World TB Day 2022: Screening to stop the spread

Published: 24 March 2022

Tuberculosis (TB) is a bacterial infection, affecting the lungs that is spread through inhaling tiny droplets from the coughs or sneezes of an infected person. The diseases is responsible for more than a million deaths worldwide every year, with more than ten million cases occurring annually.

While the disease itself is both curable and preventable, it still has a devastating impact. This is why, every year, the World Health Organisation marks World TB Day, as a chance to raise awareness about the disease and step up efforts to reduce its prevalence.

Here at St George’s, we are leading on multiple studies to tackle the disease, including basic research to understand how the bacteria that causes the disease remains dormant in the body, clinical trials to improve treatment of the disease and population studies to understand if TB increases the risk of other diseases.

Another area of focus is limiting the spread of TB by understanding data on a population level, both nationally and internationally.

A new study, led by the Migrant Health Research Group at St George’s and published today, sheds light on current shortfalls in TB screening programmes for migrant groups in European countries and what might be needed to better control the disease in Europe and improve health outcomes in migrants.

Stopping latent TB from activating

The new paper explores screening for latent TB infection (LTBI), which is when a person is infected with the TB bacteria, but does not have any symptoms. LTBI can activate when the immune system is compromised, at which point the disease becomes transmissible. Screening is therefore needed to identify people at risk.

Recent estimates place the current global LTBI prevalence at 1.3 billion people (roughly one in four people worldwide).

With some countries having greater rates of LTBI than others, countries with a low incidence of infection often focus on screening new arrivals from countries with high rates of TB, in order to catch it early and reduce the chances of them becoming unwell.

Screening programmes need strengthening

The research team interviewed experts from 30 European countries about their screening programmes to find out more about what is being done across the continent when new arrivals reach the border.

They found that 15 countries had LTBI screening programmes targeting migrant groups, while five had plans to implement them in future and 10 had no programme at all.

The majority of the experts in countries with screening programmes reported screening of asylum seekers and/or refugees (12/15). Nine reported screening migrants who were undocumented, eight reported screening migrants who were students, and seven reported screening migrants who were labourers. Six experts reported screening all the above categories of migrants.

In terms of treatment approach, 10 of the 15 experts stated that their countries offered treatment to all migrants diagnosed with LTBI, but two reported that they only offer treatment to younger adults (under 40 years old and under 35 years old).

One issue found across countries was the high drop-out rate, given that treatment for latent TB infection involves multiple medications, which need to be taken over a six-month period. Eight experts reported that adherence to treatment was the biggest challenge, and six experts reported that migrant communities have a higher drop-out rate than non-migrants.

“You can set these programmes up, but unless you invest in supporting people throughout the screening and treatment process, then a lot of effort goes to waste,” says lead author Dr Sally Hargreaves, from the Institute for Infection and Immunity at St George’s.

“In another recent study, we found that in migrants presenting to health systems who had a positive test for latent TB, only 52% ultimately initiated and completed treatment,” she adds.  

“The delivery of these screening and treatment programmes will require further strengthening if the targets to eradicate tuberculosis in low-incidence countries are to be met, with greater focus needed on engaging migrants more effectively in the clinic and understanding the diverse and unique barriers and facilitators to migrants initiating and completing treatment.”

The crisis could be worsening

With increased migration across Europe, as well as the negative impact of the Covid-19 pandemic on TB programmes and access to healthcare more broadly, there is a risk that disease rates could increase on the continent, and indeed globally.

“Many more excess deaths are being predicted from TB in the coming years,” says Dr Hargreaves.

“Fewer people have been coming forward with symptoms, and don’t get picked up quickly enough… the impact of the Covid-19 pandemic on health systems and the control of diseases such as TB has yet to be fully realised.”

The later people present to a clinician, the greater the risk of long-term complications and death from this disease.

The theme of World TB Day 2022 is ‘Invest to End TB. Save Lives,’ the aim being to stress the urgent need to invest resources to ramp up the fight against TB, “which must include investing into a new effective, and affordable vaccine” added Dr Hargreaves.

With the Covid-19 pandemic putting the goal to end TB at risk, an increased investment in screening and treatment programmes could be one way to curb the disease’s rise and stop it in its tracks.