Global Health and Epidemiology

Learning Outcomes

  • Apply theories of social epidemiology to an understanding of global health issues
  • Compare and contrast health conditions in high- versus low-income countries

Social epidemiology is the study of the causes and distribution of diseases. Social epidemiology can reveal how social problems are connected to the health of different populations. These epidemiological studies show that the health problems of high-income nations differ greatly from those of low-income nations. Some diseases, like cancer, are universal. But others, like obesity, heart disease, respiratory disease, and diabetes are much more common in high-income countries and are a direct result of a sedentary lifestyle combined with poor diet. High-income nations also have a higher incidence of depression (Bromet et al. 2011). In contrast, low-income nations suffer significantly more from deadly diseases such as malaria and tuberculosis, diseases that are rare in high-income contexts.

How does health differ around the world? Some economic and political theorists, most notably Immanuel Wallerstein, differentiate among three types of countries: core nations, semi-peripheral nations, and peripheral nations. Core nations are those that we think of as highly developed or industrialized, semi-peripheral nations are those that are often called developing or newly industrialized, and peripheral nations are those that are relatively underdeveloped. While the most pervasive issue in the U.S. healthcare system is affordable access to healthcare, other core countries have different issues, and semi-peripheral and peripheral nations are faced with a host of additional concerns. Reviewing the status of global health offers insight into the various ways that politics and wealth shape access to healthcare, and it shows which populations are most affected by health disparities. As we move across international contexts, it is imperative to keep in mind the influence of cultural significance on health, as it is a mechanism that plays a role in the conceptualization of health conditions, the role of healthcare and its providers, and the consequences of illnesses.

Try It

Health in High-Income Nations

Obesity, which is on the rise in high-income nations, has been linked to many diseases, including cardiovascular problems, musculoskeletal problems, diabetes, and respiratory issues. According to the Organization for Economic Cooperation and Development (2011), obesity rates are rising in all countries, with the greatest gains being made in the highest-income countries. The United States has the highest obesity rate at 42 percent; some of these people are considered severely obese, which occurs in 9 percent of U.S. adults (Hales 2020).

Wallace Huffman and his fellow researchers (2006) contend that several factors are contributing to the rise in obesity in developed countries:

  • Improvements in technology and reduced family size have led to a reduction of work to be done in household production.
  • Unhealthy market goods, including processed foods, sweetened drinks, and sweet and salty snacks are replacing home-produced goods.
  • Leisure activities are growing more sedentary, for example, computer games, web surfing, and television viewing.
  • More workers are shifting from active work (agriculture and manufacturing) to service industries.
  • Increased access to passive transportation has led to more driving and less walking.

Obesity and weight issues have significant societal costs, including lower life expectancies and higher shared healthcare costs. While the United States fares well in terms of health outcomes, it actually has a relatively shorter life expectancy than countries similar in economic development, standards of living, and wealth,[1] which is partially due to obesity and its consequences.

While ischemic heart disease is the single most prevalent cause of death in higher-income countries, cancers of all types combine to be a higher overall cause of death. Cancer accounts for twice as many deaths as cardiovascular disease in higher-income countries (Mahase 2019).

Watch It

This video explains population health and describes some of the key health indicators that measure health for different populations. Consider what factors contribute to health disparities among populations.

Health in Low-Income Nations

Children’s protruding bellies are shown here.

Figure 1. In low-income countries, malnutrition and lack of access to clean water contribute to a high child mortality rate. (Photo courtesy of Steve Evans/flickr)

In peripheral nations with low per capita income, it is not the cost of healthcare that is the most pressing concern. Rather, low-income countries must manage such problems as infectious disease, high infant mortality rates, scarce medical personnel, and inadequate water and sewer systems. Due to such health concerns, low-income nations have higher rates of infant mortality and lower average life spans.

