Exam 3 for Galloway

Types of disease

• infectious

• non-infectious

Infectious diseases

Dz caused by different classes of pathogenic organisms commonly called germs

• Dz producing “germ”/agent such as virus or bacteria

Non-infectious

any Dz not caused by a pathogen (e.g., asthma, CVD, obesity)

Infectious diseases are a leading cause of death worldwide

particularly in low-income countries, especially in young children

>650K deaths associated with

respiratory diseases from seasonal influenza

>1.2 million deaths from

diarrheal disease; >390K were among children under 5 years in 2021

>136K deaths from

measles in 2022

U.S. - although we have “eliminated” or “eradicated” some

infectious Dz still a major PH problem (e.g., pneumonia, influenza, HIV, STI/STDs, TB)

• “emerging” infectious diseases; many from animals (zoonotic)

• antimicrobial resistance

• addressing the complexities involved is not easy

Zoonotic

diseases cause by infectious agents that can be trasmitted between (or are shared by) animals and humans

One Health

“achieving optimal health outcomes recognizing the interconnection between people, animals, plants, and their shared environment”

More types of disease

• communicable

• contagious disease

Communicable

an infectious disease that may be passed from individual to individual

While they are often used synonymously

the terms infectious disease and communicable disease do not have the same meaning

A communicable disease is an infectious disease that

is easily spread from one species to another

All communicable diseases are infectious diseases, but

not all infectious diseases are communicable (e.g., infected cut, tetanus, Lyme dz)

Contagious disease

is a very communicable disease, i.e., an infectious disease that very readily spreads from person to person

Types of agents

1. bacteria

2. viruses

3. fungi

4. protozoa

5. helminths

1. Bacteria

one-cell microorganism that multiply quickly & may releases chemicals which can make you sick (e.g., TB, tetanus, cholera, whooping cough)

2. Viruses

capsules that contain genetic material & use your own cells to multiply (e.g., flu, HIV)

3. Fungi

primitive vegetable, like mushrooms, mold, yeasts (e.g., Histoplasmosis, athlete’s foot)

4. Protozoa

one-celled animals that use other living things for food and a place to live (e.g., malaria, toxoplasmosis)

5. Helminths

parasitic worms that cause disease and illness in humans (e.g., tapeworm, pinworm, and roundworm)

Host (reservoirs)

• non-vector

• vector

Non-vector host

• humans

• other vertebrates

• birds, bats

Vector host

• asymptomatic carriers of pathogens

  • mosquitoes

  • ticks, flies

Routes of transmission

• eyes

• mouth

• nose

• skin

• digestive tract

• genitals

• urinary tract

direct or indirect

Direct routes of transmission

• skin-skin

  • Herpes type 1

• mucous-mucous

  • STIs

• across placenta

  • Rubella; HIV

• through breast milk

  • HIV

• sneeze-cough/aerosolized from person to person

  • Influenza, TB

Indirect routes of transmission

• food-borne

  • Salmonella

• Water-borne

  • Cholera

• vector-borne

  • Malaria

• air-borne/aerosolized from person to object

  • Chickenpox, colds

Environmental factors

• land use (e.g., (deforestation, reforestation, outdoor activities)

• infrastructure

  • air filtration/conditioning; screens on windows; access to clean water

• changes in food production & handling

  • use of antibiotics in animal farming

• increased use of immunosuppressives/antibiotics

• global air travel

• ownership of (exotic) pets/interaction with animals

• natural disasters

The “Epi” Triad (triangle)

—-—Agent——

——Disease——

Host ——— Environment

Dynamic interaction

The “Epi” Triad; Host factors

• age

• sex

• genotype

• behavior

• nutritional status

• health status

The “Epi” Triad; Agent factors

• infectivity

• pathogenicity

• virulence

• immunogenicity

• antigenic stability

• survival

The “Epi” Triad; Environment factors

• weather

• housing

• geography

• occupational setting

• air/water quality

• food

Why can some be “eradicated” and not others

• type of reservoir

• ability to live outside of humans

• “carrier state” - e.g., host shows symptoms

• Dz produces long-term immunity

• vaccine available to produce (long-term) immunity

• herd immunity acheivable?

• ease of Dz to change

  • example: smallpox/polio/measles vs. HIV

PH (population) “tools” for communicable disease

• control measures

• barrier protection

• immunizations

• screening & treatment

• public health campaigns

Personal prevention tips for communicable Dz

• PPE (personal protective equipment)

• handwashing

Control measures

• water treatment

• vector control

• rodent reduction

Barrier protection

• isolation

• quaratine

Immunizations

introduces antibodies (injection, nasal) to stimulate immune system to produce own antibodies

Vaccine types

• live-attenuated vaccines (MMR, chick pox)

• inactivated (dead) vaccines (flu, polio)

• subunit, recombinant, polysaccharide, and conjugate vaccines (HPV, whooping cough)

• toxoid vaccines (diptheria, tetanus)