Relating annual migration from high tuberculosis burden country of origin to changes in foreign-born tuberculosis notification rates in low-medium incidence European countries

Effects of migration on tuberculosis epidemiological indicators in low and medium tuberculosis incidence countries: A systematic review

BACKGROUND

Tuberculosis (TB) remains one of the top ten causes of death each year globally. While the risk of migrant TB is linked to the TB incidence in their country of origin, the migration process can increase the TB risk.

OBJECTIVE

We aimed to synthesis the evidence on key differences in the epidemiological profile of TB between migrants from high TB incidence birth countries and non-migrants resident in low to medium incidence TB countries.

METHODS

We conducted a systematic review where the population was all active TB cases in countries with low to medium TB incidence (<40/100,000 population), the exposure was migration to a low or medium TB incidence country and the comparator was non-migrant TB cases in low or medium incidence countries. Overall proportions were compared between migrants and non-migrants, using Fisher's exact test. Meta-analysis of proportions was carried out for the primary outcome (active TB) while meta-analyses of odds ratios (ORs) were performed using a random effects model for secondary outcomes; sputum-smear positivity, any first line drug resistance, multi-drug resistance (MDR), clustered cases, HIV coinfections and successful treatment. Heterogeneity was evaluated and sources were investigated using subgroup and sensitivity analysis.

RESULTS

Significant differences were found in the overall proportions of high TB incidence migrants and non-migrants for MDR cases, clustered cases, HIV coinfections and successful treatment, as well as a significant difference in the OR among MDR cases (3.91).

CONCLUSION

This review has demonstrated significant differences in key epidemiological indicators between high TB incidence migrants and non-migrants, indicating policy implications.

A population-based genomic epidemiological study of the source of tuberculosis infections in an emerging city: Shenzhen, China

Background

Tuberculosis (TB) in emerging cities is often a disease of recent immigrants, and understanding this epidemiology is crucial for designing effective control and prevention strategies.

Methods

We conducted a retrospective population-based genomic epidemiological study of culture-positive pulmonary TB patients diagnosed between June 2014 and November 2017 in the Bao'an District of Shenzhen, a Chinese city with dramatic recent growth. After whole genome sequencing, transmission clusters were defined as strains differing by no more than 12 SNPs.

Findings

Of 1696 culture-positive TB patients, 93•8% (1591/1696) were migrants, with 51•6% (821/1591) employed in housekeeping or unemployed. Of the 1460 migrants with known residence time, 47•7% (697/1460) developed TB within two years after arriving in Bao'an. Only 12•2% (207/1696) of Bao'an isolates were in genomic clusters, indicating that recent transmission was not the primary cause of TB in Bao'an. The isolates’ median terminal branch length was 56 SNPs, more than could have accumulated since the arrival of the migrants in Bao'an. The migrants’ isolates had genotypic distributions similar to those in their home provinces. One strain isolated in Bao'an belonged to a clade circulating in the patient's home province, providing further evidence that the strains were brought to Bao'an with the migrants.

Interpretation

TB in the Bao'an District is principally caused by reactivation of infections acquired by migrants in their home provinces. Nearly half developed TB within two years after arriving in Bao'an, suggesting a need for increased TB screening of migrants, especially housekeeping workers and the unemployed.

Funding

Sanming Project of Medicine in Shenzhen; National Science and Technology Major Project of China; Natural Science Foundation of China.

HIV diagnoses in migrant populations in Australia-A changing epidemiology

Introduction

We conducted a detailed analysis of trends in new HIV diagnoses in Australia by country of birth, to understand any changes in epidemiology, relationship to migration patterns and implications for public health programs.

Methods

Poisson regression analyses were performed, comparing the age-standardised HIV diagnosis rates per 100,000 estimated resident population between 2006–2010 and 2011–2015 by region of birth, with stratification by exposure (male-to-male sex, heterosexual sex–males and females). Correlation between the number of permanent and long-term arrivals was also explored using linear regression models.

Results

Between 2006 and 2015, there were 6,741 new HIV diagnoses attributed to male-to-male sex and 2,093 attributed to heterosexual sex, with the proportion of diagnoses attributed to male-to-male sex who were Australian-born decreasing from 72.5% to 66.5%. Compared with 2006–2010, the average annual HIV diagnosis rate per 100,000 in 2011–15 attributed to male-to-male sex was significantly higher in men born in South-East Asia (summary rate ratio (SRR) = 1.37, p = 0.001), North-East Asia (SRR = 2.18, p<0.001) and the Americas (SRR = 1.37, p = 0.025), but significantly lower as a result of heterosexual sex in men born in South-East Asia (SRR = 0.49, p = 0.002), Southern and Central Asia (SRR = 0.50, p = 0.014) and Sub-Saharan Africa (SRR = 0.39, p<0.001) and women born in South-East Asia (SRR = 0.61, p = 0.002) and Sub-Saharan Africa (SRR = 0.61, p<0.001). Positive associations were observed between the number of permanent and long-term arrivals and HIV diagnoses particularly in relation to diagnoses associated with male-to-male sex in men from North Africa and the Middle East, North Asia, Southern and Central Asia and the Americas.

