disease?

"I am Asian. I am Indian. I'm not afraid to talk about it. I want Asian people to understand that if they have a cough that has lasted a couple of weeks, it could be far more significant than if a white person has a cough. It could be TB and they might be giving it to their grandchildren.

"TB is always going to be higher among people who have come from countries where it is prevalent and we must take steps to contain it. There is no shame and no embarrassment about it. TB is easy to manage and easy to treat, but if we are so sensitive about it that we don't talk about it, then that is immoral."