Poverty, overcrowding, poor housing conditions… All these things, we learnt from a London Assembly report published last week, are contributing to an increase in the incidence of tuberculosis in the city.

The fact this most Victorian of diseases is on the rise is not exactly new information, either. In 2005, the BBC reported that the capital had 20 times the TB rate of the rest of the UK, and in 2010, the Telegraph described the city as “the TB capital of Europe”.

But how bad can it really be? The Tackling TB in London report is fairly explicit:

There were over 2,500 new cases of TB in London in 2014, making up approximately 40 per cent of all cases in the UK. One third of London’s boroughs exceed the World Health Organisation “high incidence” threshold of 40 cases per 100,000 population. And some boroughs have incidence levels as high as 113 per 100,000 people – significantly higher than countries such as Rwanda, Algeria, Iraq and Guatemala.

Ah.

Tuberculosis is caused by the mycobacterium tuberculosis bacteria, and mostly affects the lungs. The symptoms include persistent coughing, fever and tiredness. It’s spread by coughing and sneezing, but don’t start getting righteous on tube snifflers – you’d need to be in prolonged contact with an infected person to contract the disease.

It’s not incurable, but patients can need to take antibiotics for up to six months – more if the strain of TB turns out to be one that’s resistant to drugs. The other danger is from latent TB – where a person is a carrier but doesn’t actually have the symptoms.

TB had already been eradicated in the UK – but the disease has made a slow and steady return, thriving on overcrowding in deprived boroughs, poverty and Dickensian housing conditions. As Dr Onkar Sahota, chair of the Greater London Authority’s health committee, explains:

“The causes are complex and far from simply medical. TB affects those who most need our help: migrants, the elderly, prisoners, homeless people and those who are marginalised from society. TB has a relationship with deprivation as well as clinical causes.

“We know TB disproportionately affects prisoners, homeless people and people with substance abuse issues, and high quality TB care services are not universally available to all Londoners.”

As to where the disease is on the increase, some boroughs are beset by far more cases than others. Here’s a chart showing the 10 boroughs with the highest rates of infection:

Given the unfailing reliability with which some sections of the media crowbar the words “migration” and “ticking time-bomb” into their tuberculosis stories, it’s no surprise that a lot of people think migrants are bringing the disease to the UK. But the World Health Organisation (WHO) refutes this, stating that there’s “no systematic association” between migration and infectious diseases, adding that “communicable diseases are associated primarily with poverty”.

The writer of the report alluded to by the Telegraph, Professor Alimuddin Zumla of University College London, has made the same point. He noted that, while the increase in TB cases has been mainly among people born outside the UK, they appear to have been infected here rather than in their country of origin. With many migrants to London living in poverty, sleeping rough or in poor quality, overcrowded homes, it’s hardly a surprise that they are more at risk.

Crucially, WHO advise against limiting access to medical assistance for immigrants, legal or otherwise. Suddenly, charging migrants to use the NHS doesn’t seem like quite such a clever idea.

The homeless, another high risk group, are finding help in Hackney. The council has partnered with Homerton University Hospital to reduce what was once the highest rate of TB infection in London. Any homeless person with TB is given accommodation for the duration of their treatment, even if they’re not actually eligible for housing in the first place.

The result? The borough’s infection rate has dropped, and in July this year, the Homerton Hospital team won an award for their work.

In Newham, the borough with the current highest rate of infection (and, not coincidentally, one of London’s most deprived), the council has partnered with the NHS Newham Clinical Commissioning Group to screen for latent TB when residents register with a GP. Newham was also one of the first councils to introduce a crackdown on “slum” landlords to try and tackle overcrowding.

The London Assembly’s recommendations include a city-wide education programme, extending Hackney’s housing plan to other boroughs and universal provision of the BCG vaccination. With around 1m people living in poverty, and with housing conditions as poor as they are, Londoners’ health is also falling through the inequality gap.

You can read the report here (PDF).

Beth Parnell-Hopkinson is a senior editor at Londonist.