Photo by Heike Alberts

Photo by Heike Alberts

Chapter 11: Integrating Approachesto the Study of the Geography of Health

An Introduction to the Geography of Health

2 An Introduction to the Geography of HealthAnthamatten and Hazen

Although ecological, social, and spatial approaches offer important and unique perspectives to particular health

problems, a combination of approaches is ultimately the optimal way to explore many critical questions.

How could a combination of these approaches be used in investigating the following issues:

a) deciding the location of a new hospital?b) developing a vector-control program for Chagas disease?

Chapter 11

3 An Introduction to the Geography of HealthAnthamatten and Hazen Chapter 11

Programs to control or eradicate infectious diseases often benefit from a combination of approaches.

For the remainder of this PowerPoint we will discuss ways in which combining different geographic approaches to

health could inform infectious disease campaigns.

Global Infectious Disease Campaigns


Policymakers recognize three distinct approaches to tackling infectious disease:

disease control: restricting the circulation of a disease to background levels

disease elimination: the removal of a disease from a particular area

disease eradication: the complete removal of a disease from existence

What kinds of actions or policy can be implemented to achieve the elimination

or eradication of a disease?

What are some of the pros and cons of eradication as opposed to elimination or control?


What factors might influence how easy it is to eradicate a disease?

In theory, all infectious diseases should be eradicable given the right tools (Dowdle 1998); in practice, there

are distinct technical, biological, and social factors that make some diseases easier targets than others.

What makes eradication feasible?


Biological and technical feasibility hinge upon ecological factors such as:

1) the availability of a suitable intervention to interrupt transmission of the disease,

2) humans being central to the life cycle with no other vertebrate or environmental reservoirs,

3) visible symptoms or clear diagnostic tests for identifying individuals with the disease.

A) Eradication must be biologically and technically possible


B) Social conditions, particularly economic and political factors, must favor eradication

“…of all the lessons learned in the past 85 years, none is more important than the recognition that societal and political

considerations ultimately determine the success of a disease eradication effort” Aylward et al. (2000: 1515).

What sorts of social factors might we take into consideration in eradication campaigns?

Which diseases would you suggest might be eradicable, given these criteria?

A) Eradication must be biologically and technically possible


Rank Disease Est. Cases (Date)

Transmission Breaking Cycle

1 Polio (virus) 1936 (2005) Sewage-contaminated water

Oral vaccine (drops)

2 Guinea Worm (worm)

12,000 (2005) Infected drinking water

Filter or treat pond water; dig wells deeper to avoid contamination

3 Lymphatic Filariasis (worm)

120 million (1996)

Mosquitoes De-worming pills; patients must be treated annually for 6 years

4 Measles (virus) 30 million annually

Airborne droplet

Vaccine (injection)

Top Candidates for Disease Eradication

Source: New York Times (2006)




5 Blinding Trachoma (bacteria)

84 million affected; 2 million blind

Spread by flies Antibiotics; access to clean water; covered latrines; surgery in late stages

6 Onchocerciasis (river blindness) (worm)

18 million affected; 500,000 blind

Spread by bite of black flies

Insecticides for flies; de-worming pills for patients

7 Hepatitis B (virus)

350 million carriers

By blood or body fluids

Three vaccine doses

8 Leprosy (bacteria)

2.8 million affected; 1-2 million disabled

Transmission by extended physical contact

Antibiotic triple therapy daily for a year






9 Neonatal Tetanus (bacteria)

200,000 deaths per year; 95% death rate

Umbilical cord cut with dirty blade

Clean delivery practices; vaccine for mother and baby

10 Iodine Deficiency

740 million Goiters in adults; brain damage in fetus

Iodized salt



What commonalities can you identify among these diseases?


“Orphan Diseases” and “Neglected Tropical Diseases”

Ultimately, which diseases get attention is often more of a political or economic decision than a medical one.

The term “orphan disease” is used to refer to diseases that have been neglected because so few people suffer from them,

or the populations that suffer from them are so poor that there is little economic incentive to develop therapies.

Many of these neglected diseases are found in the tropics, owing to the poverty of populations in many tropical regions

—hence the term “neglected tropical diseases.”


Global Infectious Disease Campaigns

Past and ongoing disease eradication campaigns

Dahlem Workshop criteria for feasibility of eradication

Success?

Disease Dates Biologicalfeasibility

Cost–benefit positive

Broad support?

Yellow fever 1915–1977 No No No No

Yaws 1954–1967 No No No No

Malaria 1955–1969 No Yes Yes No

Smallpox 1958–1979 Yes Yes Yes Yes

Dracunculiasis 1980–? Yes Yes Variable ongoing

Polio 1988 –? Yes Yes Variable ongoing

Source: Adapted from Aylward et al. (2000)


Smallpox Eradication

The eradication of smallpox remains a high point in global public health.

