An Introduction to the Geography of Health Chapter

An Introduction to the Geography of Health Chapter 3: Demographic Change and Emerging and Resurgent Infectious Diseases Photo by Heike Alberts Cairo, Egypt

The Demographic and Epidemiologic Transitions Human population size and structure are clearly influenced by patterns of health and disease. Lifespans have increased and the global population grown very rapidly in recent history. Data from United Nations (2009), United Nations and Department of Social and Economic Affairs (2009) 2 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The United Nations estimates that population growth will not stabilize until at least the mid-twenty-first century. 3 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The Demographic Transition Model Human population size and structure are influenced by patterns of fertility and mortality. 4 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The population growth rate is the difference between the birth rate and the death rate. 5 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

In the first stage, both birth rates and death rates fluctuate at high levels, leading to little or no population growth. 6 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The growing gap between high birth rates and decreasing death rates increases the population growth rate. In stage two, advances in sanitation and medicine lead to a rapid decline in the death rate, but birth rates remain high. 7 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

As the birth rate declines, population growth slows. In stage three, processes of modernization lead to declining birth rates. 8 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Population growth approaches zero as both birth and death rates are now low. In stage four, low birth rates and low death rates mean growth rates remain near zero. 9 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Some scholars have argued that a fifth stage should be added to the model to include industrial societies that are experiencing negative natural growth. 10 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Can you think of examples of countries that fit each stage of the model? 11 Anthamatten and Hazen What limitations or problems do you see with the model? An Introduction to the Geography of Health Chapter 3

Epidemiologic Transition In low-income countries, infectious diseases cause a large proportion of deaths. Low-Income Countries Cause of death Lower respiratory infections Coronary heart disease Diarrheal diseases HIV/AIDS Stroke/cerebrovascular diseases Chronic obstructive pulmonary disease Tuberculosis Neonatal infections Malaria Prematurity and low birth weight Proportion (%) 11. 2 9. 4 6. 9 5. 7 5. 6 3. 5 3. 4 3. 3 3. 2 Data Source: WHO 2008 12 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

With industrialization and greater wealth, the major causes of death shift from infectious to noninfectious diseases. This shift is known as the epidemiologic transition. What are some of the factors that stimulate this health transition? High-Income Countries Cause of death Coronary heart disease Stroke/cerebrovascular diseases Trachea, bronchus, lung cancers Lower respiratory infections Chronic obstructive pulmonary disease Alzheimer and other dementias Colon and rectum cancers Diabetes mellitus Breast cancer Stomach cancer Proportion (%) 16. 3 9. 3 5. 9 3. 8 3. 5 3. 4 3. 3 2. 8 2. 0 1. 8 Data Source: WHO 2008 13 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Many middle-income countries now face a “double burden of disease” in the face of rapid industrialization, as they cope with both infectious disease and diseases of affluence. Middle-Income Countries Cause of death Stroke/cerebrovascular diseases Coronary heart disease Chronic obstructive pulmonary disease Lower respiratory infections Trachea, bronchus, lung cancers Road traffic accidents Hypertensive heart disease Stomach cancer Tuberculosis Diabetes mellitus Proportion (%) 14. 2 13. 9 7. 4 3. 8 2. 9 2. 8 2. 5 2. 2 2. 1 Data Source: WHO 2008 14 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Pathogen and Vector Populations It is not only characteristics of the host population that are important for understanding trends in human infectious diseases. Pathogens and vectors can evolve rapidly, making them a challenging target for drug and vaccine manufacturers. Image source: CDC (1968) A CDC worker working with an influenza virus in 1968. 15 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Antibiotic Resistance Antibiotic resistance emerges when antibiotics kill the most susceptible bacteria in a population. The remaining individuals, with higher levels of resistance to the antibiotic, are able to breed rapidly, thereby increasing the proportion of antibiotic-resistant bacteria in the population. 16 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Although pathogens evolve in this way naturally, humans have unwittingly facilitated the development of antibioticresistant pathogens. How have human activities encouraged the development of antibiotic resistance? Image source: CDC (1976) A vaccination is administered as part of the US swine flu vaccination campaign in 1976. 17 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Resistance to anti-malarial drugs Data from Global Malaria Partnership (2005) In vector-borne diseases, resistance is becoming a problem in both pathogen and vector populations; vectors are increasingly resistant to pesticides. 18 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Emergent and Resurgent Infectious Disease Infectious disease continue to be responsible for more than one-third of deaths worldwide. Additionally, a large number of new infectious diseases have emerged since the 1940 s. The following slides show the spatial distribution of several types of emerging infectious disease over recent decades. How might we explain the patterns we observe? 19 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Adapted from Jones et al. (2008: 993). Reprinted by permission from Macmillan Publishers Ltd: [Nature] (Jones, K. et al. Global trends in emerging infectious diseases. " Nature 451(7181): 990 -994) © 2008 Zoonotic pathogens can cross from wildlife to human populations when humans settle or hunt in wildlands. E. g. , HIV/AIDS may have entered human populations during the butchering of wild monkeys. 20 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Adapted from Jones et al. (2008: 993). Reprinted by permission from Macmillan Publishers Ltd: [Nature] (Jones, K. et al. Global trends in emerging infectious diseases. " Nature 451(7181): 990– 94) © 2008 Zoonotic pathogens from non-wildlife sources typically cross into human populations from agricultural systems. E. g. , domestic poultry were the likely source of pathogens responsible for recent avian flu outbreaks. 21 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Adapted from Jones et al. (2008: 993). Reprinted by permission from Macmillan Publishers Ltd: [Nature] (Jones, K. et al. Global trends in emerging infectious diseases. " Nature 451(7181): 990– 94) © 2008 The emergence of drug resistant pathogens, such as multi-drug resistant tuberculosis, is often associated with overuse or misuse of antibiotics. 22 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Adapted from Jones et al. (2008: 993). Reprinted by permission from Macmillan Publishers Ltd: [Nature] (Jones, K. et al. Global trends in emerging infectious diseases. " Nature 451(7181): 990– 94) © 2008 Many vector-borne diseases, such as dengue fever and malaria, are resurging as resistance develops in pathogen and vector populations. 23 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Diffusion Infectious diseases can be modeled geographically by considering how they spread across space. The spread of something through space is called diffusion. 24 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The spread of a phenomenon across space, passed through interactions between one person and his or her neighbor is called expansion diffusion. The "x" symbolizes the original source of the phenomenon; the circles symbolize settlements—larger circles represent larger settlements. 25 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

