Public Health and infectious disease prevention

Carlos Amade, MD

Content

• History of public health• Social Medicine• Community health and

community healt• Achievements of public health• Challenges of public health• Infectious disease prevention • Bibliography

Health is central to our lives

Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

WHO, June 1946

Health belief: Amulet ‘protection’ against cholera (France)

Conception of public health involving, politics, medical and social sciences "Die Medicin ist eine sociale Wissenschaft“ (Medicine is a social science and politics is nothing else but medicine on a large scale). Rudolf Vichow, Berlin mid 1800s

The Health Crisis: Origins Of Modern Public Health

Rapid concentrations of population which overwhelm water supply, sanitation and housing

Civic protest against water pollution (England 1830s)

Environmental, health and equity issues

World’s first major public health legislation: 1848 (Edwin Chadwick, England)

New industrial way of life, dangerous work, transport, pollution, accidents, food adulteration, etc.

-Migration and break up of social networks-State modernization held back by elites, yet emergence of civil society

What is public health?

• Action by society to protect and promote the health of everyone

• Involves science, evidence, art, politics and imagination

• Requires partnerships and the involvement of the population

• Requires knowledge, skills, motivation and commitment

• Requires leadership and co-operation, often across border

Concept of Public Health“…the science and art of

preventing disease, prolonging life, and promoting physical health and efficiency, through organized community efforts, for the sanitation of environment, the control of community infections, the education of the individual in the principles of personal hygiene, the organization of medical and nursing service for early detection and preventive treatment of disease, and development of the social machinery which will ensure to every individual in the community a standard of living adequate for the maintenance of health”

Winslow

Summarized concept of P.H.

The science and art of preventing disease, promoting health and prolonging life through organized efforts of society.

Elements in the concept

• Collective responsibility• Prime role of the state in promoting and

protecting the people health• Partnership with the population served• Emphasis on prevention• Recognizing socioeconomic determinants• Identifying and dealing with risk factors• Multidisciplinary basis of action

Early names of Public Health

• Preventive medicine• Social medicine• Community medicine• Community health

Now they are dimensions of Public Health

The dimensions of Public Health

Public Health

Social Medicine

Preventive Medicine

Community Medicine

Community Health

Preventive medicine

• Prevention is better than cure• Encompasses both the care of

individual patients, and public health practice

• Initially only for healthy people (vaccination, nutrition,…)

• Then early diagnosis• And now includes treatment of

sick people

Four (early three) levels of prevention

Social Medicine• The poor die young

Social Medicine• Social status linked to health of individuals

and community

• “The existing inequality in the health status of people between developed and developing countries as well as within countries is politically, socially and economically unacceptable and is, therefore, of common concern of all people”. Alma Ata, 1978

Rainbow of health determinants

• Source: Dahlgren G and Whitehead M (1991) Policies and strategies to promote social equity in health. Stockholm, Institute for Futures Studies

Assumptions of Social Medicine

Health

birthright

state (country)

development

educationsocial factors

begins at home

poverty

Community HealthServices that aim to protect the

community

Sanitation

Vector control

Health education

Water supply,….

Community Medicine

• Health Services provided at community level

Now it is Primary Health Care

Modern Public Health

• Multidisciplinary• Multisectorial• Evidence-based• Equity oriented

Public Health Clinical Medicine

Focus Populations Individuals

Ethics Public service Personal

Emphasis Disease prevention and health promotion for the whole community

Disease diagnosis, treatment, and care for the individual patient

Paradigm Interventions aimed at the environment, human behavior and lifestyle, medical care

Emphasis on medical care

concerns major threats to the health of populations;

Biological sciences central, stimulated by needs of patient

What has public health achieved?

Ten Great Public Health Achievements -- United States, 1900-1999 (according to US CDC)

• Vaccination• Motor-vehicle safety• Safer workplaces• Control of infectious diseases• Decline in deaths from coronary heart disease and

stroke• Safer and healthier foods• Healthier mothers and babies• Family planning• Fluoridation of drinking water• Recognition of tobacco use as a health hazard

Great Public Health Achievements in Europe 1900-2000?

