Migration Flow and Its Impact on Tuberculosis Notification in Portugal

Abstract

Introduction

Tuberculosis notification in Portugal has decreased in the last few years. As a consequence of the economic crisis, emigration has increased and immigration has decreased. Immigrants are a risk group for tuberculosis. Most emigrants are 20–44 years old and belong to the age group most affected by tuberculosis.

Objective

To describe the decrease in tuberculosis notification in Portugal over the last years from a demographical point of view.

Methods

Mathematical analysis was performed to quantify the effect of the migration movements (separately and simultaneously) on tuberculosis notification in Portugal from 2008 to 2014. We calculated the estimated tuberculosis notification for each year during the period of study: 1) fixing immigration rate and tuberculosis rate in immigrants at 2008 values; 2) fixing emigration rate and tuberculosis rate in emigrants at 2008 values; 3) fixing both phenomenons at 2008 values.

Results

The differences between the observed and the estimated numbers were small (≤0.5 cases/100 000 inhabitants).

Discussion

Impact of the migration movements on tuberculosis notification rate does not seem to be significant when analyzed for each phenomenon individually and simultaneously, by our model. This might mean that we have to concentrate our efforts in other risk factors for tuberculosis.

Resumen

Introducción

La notificación de casos de tuberculosis en Portugal ha disminuido en los últimos años. Como consecuencia de la crisis económica, la emigración ha aumentado y la inmigración ha disminuido. Los inmigrantes son un grupo de riesgo para la tuberculosis. La mayoría de los emigrantes tienen entre 20 y 44 años y pertenecen al grupo de edad más afectado por la tuberculosis.

Objetivo

Describir la disminución de la notificación de casos tuberculosis en Portugal en los últimos años, desde un punto de vista demográfico.

Métodos

Se realizó un análisis matemático para cuantificar el efecto de los movimientos migratorios (por separado y simultáneamente) en la notificación de casos de tuberculosis en Portugal de 2008 a 2014. Se calculó la notificación de casos de tuberculosis estimada para cada año durante el período de estudio.

La notificación estimada de tuberculosis para cada año del periodo de estudio se calculó: 1) fijando las tasas de inmigración y de tuberculosis en inmigrantes con datos del año 2008; 2) fijando las tasas de emigración y de tuberculosis en emigrantes con datos del año 2008, y 3) fijando ambos fenómenos con datos del año 2008.

Resultados

Las diferencias entre los valores observados y los valores estimados fueron pequeñas (≤ 0,5 casos/100.000 habitantes).

Discusión

Según el modelo matemático propuesto en este trabajo, el impacto de los movimientos migratorios en la tasa de notificación de casos de tuberculosis en Portugal no parece ser significativo cuando se analiza cada fenómeno tanto individual como simultáneamente. Estos datos indicarían que deberíamos concentrar los esfuerzos en identificar otros factores de riesgo para la tuberculosis.

Introduction

Since WHO declared tuberculosis (TB) a global emergency, many efforts have been made worldwide to decrease TB incidence.¹ In Portugal, a TB National Programme was implemented in 1995 and in 2006 the “STOP TB strategy” was launched to delineate specific goals and strengthen the struggle towards the end of TB.2, 3

Eight years later, in 2014, Portugal reached the threshold of low incidence, registering 20 new cases per 100 000 inhabitants.⁴ Despite this, it remains the highest incidence country in the Western Europe and some areas still have an intermediate incidence. Lisbon and Oporto are the districts with the highest incidence.4, 5

Homeless people, drug users, prisoners and migrants are at increased risk of developing TB. These groups concentrate in urban settings and their numbers tend to have an impact on TB.6, 7, 8, 9, 10 This work concentrates solely on the migrant movements’ effect on TB. In fact, in many European countries, most cases of tuberculosis occur within the immigrant population. About 26.8% of TB cases reported in the European Union (EU) and European Economic Area countries are of foreign origin.⁵ Therefore, migrants from high incidence countries have a considerable impact on the tuberculosis burden in low incidence countries.5, 10 Increased risk of TB in this group might be related to higher exposure in the country of origin and/or worse socioeconomic conditions, comparing to the resident population.¹¹

As opposed to other European countries, like Iceland, Cyprus, Norway or Sweden, where more than 70% of tuberculosis cases occur in foreign born individuals, in Portugal, this group represents only about 16% of cases.6, 10, 12 Nevertheless, TB incidence among immigrants in Portugal is much higher than in non-immigrants and it has been increasing.¹³

As a consequence of the economic crisis, in the last few years, an increasing number of individuals have left the country to live abroad. Portugal is the EU country with the largest number of emigrants per capita.¹⁴ In 2014, the number of emigrants had risen to the double, compared to 2008. The majority are young adults, aged 20–44 years old, that left Portugal seeking for better working and living conditions abroad.15, 16 This age group overlaps with the one most affected by TB, between 25 and 54 years old.⁴

The main aim of this study is to describe the decrease in TB in Portugal over the last years purely from a demographical point of view. As such, the authors quantify the effect of the migration movements (immigration and emigration) on the TB notification in Portugal (from 2008 to 2014).