Basic Concepts in Public Health

and Tropical Medicine[Infectious Diseases and Public Health 101]

(mainly in relationship to parasitic diseases)

Daniel G. ColleyMedical Parasitology; CBIO 4500/6500

19 January, 2010

Disease (due to an infectious agent) is what may happen while your immune response tries

to control an infection;

Disease may be the final outcome if your immune system either fails, or over reacts.

Infection does not necessarily equal disease

Important words to define:

Asymptomatic/Morbidity/Mortality

What are the

Scariest InfectiousThreats?Bioterrorism (anthrax; sm’pox; etc.

Pandemics (influenza; plague;..)

Nosocomial Infections; Community Acquired MRSA

Ebola; WNV; SARS; Lyme; Hanta; Cryptosp; Cyclospora; E. coli 0157/H7

Mass Casualty Events

• Intentional – Bioterrorism (Anthrax, Smallpox…..)

• It does not really need to kill to cause terror…

• Unintentional– Pandemics (The Plague, Influenza….)

DYNAMICS OF A HYPOTHETICAL BIOLOGICAL ATTACK

DATE CASES

• 9/12 1

• 9/18 6,674

• 9/23 12,604 (727 deaths)

In 6 mos, 25% of the population will be infected 4% of the Population will die

H1N1 INFLUENZA as it occurred in 1918

• Camp Devens, MA , 1918 Cases 9/12 1 9/18 6,674 9/23 12,604 (727

deaths)

• U.S. 25% of Civilian Population Infected4/100 Died

• Global: In 6 months 20 million deaths (maybe as many

as 40 million)

In 4 years of WWI, 15m deaths; 95% military, 5% civilian

In 8 years of WWII, 50m deaths; 33% military, 67% civilian

Mortality due to Infectious Diseases in the United States, 1900-1996

0

200

400

600

800

1000

1900 1920 1940 1960 1980

Year

Mo

rta

lity

Ra

te p

er

100

,000 20th Century Flu Pandemics

1918 > 500,000 U.S. deaths > 20,000,000 deaths

worldwide (H1N1)

1957 ~ 70,000 U.S. deaths ~ 1,000,000 – 4,000,000 worldwide (H2N2)

1968 ~ 33,000 U.S. deaths ~ 750,000 deaths worldwide (H3N2)--------------------------------------------------

-201? ~ ??? (H5N1??; H1N1?? )

Vigilance is the price of freedom……..

International Co-circulation of 2009 H1N1 and Seasonal Influenza (as of January 04, 2010)

H1N1 as of 01/05/10 – in the USA: 37,778 hospitalizations; 1,735 deaths (lab confirmed) – estimated 20%-infected

Percentage of outpatient visits for Influenza-like Illness (through ILINet)

Antimicrobial Resistance• PROBLEM = Selection Pressure• SOLUTIONS…..

– Reduce infections (handwashing, vaccines, etc.) – Judicious use of antibiotics (not every ear ache)– Limit human antibiotic use in animals – Combination therapy– Target virulence factors– Competitive exclusion

Hospitals are wonderful places when you need them – but be aware they can kill you

At least 20,000 people die of nosocomial infections/year – in the USA

….and this number is rising………… Can you say “MRSA”? Can you say “CA-MRSA”?

Parasites, too: Time to Development of Resistance to Antimalarial Drugs

1940

Chloroquine 16 years

Fansidar 6 years

Mefloquine 4 years

Atovaquone 6 months

1950 1960 1970 1980 1990

Some Emerging (Emerged)

and Re-emerging Infections • Lyme Disease (and other tick-borne diseases)• Dengue Fever (and DHF), WNV, SARS• Hantavirus, Ebola virus and a slew of other HFs• HIV/AIDS• E. coli 0157:H7 CryptosporidiosisCryptosporidiosis CyclosporiasisCyclosporiasis African TrypanosomiasisAfrican Trypanosomiasis Drug-resistant MalariaDrug-resistant Malaria

Focally there are many others Focally there are many others (even schistosomiasis…)(even schistosomiasis…)

Major Factors Contributing to the Emergence of Infectious Diseases

1. Human demographics and behavior

2. Technology and industry

3. Economic development and land use

4. International travel and commerce

5. Microbial adaptation and change

6. Breakdown of public health measures

Institute of Medicine Report 1992

The concepts of Public Health sometimes differ from the concepts of individual medical care,… and the skills are often different, too

They are not mutually exclusive, but they are also not the same

-- Public Health deals with populations, prevention and policy --- and includes research on all of these

-- Public Health often involves the treatment of individual patients, but that is NOT its focus-- At its core, public health is concerned with populations at risk, not individual medical care

[Artemisinin vs. Artemisinin-based combination therapy (ACTs) (when WHO issued a call for companies to stop marketing single treatments of artimisinin)

Epidemiologic terms we need to know

• Incidence of infection– Rate of infection (# new cases/year)

• Prevalence of infection– Proportion of population infected (%)