• Extended life largely free of disease – healthier children, healthier old age

• Family planning and reproductive rights for women

• Cleaner air in cities• Better, less crowded housing• Safer workplaces and work processes• Reduction of infectious diseases• Safer and healthier range of foods•…. ?

Africa???

Challenges of public health

• Resurgent infectious diseases and new infectious diseases

• New avoidable chronic diseases (NCDs) • Impact of globalization, industrialization,

urbanization and population change on determinants of health and ecology.

• Inequality and growth of socially excluded groups

• Role of anti-health forces – tobacco, alcohol, processed food, ‘culture industry’

• Public policy - changes in the roles of governments in relation to population health and health care.

Infectious Disease and public health:

Classification of Diseases & Health Problems

Organ or Organ System– i.e., heart disease, kidney disease, respiratory

infection

Causative Agent– Biological Agents– Chemical Agents– Physical Agents

Communicable vs Non communicable

Acute vs Chronic– Peak symptoms within 3 months (acute) or

longer than 3 months (chronic)

Classification of Infectious Disease

• By duration– Acute – develops and runs its course quickly.– Chronic – develops more slowly and is usually

less severe, but may persist for a long, indefinite period of time.

– Latent – characterized by periods of no symptoms between outbreaks of illness.

• By location– Local – confined to a specific area of the body.– Systemic – a generalized illness that infects

most of the body with pathogens distributed widely in tissues.

• By timing– Primary – initial infection in a previously

healthy person.– Secondary – infection that occurs in a person

weakened by a primary infection

Infectious (communicable) disease

Is caused by transmission of a specific pathogenic agent to a susceptible host.

Robin Cochran-Dirksen (Many slides from BioEdOnline Baylor Christine Herrmann

PhD)

Infectious Diseases - Definitions

• Disease – a pathological condition of body parts or tissues characterized by an identifiable group of signs and symptoms.

• Infectious disease – disease caused by an infectious agent such as a bacterium, virus, protozoan, or fungus that can be passed on to others.

• Infection – occurs when an infectious agent enters the body and begins to reproduce; may or may not lead to disease.

• Pathogen – an infectious agent that causes disease.

• Host – an organism infected by another organism.

• Virulence – the relative ability of an agent to cause rapid and severe disease in a host.

Robin Cochran-Dirksen (Many slides from BioEdOnline Baylor Christine Herrmann

PhD)

Infectious Disease Agents

• Most infectious agents that cause disease are microscopic in size and thus, are called microbes or microorganisms.

• Different groups of agents that cause disease are:– Bacteria– Viruses– Protozoa (Protists)– Fungi– Helminths

Infections do not arise in a vacuum

Factors That May Increase Risk of Human Disease

Host Factors Agent Factors Environment factors

Host Characteristics Types of Agents and Examples Environmental FactorsAge Biologic Temperature

Sex Bacteria, viruses Humidity

Race Chemical Altitude

Religion Poison, alcohol, smoke Crowding

Customs Physical Housing

Occupation Trauma, radiation, fire Neighborhood

Genetic profile Nutritional Water

Marital status Lack, excess Milk

Family background Food

Previous diseases Radiation

Immune status Air pollution

Noise

Modes of disease transmission

• Direct– Person-to-person

contact• Indirect– Common vehicle• (1) Single exposure• (2) Multiple exposures• (3) Continuous exposure

– Vector, vehicle, air

Transmission

Contagious diseases

• Without an intervening vector or vehicle

Robin Cochran-Dirksen (Many slides from BioEdOnline Baylor Christine Herrmann PhD)

Phases of Infectious Disease

• Incubation period – time between infection and the appearance of signs and symptoms.

• Prodromal phase – mild, nonspecific symptoms that signal onset of some diseases.

• Clinical phase – a person experiences typical signs and symptoms of disease.