The introduction of a phenomenon to a new location, completely outside the current range of that phenomenon, is called relocation diffusion. The "x" symbolizes the original source of the phenomenon; the circles symbolize settlements—larger circles represent larger settlements. 26 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Hierarchical diffusion is the spread of a phenomenon along hierarchical settlement patterns. The phenomenon is more likely to move into large cities before small villages. The "x" symbolizes the original source of the phenomenon; the circles symbolize settlements—larger circles represent larger settlements. 27 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

How would you describe diffusion patterns of the SARS virus? An apparently new virus that emerged in China in 2003 eventually led to outbreaks as far away as Canada. Airline transportation was implicated in the rapid spread of the new disease, named severe acute respiratory syndrome (SARS). 28 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Influenza Human influenza strains are believed to have originated from pathogens that infect birds and pigs. The H 5 N 1 (avian flu) virus is shown in gold. 29 Anthamatten and Hazen An Introduction to the Geography of Health Image source: CDC (1997) Chapter 3

Periodic outbreaks of new strains of influenza can devastate human populations. An influenza pandemic in 1918 may have killed 50 to 100 million people. Image Source: United States Navy (1918 b) Both of these images were taken during World War I. Sneeze screens were erected to prevent the spread of influenza in barracks (above). Soldiers were asked not to spit (left). Image Source: United States Navy (1918 a) 30 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

In March 2009, an influenza outbreak began in Mexico. Popularly referred to as “swine flu, ” the influenza strain responsible (H 1 N 1) was capable of infecting humans, causing concern that a pandemic might follow, although this never transpired. Image source: CDC (2009) 31 Anthamatten and Hazen The H 1 N 1 (swine flu) virus An Introduction to the Geography of Health Chapter 3

Pandemic Influenza Phases Adapted from WHO (2009) Concerns over potential influenza pandemics center on the possibility of a new virus emerging from animals to which humans have little immunity. If this strain were then to evolve the ability to spread among humans, a pandemic could occur, as illustrated here. 32 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Tuberculosis (TB) may have infected human populations since antiquity. It is estimated that one-third of the global population may be infected with TB, but these infections only become active disease under certain conditions. Image source: CDC (1982) 33 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

Tuberculosis is often considered to be a disease of poverty because factors such as poor living conditions and inadequate diet can transform a dormant infection into an active disease. Most active cases, therefore, occur in the low-income world. Global estimated TB incidence, prevalence, and mortality (2005) Incidence Prevalence TB Mortality Number (1, 000 s) Rate (per 100, 000) % of total Number (1, 000 s) Rate (per 100, 000) 2, 529 343 29 3, 773 511 544 74 Americas 352 39 4 448 50 49 6 E Mediterranean 565 104 6 881 163 112 21 Europe 445 50 5 525 60 66 7 SW Asia 2, 993 181 34 4, 809 290 512 31 Western Pacific 1, 927 110 22 3, 616 206 295 17 Global 8, 811 136 100 14, 052 217 1, 577 24 WHO region Africa Adapted from WHO (2007) 34 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