In 1979, two years after the last known naturally-transmitted case,

the WHO declared the disease officially eradicated; by 1986,

routine vaccination had ceased in all countries (WHO 2010).

Source: WHO (2010a)


The smallpox eradication campaign from 1967 to 1979 probably cost US$200-300 million, but may have resulted in annual

savings of $2,500 million (Wickett 2002: 69). Another estimate suggests that the

economic benefit of eradicating smallpox may be as high as US$450 saved for every

dollar spent (Barrett 2004: 684).

Source: CDC (1980)


Sadly, over the past 30 years, humankind has not managed to repeat this success with any other human disease.

The ecology of smallpox and the social setting in which it was tackled made it a relatively “easy” target for eradication,

calling into question whether we can repeat this success with any other disease.


Source: Sahagún, B., circa 1585

This illustration from the sixteenth century shows a smallpox victim.

Written descriptions of smallpox date as far back as 400 AD (CDC

2004). The disease may have emerged from an animal poxvirus as early as 10,000 BC (Wickett 2002). The disease is primarily spread by airborne transmission, but can also

be spread via fomites such as infected bedding, although with

much lower transmissibility.


Source: CDC and Conrad (1969)

Smallpox had about a 30% mortality rate, led to

blindness, and left many of those infected

permanently disfigured.

A smallpox sufferer in Dekina, Nigeria, 1969


Source: CDC (1975)

When the WHO’s global eradication program was launched in 1967 there

was still no effective treatment for smallpox.


Source: CDC, Millar (1969)

An effective vaccination was available, however, developed from

a long history of experimentation with smallpox inoculation.

What characteristics of smallpox made it a relatively “easy” target for eradication?


A variety of factors related to the ecology of smallpox made it a good target for eradication.

+ No animal reservoir or vector+ Distinctive symptoms made it easy to

recognize+ People are only at risk when in the

presence of an infected person with obvious symptoms

+ Vaccination is very effective+ Vaccination is easy to administer and

lasts about ten years


The smallpox campaign’s primary goal was mass vaccination of at least 80% of every afflicted population in order to ensure that herd immunity protected the remainder.

Owing to the remoteness of much of the afflicted population, it soon became clear that this goal was unrealistic.

Source: CDC (date unknown)

A poster promoting smallpox and measles vaccination.


The “x”s represent infected people and the “o”s represent the people around them. A

dotted line between two individuals indicates contact between them.

Each circle on the diagram encompasses the individuals who would be vaccinated in a ring vaccination campaign: this comprises the infected person, the infected person’s contacts, and contacts of those contacts.

Fortunately, an understanding of the

disease’s diffusion patterns suggested another strategy:

ring vaccination.


The world’s last naturally-acquired case of smallpox was recorded in Somalia in October 1977.

Today, the virus remains only in several high-security facilities, and some countries continue to

keep stockpiles of the vaccine.

What are some of the arguments for and against keeping stockpiles

of smallpox vaccine?


Polio Eradication

Poliomyelitis (polio) is currently the primary global target for eradication. Policymakers had hoped that the

disease would be eradicated by the year 2000, but isolated pockets persist.

Many ecological and social aspects of the disease make it a more difficult target for eradication than smallpox.


Source: CDC and Farmer (1963)

Polio is a viral disease that is highly infectious. Symptoms include fever, fatigue, headache and

vomiting, making it difficult for a layperson to differentiate mild

cases from a host of other diseases by symptoms alone.

Infection leads to irreversible paralysis in approximately one in 200 cases; among those paralyzed, 5–10% die when breathing muscles

become immobilized.Those who survive may require considerable

therapy to regain physical function.


Source: CDC and Hilpertshauser (1963)

The virus is primarily spread via the fecal–oral route of transmission

and is commonly contracted from contaminated water supplies. The virus is also found at low

concentrations in oral secretions and can be passed directly among individuals through contact with

saliva or airborne droplets.

Although there is no cure for polio, two effective vaccines were developed in the 1950s: an injectable inactivated vaccine

and a live oral polio vaccine (OPV).


Source: WHO (2010d)

The potential to control polio with these vaccines was

quickly realized at a national level and elimination

campaigns were initiated in several countries.

This image shows an infant being vaccinated against polio in Somalia,

which has had recent success in eliminating polio.


Source: WHO (2010d)

The eradication campaign focused on four approaches: • high infant immunization

coverage,• surveillance for wild poliovirus,• laboratory investigation of

paralysis cases in children,• targeted “mop-up” campaigns.

The Global Polio Eradication Initiative was launched in

1988, led by the WHO, Rotary International, the US CDC,

and UNICEF.


