The global movement of people, whether within borders or across them, is growing. As of 2020, worldwide estimates indicated that roughly 281 million individuals were international migrants, making up 3.6% of the global population. This number represented an increase of 128 million from 1990 and was over three times the estimated count in 1970. ⁶

Migration is determined by various determinants or drivers of individual and population mobility. The decision to migrate is influenced by circumstances in countries of origin, transit, and destination. Drivers of migration include economic, demographic, environmental, social, and political factors. People often move to improve their quality of life, access better opportunities for work or education, or escape conflict, violence, instability, persecution, or crises. Because urban centers are often seen as providing opportunities and better security, migration can contribute significantly to urban expansion.

The various types of migration contribute differently to urban growth and diversity in various contexts. International migration contributes to cultural diversity in high-income countries. Immigration adds to urban population growth, and in some contexts more so than growth from natural increase. Where both are high, as in some low-income countries, exceptionally high rates of urban growth are observed.

Frequently, migrants in megacities live in informal settlements and makeshift camps and, increasingly, intermediary cities also let unplanned settlements grow unchecked. Such living conditions place migrant populations at risk of poor health outcomes. More importantly, a lack of anticipatory planning, zoning, and building of infrastructure can lead to the costly and inefficient extension of services and more adequate shelter as an afterthought. ⁷ In addition, policy fragmentation across local and national levels may discourage health-oriented urban planning if city governments responsible for other essential services are not as accountable for health as are national health authorities.

Current estimates indicate that 169 million people are international migrant workers ⁸ – a figure that does not include the millions of internal migrant workers, nor refugees and forcibly displaced populations who become migrant workers in urban areas. And yet, extraordinarily little attention, and less action, focuses on migrant workers, despite figures that indicate that migrant workers are more than three times more likely than non–migrants to be in conditions of forced labour. ⁹ A systematic review found that compared with non-migrant workers, migrant workers were 45% less likely to use any health services. ¹⁰ Migrant workers, whether cross-border or internal migrants, are also over-represented in industries exposed to higher risk of occupational injury and fatality. ¹¹

At least 10.1% of all international migrants are children, and many of them migrate unaccompanied or become separated from their parents. ⁶ Apart from sharing the vulnerabilities experienced by adults, children in urban centers are at an increased risk of, at minimum, homelessness, becoming exposed to hunger and violence, and being coerced into panhandling and micro-trafficking. ¹² Although rural-urban migration is more common among younger people, growing numbers of people aged 60 years and older are moving to urban areas around the world. ¹³

The Dahlgren and Whitehead model of the social determinants of health includes different factors that can affect and impact health – including individual, lifestyle, social and community factors and working and living conditions. ¹³ The WHO Commission on Social Determinants of Health (2008) requested that urban governance and planning explicitly address equity, as cities can concentrate threats to health.

Social and structural determinants of health substantially influence the health and the integration of migrant populations in urban settings. For example, state regulations that fail to provide migrants with basic services, including safe housing, social protection, and healthcare, set the foundation for poor health outcomes. Other structural issues, like the segregation of migrant communities in less desirable neighborhoods on the outskirts of many cities, contribute to a lack of access to services and generate new health risks, for example those associated with long commutes or neighborhood safety or environmental hazards.

Intersectional considerations often further increase risks for many migrants. For example, inequitable gender norms sustain isolation and abuses experienced by female migrants. Female migrants, especially asylum-seeking and refugee women and girls, are particularly vulnerable to physical and sexual violence ¹⁴ and early or forced marriage. ¹⁵ Migration-related discrimination can amplify pre-existing gender inequalities, leaving abuse survivors less able to access protection or services for sexual, reproductive, and mental health. Even where social protection is ensured, access to healthcare services may be influenced by migratory status in other ways. International migrants, especially those in marginalized situations, may face sociocultural challenges such as language barriers and lack of familiarity with the health system, ¹⁶ as well as a lack of culturally appropriate services.

In some countries, “health navigator” programs train and certify community health workers to provide free assistance to migrants in their own language. Mobile phone health tools can also support the interventions of community health workers ¹⁷ in countries with high mobile phone coverage, including by teaching the local language to improve health literacy. Community centers are also important health promoting sites, providing access to computers, internet, and other digital resources, for example. Here, migrants can access health information and communicate with government agencies and other organizations (including to schedule healthcare appointments). Such centers can also provide other services important to health such as safe spaces to socialize, play and engage in physical activity that may be scarce in urban environments. Ultimately, greater connectivity and community center-based engagement are also useful to encourage and support participation in the decision-making processes of government agencies and other organizations to better address the needs of migrant populations.