• Intensity of infection– Level of infection (# worms/patient)– Severity of infection (morbidity/mortality)

• Infectious disease Surveillance– Systematic collection, analysis and use of data on a given

infectious disease

Major Types of Public Health Activities

• Surveillance• Outbreak investigation• Reference diagnosis and consultation• Research (bench-to-field-to-prevention)• Technical assistance & training (lab & epi)• Initiate & support implementation projects• Health policy and Health communication

[Philosophically founded on Epidemiology]

Done at the Global (WHO), Bilateral, Federal (CDC), State, and Local Levels – which takes enormous effort to coordinate (due to money; politics; egos)

Major Parasitic Disease Threats

• Major Killers– Malaria; ~400M– Chagas’ disease;

18M– African

Trypanosomes;

~0.5M– Visceral

Leishmaniasis;

~4M

• Impair Development/Quality of Life– Lymphatic filariasis - 120M– Geohelminths - 2B– Schistosomiasis – 200M– Onchocerciasis – 18M– Cysticercosis ? 50M tapeworm

– Waterborne/Foodborne protozoans – 1.5B

– Cutaneous Leishmaniasis; 8M– Guinea worm – 4M < 15K

A full 747 crashes (~ 430 dead) (fictional disaster)

7 747 crashes every day all year (~ 1,100,000 dead)

Earthquake (7.6R) in Pakistan (10/05) (~80,000 dead)

14 such earthquakes per year (~ 1,120,000 dead)

Earthquake (7.0R) in Haiti (01/10) (~200,000???dead)

5 such earthquakes per year (1,000,000 dead)

Tsunami in Southeast Asia (12/04) (~ 225,000 dead)

5 such tsunami per year (~ 1,125,000 dead)

Each year 1-2 million children die of malaria

What does it take for 1 million people to die a year ???

HEALTH & ECONOMIC BURDEN OF MALARIA

• ~2.5 Billion (40% World’s Population) At Risk

• 400-900 million febrile infections/year

• 1 – 2 million deaths/year, >75% African children• ~4 die per minute~4 die per minute• ~5000 die per day~5000 die per day• ~35,000 die per week~35,000 die per week

• <20% come to attention of the health system

• Pregnant women at high risk of dying, low birth weight children

• Children suffer cognitive damage and anemia

• Families spend up to 25% of income on treatment – (regressive tax)

– Major Impediment to Economic Growth and Development, as well as health

Human Parasitic Diseases with Major Public Health Impact

• International– Malaria– Schistosomiasis– Filariasis (Oncho &

Lymphatic)– Geohelminths– Enteric protozoal diseases– Trypanosomiasis (Afr &Amer)– Leishmaniasis– Neurocysticercosis

– Echinococcosis

– [Dracunculiasis]

• Domestic (USA) +– Cryptosporidiosis– Giardiasis– Neurocysticercosis– Toxoplasmosis– Trichomoniasis– Cyclosporiasis– “Pneumocystis

pneumonia”

– Head lice

– Delusional parasitosesNaeglaria is not on the list (small numbers), but perceptions can control what gets considered “public health”……

Worms are not ProtozoansProtozoans are not Worms

• Worms are bigger than protozoans

BUT -- The biggest difference, in terms of “host/parasite” relationships is:

MOST WORMS DO NOT MULTIPLY IN THE BODY

• The “infection/disease” dynamic is very different in a helminthic infection vs. a protozoal infection

• Both medical and public health approaches to controlling these diseases may have to differ accordingly

Levels of Limiting Parasitic Diseases or their Consequences

• Control (Infection/Transmission vs. Morbidity)

• Elimination of disease (as a public health problem)

• Elimination of infections (in a defined geographic area)

• Eradication (no longer “out there”)

• Extinction (no longer anywhere)

Conceptual (and practical) differences:– Existence vs. Transmission vs. MorbidityThese are hard and fast definitions that (unfortunately) even their makers

ignore when it suits them……current situation in Chagas’ and Malaria

Decision Making: Eradication/Elimination/Control

• Ability of available tools (vaccines, drugs, Dxs, etc.)

• Epidemiologic vulnerability: ability to implement available tools in a

cost- effective manner.

• Availability of sustained funding ($$$, ¥¥¥, etc.).

• Political will:– Burden of disease– Perception and promotion of outcome– Impact on over all health services sector– Impact on over all development– Luck

Essential Partnerships • Multinationals: WHO/HQ; WHO/ROs;WHO/WRs;

UNICEF; UNDP; World Bank

• Bilaterals: JICA; USAID; DFID; GTZ; SIDA, NHDI ….

• Government Agencies: MOHs; CDC; Peace Corps,...

• NGOs: Rotary; Lions; Carter Center; Kiwanis, MSF; ….

• Foundations: WT; EMCF; BWF; B&M Gates; ….

• Industries: Merck; SmithKline Beecham; DuPont, American Cyanamid; Precision Fabrics; Norsk Hydro, ….