Conclusion

The epidemiology of HIV in Australia is changing, with an increase in HIV diagnosis rates attributed to male-to-male sex amongst men born in Asia and the Americas. Tailored strategies must be developed to increase access to, and uptake of, prevention, testing and treatment in this group.

Reduction in tuberculosis incidence in the UK from 2011 to 2015: a population-based study

BACKGROUND

Following nearly two decades of increasing tuberculosis in the UK, TB incidence decreased by 32% from 2011 to 2015. Explaining this reduction is crucial to informing ongoing TB control efforts.

METHODS

We stratified TB cases notified in the UK and TB cases averted in the UK through pre-entry screening (PES) between 2011 and 2015 by country of birth and time since arrival. We used population estimates and migration data to establish denominators, and calculated incidence rate ratios (IRRs) between 2011 and 2015. We calculated the contribution of changing migrant population sizes, PES and changes in TB rates to the reduction in TB notifications.

RESULTS

TB IRRs fell in all non-EU migrant and UK-born populations between 2011 and 2015 (0.61; 95%  CI 0.59 to 0.64 and 0.78; 0.73 to 0.83 respectively), with the greatest decrease in recent non-EU migrants (0.54; 0.48 to 0.61). 61.9% of the reduction in TB notifications was attributable to decreases in TB rates, 33.4% to a fall in the number of recent/mid-term non-EU migrants and 11.4% to PES. A small increase in notifications in EU-born migrants offset the reduction by 6.6%.

CONCLUSIONS

Large decreases in TB rates in almost all populations accounted for the majority of the reduction in TB notifications, providing evidence of the impact of recent interventions to improve UK TB control. The particularly large decrease in TB rates in recent non-EU migrants provides evidence of the effectiveness of screening interventions that target this population. These findings will inform ongoing improvements to TB control.

Molecular epidemiology of tuberculosis in Tasmania and genomic characterisation of its first known multi-drug resistant case

Background

The origin and spread of tuberculosis (TB) in Tasmania and the types of strains of Mycobacterium tuberculosis complex (MTBC) present in the population are largely unknown.

Objective

The aim of this study was to perform the first genomic analysis of MTBC isolates from Tasmania to better understand the epidemiology of TB in the state.

Methods

Whole-genome sequencing was performed on cultured isolates of MTBC collected from 2014–2016. Single-locus variant analysis was applied to determine the phylogeny of the isolates and the presence of drug-resistance mutations. The genomic data were then cross-referenced against public health surveillance records on each of the cases.

Results

We determined that 83.3% of TB cases in Tasmania from 2014–2016 occurred in non-Australian born individuals. Two possible TB clusters were identified based on single locus variant analysis, one from November-December 2014 (n = 2), with the second from May-August 2015 (n = 4). We report here the first known isolate of multi-drug resistant (MDR) M. tuberculosis in Tasmania from 2016 for which we established its drug resistance mutations and potential overseas origin. In addition, we characterised a case of M. bovis TB in a Tasmanian-born person who presented in 2014, approximately 40 years after the last confirmed case in the state’s bovids.

Conclusions

TB in Tasmania is predominantly of overseas origin with genotypically-unique drug-susceptible isolates of M. tuberculosis. However, the state also exhibits features of TB that are observed in other jurisdictions, namely, the clustering of cases, and drug resistance. Early detection of TB and contact tracing, particularly of overseas-born cases, coordinated with rapid laboratory drug-susceptibility testing and molecular typing, will be essential for Tasmania to reach the World Health Organisation’s TB eradication goals for low-incidence settings.

The changing epidemiology of spinal tuberculosis: the influence of international immigration in Catalonia, 1993-2014

The overall incidence of spinal tuberculosis (TB) appears to be stable or declining in most European countries, but with an increasing proportion of cases in the foreign-born populations. We performed a retrospective observational study (1993-2014), including all cases of spinal TB diagnosed at a Barcelona hospital to assess the epidemiological changes. Fifty-four episodes (48·1% males, median age 52 years) of spinal TB were diagnosed. The percentage of foreign-born residents with spinal TB increased from 14% to 45·2% in the last 10 years (P = 0·017). Positive Mycobacterium tuberculosis testing in vertebral specimens was 88·2% (15/17) for GeneXpert MTB/RIF. Compared with natives, foreign-born patients were younger (P < 0·01) and required surgery more often (P = 0·003) because of higher percentages of paravertebral abscess (P = 0·038), cord compression (P = 0·05), and persistent neurological sequelae (P = 0·05). In our setting, one-third of spinal TB cases occurred in non-native residents. Compared with natives, foreign-born patients were younger and had greater severity of the disease. The GeneXpert MTB/RIF test may be of value for diagnosing spinal TB.