• Decline phase - subsidence of symptoms.• Recovery phase – symptoms have

disappeared, tissues heal, and the body regains strength.

Robin Cochran-Dirksen (Many slides from BioEdOnline Baylor Christine Herrmann PhD)

Related Terms• Endemic/Enzootic: The constant presence of a

disease or infectious agent within a given geographic area.

• Epidemic/Epizootic: The occurrence in an area of a disease or illness in excess of what may be expected on the basis of past experience for a given population (in the case of a new disease, any occurrence may be considered "epidemic").

• Pandemic/Panzootic: A worldwide epidemic affecting an exceptionally high proportion of the global population.

The burden of communicable disease

• Communicable diseases account for 14.2 million deaths each year

• Most in low-income settings Acute respiratory infections (3.76 million) HIV/AIDS (2.8 million) Diarrhoeal diseases (1.7 million) Tuberculosis (1.6 million) Malaria (1 million) Measles (0.8 million)

The burden of communicable disease

Infectious disease are threats to human security and health systems

Pose an acute threat to individual health

Have the potential to threaten collective human Security

Low-income countries continue to deal with the problems of communicable diseases, deaths due to chronic diseases are rapidly increasing, especially in urban settings

The challenge of infectious diseases

• 20 well-known diseases - TB, malaria, and cholera - have further spread since 1973, often in more virulent and drug-resistant forms.

• Plus at least 30 previously unknown disease agents identified since 1973, including HIV, Ebola, hepatitis C, and Nipah virus, for which no cures are available.

• HIV/AIDS and TB likely to account for the overwhelming majority of deaths from infectious diseases in developing countries by 2020.

HIV/AIDS• 40 million people in the world infected with

HIV.

• In 2011, 4 million became infected with HIV, and 3 million died of the disease.

• That is 8,000 deaths every day.

• 6 million are in immediate need of AIDS treatment.

HIV, 2012 (WHO)

HIV, 2012 (WHO)

Malaria protected population

Malaria and drug resistance

Infectious disease prevention and control• Prevention– Includes individual, clinical, or personal

health services such as immunizations, screening for high blood pressure and follow-up services, or the use of Pap smears to detect the precursors to cancer of the cervix.

• Protection– Includes the activities of organizations,

both public and private, to reduce exposure to hazards such as polluted water, contaminated food, traffic accidents, mosquitoes, or use of electric saws without safety devices.

Primary Prevention of communicable diseases

Community actions

• Chlorination of the water supply,

• Inspection of restaurants,

• Immunization programs that reach all citizens,

• Maintenance of a well-functioning sewer system,

• Proper disposal of solid waste

• Control of vectors and rodents.

Personal/Individual action

• Hand washing, • Proper cooking of foods,• Adequate clothing and

housing,• Use of condoms, • Obtaining all of the

available immunizations against specific diseases

Secondary Prevention of communicable diseases

Community effort • Includes measures taken to

control or limit the extend of a disease outbreak

Maintaining records of cases and compliance with regulations requiring the reporting of notifiable diseases

Investigating cases and contacts, those who may have become infected through contact with cases

Individual effort

• Self-diagnosis and self-treatment with nonprescription medications or home remedies

• Diagnosis and treatment with an antibiotic or other physician-prescribed medicine

Occasionally, secondary disease control measures may include isolation or quarantime

Further measures may include disinfection and mass treatment with antibiotics

Tertiary Prevention of communicable diseases

• Physical therapy• In some cases, such as paralytic

polio, return to normal activity may not be possible, even with extensive physical therapy• At the community level, proper

removal of infected items such as clothing, disinfection, and burial of the dead.• Tertiary prevention may also involve

the reapplication of primary and secondary measures to prevent further cases

Herd Immunity

• Resistance of a group of people to an attack by a disease to which a large proportion of the members of the group are immune.

Herd immunity

Bibliography

• Bonita Epidemiology• Gordis Epidemiology• Harvard University, School of Public Health

(Online)• John Hopkins University (Online)• Short textbook of Public Health• WHO

Thank you