A major problem with TB is that the course of treatment is extremely long and people often stop drug regimens before they are complete. This has led to the development of many drug-resistant strains of TB. Tuberculosis testing at a mobile clinic, 1963 35 Anthamatten and Hazen An Introduction to the Geography of Health Image source: CDC (1963) Chapter 3

In treating drug-resistant strains several different drugs are often administered. Additionally, many places have adopted directly observed therapy (DOTS) to make sure that people complete the drug regimen. Image source: WHO (2002) © WHO/P. Virot 36 Anthamatten and Hazen Directly Observed Therapy (DOTS) in Ethiopia An Introduction to the Geography of Health Chapter 3

Tuberculosis Drug-resistance is a significant problem in high-income contexts as well. Staphylococcus aureus is an example of a nosocomial infection, one that commonly occurs in healthcare settings, that has evolved drug resistant strains. Geographic variation in resistance to methicillin-resistant Staphylococcus aureus (MRSA) Data source: EARSS (2005) 37 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

References [CDC] Centers for Disease Control. (1963) “Image ID# 1438” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 11 August 2010). CDC. (1968) “Image ID# 8165” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 11 August 2010). CDC. (1976) “Image ID# 8372” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 11 August 2010). CDC. (1982) “Image ID# 4716” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 12 August 2010). CDC. (1997) “Image ID# 8372” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 11 August 2010). CDC. (2009) “Image ID# 11214” Public Health Image Library [Online]. Available: <http: //phil. cdc. gov/phil/download. asp> (Accessed 12 August 2010). [EARSS] European Antimicrobial Resistance Surveillance System. (2005) Annual Report, 2004 [Online]. Available: <http: //www. rivm. nl/earss/Images/EARSS%20 annual%20 report%202004%20 webversie_tcm 61 -25345. pdf> (Accessed 26 February 2010). Global Malaria Partnership. (2005) World Malaria Report 2005, Geneva: WHO, UNICEF. Jones, K. E. , Patel, N. G. , Levy, M. A. , Storeygard, A. , Balk, D. , Gittleman, J. L. and Daszak, P. (2008) ‘Global trends in emerging infectious diseases’, Nature, 451: 990– 93. 38 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3

References United Nations. (2009) World Population Prospects: The 2008 Revision, Executive Summary [Online]. New York: United Nations. Available: <http: //esa. un. org/unpd/wpp 2008/pdf/WPP 2008_Executive-Summary_Edited_6 -Oct-2009. pdf> (Accessed 27 December 2009). United Nations and Department of Social and Economic Affairs. (2009) World Population Prospectus: The 2008 Revision Population Database [Online]. Available: <http: //esa. un. org/unpp/index. asp> (Accessed 3 January 2010). United States Navy. (1918 a). “Photo # NH 41731 -A. Influenza precaution sign at the Naval Aircraft Factory, Philadelphia” Naval Historical Center. [Online]. Available: <http: //www. history. navy. mil/photos/images/h 41000/h 41871 c. htm> United States Navy. (1918 b). “Photo # NH 41871. Crowded sleeping area at Naval Training Station, San Francisco, California” Naval Historical Center. [Online]. Available: <http: //www. history. navy. mil/photos/images/h 41000/h 41871 c. htm> [WHO] World Health Organization. (2002) ‘Tuberculosis - DOTS, Ethiopia’ [Online]. Available: <http: //www. who. int/mediacentre/multimedia/2002/eth_tb/en/index 1. html> (Accessed 11 Jan 2011). WHO. (2007) ‘’Tuberculosis’ Factsheet No. 104’ [Online]. Available: <http: //www. who. int/mediacentre/factsheets/fs 104/en/index. html> (Accessed 2 June 2009). WHO. (2008) The Top Ten Causes of Death [Online]. Available: <http: //www. who. int/mediacentre/factsheets/fs 310_2008. pdf> (Accessed 17 April 2010). WHO. (2009) Current WHO Phase of Pandemic Alert [Online]. Available: <http: //www. who. int/csr/disease/avian_influenza/phase/en/index. html> (Accessed 13 May 2009). 39 Anthamatten and Hazen An Introduction to the Geography of Health Chapter 3