In many ways these essential partnerships require the most attention, or the real stuff doesn’t get done

Current Status of Global Parasitic Disease Erad/Elim/Cont Efforts

Ongoing• Dracunculiasis (Guinea Worm) – Eradication• Onchocerciasis – Control• Lymphatic Filariasis – Elimination• Chagas disease – “Erad”/”Elim”/Control• Malaria – Control (RBM) [B&MGFdn – Erad]

Now being “integrated”• Schistosomiasis – Control• Soil-transmitted helminths – Control• Trachoma – Elmination

Possibles• Taeniasis & Cysticercosis – Eradication• Echinococcosis; Elimination• African Trypanosomiasis; Control

•

EradicationPolio (virus)Measles (virus)

Elimination (as “a public health problem”)

Leprosy (bacterium)

Other infections:

Dracunculus medinensis (Guinea worm)

Guinea worm being removed in Zabzugu-Tatale, Ghana; 2000

Guinea Worm Dracunculiasis Eradication

• Coordinating Programs:– WHO; UNICEF; Peace Corps; World Bank; NGOs;NHDI – Global 2000/Carter Center; B&M Gates Fdn ($28.5M)– WHO Collaborating Center (CDC)– Industrial partners

• Critical Elements:

– Community-level health education– Safe water: Borehole or scoop wells; Rx source water

(temephos); Filter water (nylon nets; PVC pipe filters)

– Case Containment, plus rewards

– Regional/Country/Local (village level) commitment

– Monthly reporting and feedback

– Coordination and financing NO Vaccine; NO Drug --- just very hard work, with NO letting up

Progress in the Eradication of Dracunculiasis (Guinea Worm)

• 1981 -- > 4,000,000 cases• 1986 -- 3,500,000 cases• 1989 -- 890,000 cases• 1992 -- 374,000 cases• 1995 -- 129,000 cases• 1998 -- 79,000 cases (61%, Sudan)• 1999 – 80,000 cases (70%, Sudan)• 2000 -- 70,000 cases (73%, Sudan)• 2001 -- 60,000 cases (78%, Sudan)• 2002 -- 50,000 cases (74%, Sudan)• 2003 -- 31,000 cases (62%, Sudan; 27%, Ghana)• 2004 -- 16,026 cases (45%, Sudan; 45%, Ghana)• 2005 – 10,674 cases (52%, Sudan; 37%, Ghana)• 2006 -- 25,217 cases (82%, Sudan; 16% Ghana)• 2007 -- 10,053 cases (63%, Sudan; 33% Ghana)• 2008 -- 4,615 cases (78%, Sudan; 11% Ghana)• 2009 -- 3,147 cases (85%, Sudan; 8% Ghana) [Down from 20 to 5 countries]

Sudan (2690), Ghana (242), Mali (186), Ethiopia (24) Niger (5)

A few images from a “guinea worm trip” to Zabzugu-Tatale, Ghana with Sue Maclain

Where the real work gets done

What are the major challenges to Guinea Worm eradication?

• It requires behavior change !!!– People need to stay out of the water when

they have lesions – and this is NOT easily done!– People need to filter their water through

nylon nets

Largely this depends on knowledge & alternatives • Other aspects are organizational, financial, technical,

political and all these involve tenacity

Photos from a NYT series

“Integrated Disease Control Programs”Integrated is the new buzz word and sounds great…but…

how to do it is the challenge

• Packages of multiple current intervention programs that can be safely, effectively and economically delivered together

Paradigm shift away from single disease model to an “integrated model”Poverty reduction should be moving in a package, not a list of “single interventions”“Turf Wars” need to be worn down and treaties signed

(1st they need to be acknowledge……)

WHO needs to coordinate “compatible partnerships”The driving force should be to “Maximize Coverage”

Combinations of available intervention tools: Drugs-Insecticides-ITNs-Supplements-Vaccines

But a new day has dawned in global disease efforts

Do you know these public

health workers?

It really is a “new day” in terms of global public health

It involves:

Huge involvement of major foundations

Public/Private Partnerships – drug development, etc.

Focus on diseases of poverty

More (but not yet enough) coordination by agencies, governments, NGOs, foundations, people..

BUT: There are some real challenges to getting it done

Implementation – i.e, Just getting on with it Donor fatigue – it takes a long, sustained effortDrug resistance – the threat of any drug- based anti-infectious disease

program - especially with a single drugMonitoring ??Research ??Research ??

Challenges to Understanding and Controlling Parasitic Diseases

• BROAD SCIENTIFIC CHALLENGES– Vaccine development– Vector manipulation– Drug development – Drug resistance – Host genetic contribution– Rapid surveillance/diagnostic tools– Few new scientists entering the field

• BROADER SOCIETAL CHALLENGES– Universal Sanitation/Public Health– Adequate Housing– Adequate Food - nutrition– Available Health Care– Sustainability (Public/Private/Political Commitment)

– Few new public health officials entering the field