Source: CDC, NIP, and Rice, B. (date unknown)

Despite great success, the campaign began to falter between

2003 and 2005 as place-specific challenges became apparent in

remaining pockets of transmission.For instance, in Pakistan and

Afghanistan the remoteness of many populations, conflict, and

cultural resistance to vaccination led to polio outbreaks.

What characteristics of polio make it a challenging target for eradication?


A variety of factors have made polio eradication a challenging goal:• the virus can persist asymptomatically in humans

and in the environment,• the length of the campaign has led to the waning

of political and donor interest,• war and instability have thwarted efforts in some

regions,• significant social resistance has developed to

polio vaccination in some contexts.


Source: WHO (2010b)

In 2010, there were a total of 908 cases of polio worldwide, most of which in Tajikistan, Pakistan, and the Democratic Republic of Congo.


Global campaigns to control disease provide an excellent illustration of ways in which geographic knowledge can be applied to health

problems. Eradication efforts undoubtedly depend on a rich understanding of the ecological, social, and spatial facets of diseases.

A combination of ecological, social, and spatial approaches can similarly provide valuable insights for tackling other health problems.

Conclusion


Discussion Questions

1. Compare the significance of ecological, social, and spatial factors in the relative success of two of the following eradication campaigns: malaria, smallpox, dracunculiasis, and polio. How can geographical approaches to health elucidate the challenges of these campaigns?

2. Considering the ecological, spatial, and social aspects of polio and dracunculiasis, which do you consider to have a greater likelihood of eradication? Taking into account both social and ecological factors, discuss whether you would support control, elimination, or eradication of another disease you know about.

3. To what degree should the rights of the individual be protected in eradication campaigns? In particular, should individuals have the right to decline vaccination for themselves or their children?Why or why not?


Discussion Questions

4. Discuss the advantages and disadvantages of ecological, social, and spatial approaches to health. When might each be useful or show its limitations? What are the pros and cons of a biomedical approach to health?

5. How would you describe the sub-discipline of health geography to a layperson?


ReferencesAylward, R. B. (2006) ‘Eradicating polio: today's challenges and tomorrow's legacy’, Annals of Tropical Medicine and Parasitology, 100: 401–13.

Barrett, R., Kuzawa, C. W., McDade, T. and Armelagos, G. J. (1998) ‘Emerging and re-emerging infectious diseases: the third epidemiologic transition’, Annual Review of Anthropology, 27: 247–71.

[CDC] Centers for Disease Control and Conrad, L. (1969) “Image ID# 7170” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 12 Jan 2010).

CDC and Farmer, C. (1963) “Image ID# 2612” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 01 Dec 2010).

CDC and Hilpertshauser, M. (1963) “Image ID# 7224” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 01 Dec 2010).

CDC and Millar, J. (1969) “Image ID# 1985” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 05 Jan 2011).

CDC, NIP, and Rice, B. (date unknown) “Image ID# 134” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 05 Jan 2011).

CDC. (date unknown) “Image ID# 2564” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 12 Jan 2011).

CDC. (1975) “Image ID# 12291” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 05 Jan 2011).

CDC. (1980) “Image ID# 7079” Public Health Image Library [Online]. Available: < http://phil.cdc.gov/phil/download.asp> (Accessed 30 Nov 2010).


ReferencesCDC. (2004). “Smallpox Disease Overview” Emergency Preparedness and Response [Online]. Available: < http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp>

Dowdle, W. R. (1998) ‘The principles of disease elimination and eradication’, Bulletin of the World Health Organization, 76 Suppl 2: 22–5.

New York Times. (2006) (20 March 2006) Diseases on the Brink [Online]. Available: <http://www.nytimes.com/ref/health/2006_BRINK_SERIES.html>.

Sahagún. B. Florentine Codex.

Wickett, J. (2002) ‘The final inch: the eradication of smallpox and beyond’, Social Scientist, 30: 62–78.

WHO. (2010a) Archives of the Smallpox Eradication Programme [Online]. Available: <http://www.who.int/archives/fonds_collections/bytitle/fonds_6/en/index.html> [Accessed May 07, 2010].

WHO. (2010b) Polio This Week – As of 5 January 2011 [Online]. Available: <http://www.polioeradication.org/Dataandmonitoring/Poliothisweek.aspx > (Accessed 06 Jan 2011).

WHO. (2010c) Smallpox [Online]. Available: <http://www.who.int/mediacentre/factsheets/smallpox/en/> (Accessed 16 March 2010).

WHO. (2010d). Somalia: Three Years Polio-Free. [Online] Available: <http://www.who.int/features/galleries/somalia_photo_gallery/en/index.html> (Accessed 06 Jan 2011).

Photo by Heike Alberts

Documents

Transcript of Photo by Heike Alberts