Basic Concepts in Public Health and Tropical Medicine
[Infectious Diseases and Public Health 101]
(mainly in relationship to parasitic diseases)
Daniel G. Colley
Medical Parasitology; CBIO 4500/6500
24 January, 2008
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;..)
Ebola; WNV; SARS; Lyme; Hanta; Cryptosp; Cyclospora; E. coli 0157/H7
Nosocomial Infections; Community Acquired MRSA
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 9/12 9/18 9/23 • U.S. Cases 1 6,674 12,604 (727 deaths)
25% of Civilian Population Infected 4/100 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
Mortality Rate per 100,000 1000 800
1957
20th Century Flu Pandemics
1918 > 500,000 U.S. deaths > 20,000,000 deaths worldwide (H1N1) ~ 70,000 U.S. deaths ~ 1,000,000 – 4,000,000 worldwide (H2N2)
600 400 200 0 1900
1968 ~ 33,000 U.S. deaths ~ 750,000 deaths worldwide (H3N2) --------------------------------------------------200? ~ ?????? (H5N1??)
1920
1940 Year
1960
1980
January 21, 2008
Spreading still, but no pandemic…..yet…. “Vigilance is the price of freedom”
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
Chloroquine 16 years Fansidar 6 years
Mefloquine 4 years
Atovaquone 6 months
1940
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 Cryptosporidiosis Cyclosporiasis African Trypanosomiasis Drug-resistant Malaria Focally there are many others (even schistosomiasis…)
Major Factors Contributing to the Emergence of Infectious Diseases
1. 2. 3. 4. 5. 6. Human demographics and behavior Technology and industry Economic development and land use International travel and commerce Microbial adaptation and change Breakdown of public health measures
Institute of Medicine Report 1992
Moving on to:
Public Health
• The concept of Public Health differs from the concept of individual medical care, and the skills are very often different • 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, but rather populations at risk
[Artemisinin combination therapy to Rx or to thwart malarial drug resistance?] (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/disease (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/run implementation programs 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
• Impair Development/Quality of Life • Major Killers – Lymphatic filariasis - 120M – Malaria; ~400M – Chagas’ disease; – Geohelminths - 2B – Schistosomiasis – 200M 18M – Onchocerciasis – 18M – African – Cysticercosis ? 50M tapeworm Trypanosomes; – Waterborne/Foodborne ~0.5M protozoans – 1.5B – Visceral – Cutaneous Leishmaniasis; 8M Leishmaniasis; – Guinea worm – 4M < 15K ~4M
What does it take for 1 million people to die a year ???
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)
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
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 • ~5000 die per day • ~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
– Major Impediment to Economic Growth and Development, as well as health
A few thoughts on the impact of global infectious diseases
1. In 2000 about 11 million children died before their 5th birthday -- more than 99% of these 11 million died in low- to middle-income countries – most from infectious diseases 2. The household costs due to malaria are often 5%-10% of the annual income, and when seen based on income level, it soared to 30% of the income of very poor families, i.e., these costs are very regressive – the poorer you are, the worse they hit you
These and other facts like them have caused global economists and international development officials to see the relationships between POVERTY, HEALTH & DEVELOPMENT in a new light
Development Health
Health Development
Improved health contributes to economic growth in four ways
1. Reduces production losses caused by worker illness 2. Permits or improves uses of natural resources inaccessible due to disease 3. Increases enrollment in school and allows children to learn – Future… 4. Frees up resources spent on treating illness for alternative uses
The World Bank World Development Report, Investing in Health,1993; [This publication represents a major change in thinking on “development”]
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 parasitoses
Naeglaria is not on the list (small numbers), but perceptions can control what gets considered “public health”……
Worms are not Protozoans Protozoans 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. Morbidity
These 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. Based on the LIFE CYCLE • 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
Infectious diseases
• • • • Some are global Some are geographically focal Some are economically important Some are socially important
Need to consider all these aspects -not just assemble the right tools…….
Need to think of the conceptual differences between medical care and public health, and how the two should interact in a complementary way
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; 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]
Piloted now
• Schistosomiasis – Control • Soil-transmitted helminths – Control
Possibles
• Taeniasis & Cysticercosis – Eradication • Echinococcosis; Elimination • African Trypanosomiasis; Control
•
Other infections:
Eradication Polio (virus) Measles (virus) Elimination (complete, or as “a public health problem”) Trachoma (bacterium) Leprosy (bacterium)
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)
[Down from 20 to 5 countries]
Niger (11), Nigeria (73), Mali (313), Ghana (3,358), Sudan (6,298)
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 effort Drug resistance – the threat of any drug- based anti-infectious disease program - especially with a single drug Monitoring ?? 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