Integration in host communities is a significant issue for many migrants, who often experience disadvantage relative to native residents in many aspects of daily life. ¹⁸ Migrant populations can encounter challenges with respect to adaptation and integration, including competition and conflict among people, groups, and cultures. Adjusting to a new urban lifestyle can mean supplementing, or at times replacing, old social support systems and cultures with new ones. Challenges like securing housing, finding work, and dealing with peer pressure from family and relatives can lead to heavy psychological burdens and resulting mental health challenges ¹⁹ like anxiety, despair, tension, low self-esteem, and loss of control. ²⁰ Among the many factors affecting mental health, the social environment has been shown to have a significant impact. ²¹

Social cohesion, which describes the degree of comradery and solidarity within a community, ²² can be crucial in promoting the mental health and general wellbeing of migrants. Strong social cohesion can give people a sense of support and belonging, which can act as a protective barrier against the negative effects of trauma and displacement. Programs for linguistic and cultural orientation, community-building initiatives, and specialized mental health interventions are a few examples of supportive approaches to build cohesion. Social cohesion can affect migrants’ mental health through three general mechanisms. ²³ First, it can encourage health-related activities and norms and exerts social control over deviant behaviors. Second, it can promote social organization, making it simpler for people to access health services. Third, it can influence psychosocial processes like offering emotional support, raising self-esteem, and fostering mutual respect. In addition, communities where people trust one another are more likely to offer assistance and support, which can help to promote mental health. ²⁴

To promote urban health that genuinely includes migrants, changing the functioning of the health system alone, while crucial, is insufficient. For instance, reducing high risks of road traffic fatalities or respiratory disease due to air pollution among migrant workers depends not only on including them in data collection by health information systems, design of appropriate health promotion information, and access to health services, but also on policy decisions within the transport, energy, and planning sectors, among others. And, vice versa: even if health promotion activities and health services are geared to include migrant workers, services may go unused without accurate data about which groups of workers are affected and how to reach specific groups, such as day laborers, who may be reluctant to lose wages to seek care.

Figure 1 proposes a migrant-inclusive urban health framework to indicate various systems that might interact to affect the health of migrants. The outer spheres of Figure 1 represent multiple systems that can affect health beyond the health system alone. At the centre are “people”, “communities,” and “cities” to indicate that these systems behave in ways that affect individual migrants, migrant subgroups (as defined by nationality, legal status, work sector, etc.) and the health patterns of urban populations of migrants and non-migrants. These systems can also influence epidemiological risk and outcome patterns (e.g., infection and non-infectious diseases, nutrition, mental health) that include or exclude migrant groups and determine how well health information systems track disease patterns. Similarly, actions of multiple systems, such as immigration systems, health systems and employment practices, often combine to determine whether migrants are exposed to health hazards, whether they know their rights and entitlements and whether they work in safe and fairly paid jobs. Finally, civil society often fills in gaps where health systems or government services are not available for migrants.

The systems framework suggests that creating inclusive urban health will require going beyond health sector services, and addressing the important integration influences, such as social networks and community engagement, which can provide highly valued psycho-social support and help communicate health-related information. ²⁵ Central to all these health-inducing factors are legal structures and budget allocation systems to support migrant health amidst increasing urbanization. Evidence suggest that these frameworks are crucial in ensuring migrant health: non-health-targeted public policies can significantly affect migrant health. ²⁶ This underscores the need for a holistic approach to migrant health that considers the broader policy environment. Policies that promote social inclusion, provide easier access to healthcare, and support economic integration can significantly improve health outcomes for migrants.

A strategic and integrated approach to migration and urban health ²⁷ must rely on the recognition that migration health is influenced by decisions made at various levels, from global to local, within and beyond the health sector. The ethical challenges in these decisions impact the provision and accessibility of healthcare services; it is crucial to consider specific ethical dimensions and vulnerabilities in each context. ²⁸ Values such as solidarity, duty, equity, trust, and reciprocity, are central to addressing the health needs and rights of migrants.

Moreover, migration requires effective multilevel governance of migration-related issues at local, national, and international levels. At the local level, this means building alliances and partnerships, raising awareness in the population, and supporting the development of migrants’ potential in their new home. In many contexts, the spontaneous formation of numbers of local, voluntary associations and groups is quite common, driven by a moral duty of care. These can be extremely valuable because they develop detailed knowledge and respond quickly during emergencies. Local authorities need to support and involve such groups, especially where emergencies become prolonged. Because such groups often support undocumented migrants, on the edge of legality, they may be excluded from government action, yet this may set up serious tensions and conflicts within the local population.

To address this multiplicity of influences requires a holistic approach that encompasses all aspects of migrant health, including decent housing, access to basic services, social participation, decent work, emergency preparedness, and mutual support and social cohesion with native populations. A holistic approach transcends the strictly medical aspects of health care, recognizing the importance of a broader perspective for achieving migrant health in all aspects of their lives, and therefore public health for all. Promoting healthy lifestyles and prevention among migrants is also critical to long-term health trajectories, as exemplified by the long-term experiences of the WHO Healthy Cities project. ²⁹