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In the UK, migrants and ethnic minorities have higher rates of tuberculosis (TB) compared with the general population. Much of the focus has been on pathogen exposure to explain the disparity. However, in their review published in F1000Research, Sally Hayward and Rachel Tanner explain that there are multiple factors at play. Here they discuss how these factors could contribute to the different rates of TB between groups and populations.

The stats

According to the most recent Public Health England data, in 2016 nearly three-quarters of those diagnosed with TB disease in the UK were foreign-born, with India and Pakistan the most frequent countries of birth among such cases. While TB rates have been falling slowly across all UK populations since 2011, they remain 15 times higher in the foreign-born than the UK-born population.

Stigma and assumptions

The media have often claimed that migrants and ethnic minorities ‘import’ TB to the UK. For example, according to The Daily Express following a TB outbreak in Leicester in 2001, “we are still vulnerable to infection from other countries” because “immigrants and visitors from less medically advanced countries can carry the infection into Britain”. In this way, migrants and ethnic minorities are stigmatised and labelled as carriers of infectious disease.

This popular view attributes the disparity in TB rates solely to higher exposure among migrants and ethnic minorities to TB bacteria in high-incidence countries. Although this undoubtedly plays an important role, assuming that it is the only driver fails to address the complex interplay of factors influencing the vulnerability of particular migrant and ethnic groups to infection and progression from latent infection to active disease.

The key factors

There are various biomedical factors that increase the vulnerability of migrants and ethnic minorities to TB. The only available TB vaccine, BCG, doesn’t provide protection in many migrant countries of origin such as India. While contested, there is evidence to suggest that genetic ancestry plays a role in greater TB susceptibility, particularly in African populations.

Among Asian populations, it is thought that vitamin D deficiency contributes to increased susceptibility. Certain migrant and ethnic groups are also at higher risk of various conditions that impair immunity and therefore increase risk of progression to active TB disease, such as diabetes mellitus, HIV and chronic kidney disease.

Against this biological backdrop, a fundamental driver behind the observed disparity is the association between TB and poverty. Migrants and ethnic minorities in the UK are more likely to be socio-economically disadvantaged, and there is a recognised role for poverty, homelessness and overcrowding in the spread of TB infection and the number of active cases.

In addition, the difficulties and stresses faced during and shortly after migration can increase risk of progression to active TB disease. Certain migrant and ethnic groups face barriers to accessing treatment including cultural differences in treatment-seeking behaviours, stigmatisation of sufferers, and barriers to healthcare access. The resultant delays in diagnosis and treatment lead to increased transmission and incidence in these communities.

Improving the situation

Currently, migrants from countries with high TB incidences are screened for active TB before entry to the UK. However, such measures only address the driver of differential exposure to the TB bacteria. More consideration must be given to policies concerned with the vulnerability of migrants to reactivation of latent TB infection following arrival in the UK. This might include vitamin D supplementation, managing co-morbidities, and the promotion of socio-economic equity and migrant rights.

To reduce delays in diagnosis and treatment, and thereby minimise transmission within migrant and ethnic minority communities, increased health education on TB causation, risk and transmission is required, as well as tackling stigmatisation of vulnerable groups.

It is also important to raise awareness of migrants’ entitlement to diagnosis and treatment through the NHS, alongside reducing cultural, economic and political barriers to its access.

Enhancing TB research

We chose to publish in F1000Research for several reasons, one of which was to contribute to the World TB Day Collection which brought together a range of primary data papers, opinion pieces, methodology and other content with the aim of enhancing and enriching TB research.

Importantly, F1000Research allowed us to explore social and biological factors in a single review article, unconstrained by the disciplinary boundaries often characteristic of more specialist journals.

We were also attracted by the very short timeline to publication, and the fact that papers are fully open access which ensures broad availability and maximises impact. The open peer review process was a first for us, but it seems like a revolutionary model that makes the process more transparent and encourages more thorough, constructive and fair feedback. It also enables reviewers to receive recognition for their hard work.