In addition to these challenges, and largely because of these challenges, underdeveloped regions face epidemics of disease. As was mentioned in the introduction, several countries in Africa have dealt with the spread of Ebola in the last 5 years, and the Democratic Republic of the Congo is currently trying to address an Ebola epidemic. The Ebola  epidemic is not the result of a single factor, but instead is the consequence of a combination of them, ranging from the lack of a cure, to Ebola being highly infectious and difficult to diagnose, to its being coupled with structural contexts of underdeveloped health systems, lack of workers, stigmatizing cultural beliefs, and migratory practices.


Hear about Ebola’s effects and consequences during the height of the epidemic, as well as the context in which Ebola-infected individuals seek assistance.

The Zika virus, which was first discovered in Uganda over 6 decades ago, has resulted in recent outbreaks in the Pacific Islands and Brazil and in a widespread epidemic in 2015-2016. The virus causes Zika fever, which is a mild illness with symptoms such as a fever and a rash, but as the disease became more common, evidence suggested that the virus was also connected to Guillain–Barré syndrome in adults, as well as birth defects and other neurological problems. The virus can be transmitted from an infected pregnant woman to her fetus, then can cause microcephaly (an abnormally small head) and other severe brain anomalies in the infant. The virus is spread mainly by the Aedes aegypti mosquito, which is commonly found throughout the tropical and subtropical Americas, and in parts of the southern United States. It can also be spread by the Aedes albopictus (“Asian tiger”) mosquito, which is distributed as far north as the Great Lakes region in North America. Men infected with Zika can transmit the virus to their sexual partners.


Learn about the spread of the Zika virus—and beware of massive soccer events! The Zika virus is said to have begun its recent spread after visitors flocked to Brazil for the World Cup in 2014. Some athletes even declined to participate in the 2016 Summer Olympics in Rio de Janeiro, citing ongoing concerns about the virus and its impact on fetal development.

You can see a descriptive transcript of “Animated Map of Zika’s Spread” (link opens in new window).

One of the biggest contributors to medical issues in low-income countries is the lack of access to clean water and basic sanitation resources. According to a 2014 UNICEF report, almost half of the developing world’s population lacks improved sanitation facilities. The World Health Organization (WHO) tracks health-related data for 193 countries, and organizes them by region. In their 2019 World Health Statistics report, they document the following statistics:

  • Globally in 2019, the rate of mortality for children under five was 38 per 1,000 live births, which is a dramatic change from previous decades. (In 1990, the rate was 93 deaths per 1,000 births (World Health Organization 2020.)) In low-income countries, however, that rate is much higher. The child mortality rate in low-income nations was 11 times higher than that of high-income countries—76 deaths per 1,000 births compared to 7 deaths per 1,000 births (Keck 2020). To consider it regionally, the highest under-five mortality rate remains in the WHO African Region (74 per 1000 live births), around 9 times higher than that in the WHO European Region (8 per 1000 live births) (World Health Organization 2021).
  • The most frequent causes of death in children under five years old are pneumonia, diarrhea, congenital anomalies, preterm birth complications, birth asphyxia/trauma, and malaria, all of which can be prevented or treated with affordable interventions including immunization, adequate nutrition, safe water and food and quality care by a trained health provider when needed.

The availability of doctors and nurses in low-income countries is one-tenth that of nations with a high income. Challenges in access to medical education and access to patients exacerbate this issue for would-be medical professionals in low-income countries (World Health Organization 2011).

Think It Over

  • Study these maps on global life expectancies. What trends do you notice?
  • If social epidemiologists studied the United States in the colonial period, what differences would they find between now and then?
  • What do you think are some of the contributing factors to obesity-related diseases in the United States?

Try It


social epidemiology:
the study of the causes and distribution of diseases


Did you have an idea for improving this content? We’d love your input.

Improve this pageLearn More

  1. OECD (2019), Life expectancy at birth (indicator). doi: 10.1787/27e0fc9d-en (Accessed on 02 April 2019)