- comes from the latin term plaga (sudden stroke)

-any disease of wide prelalence or of excessive mortality

- mechanisms resulting in development of disease

-> physiological

-> biochemical

- anything abnormal that indicates disease

- ex. rash

- objective

- can be discovered during an examination

- any departure from normal structure, function, or sensation

- ex. itchiness, soreness

- subjective (can't measure)

- experienced by the patient

- community is resistant to the invasion/spread of disease

- they're exposed to the pathogen but they don't get it

- disease introduced to a population that has no immunity

- either they were never exposed or the resistance is gone

- an organism that lives in other organisms

- causes disease in host

- macro/micro pathogens

- soil

- water

-animals

**zoonosis: a disease that can be transferred from non-human to human

- the carriers, gets the diseasee through the contact of another organism

- ex. mosquitoes, fleas, body lice

- airborne

- fecal-oral

-skin

- placenta

- epithelium

-> skin

-> respitory tract

- endothelium

-> gastro-intestinal tract

-> uro-genital tract

Depends on:

host properties:

-> immune function

-> nutrition

-> other infections

-> age at exposure

pathogen properties:

-> virulence

-> number of pathogens

-> route of infection

- used to describe the process of disease spread

- predicts patterns of disease outbreaks and spreads

- patterns vary with population size

- susceptibility

- infectives

- basic reproductive number (Ro) of disease

- contact rate (# of close personal encounters)

- based on the number of infections caused by a single infected individual

- calculated at the start of an endemic

- can implicate public health measures

- longer infectious preiods

- increase in the number of contacts with susceptible individuals

- increase in population size

- disease spreads faster

- higher proportion of hosts infected

- higherr disease burden

- estimates the risk of an endemic

- compare transmisibility of a new disease with other will known diseases

- informs on the efficiency of health measures

- the number of close personal encounters per unit time

- each interaction has the potential for pathogen transmission

- culturally influenced

- ex. Sarawaka, Malaysia

-> dif types of housing

-> some use long houses and others use single family dwellings

-> people in long houses have an increased chance of getting TB

- regular series of outbreaks

- population: 300,000-500,000

- regular patterns of outbreaks

- discontinuous presence

- not enough suseptible people

- population: 300,000-10,000

- outbreaks at irregular intervals

- population: <10,000

Caused by:

- climate change at the end of the Pleistocene

- glaciers receeded and climate more mild and dry

- many larger animals extinct

Results:

- became farmers

- increase in population, became more concentrated

- greater increase in the potenital for infectious diseases to spread

- reduced variability in animal and crops

- used human waste and animal feces as fertilizer

- caused changes in the environment

- decline in sanitary conditions

Sedentism

- living in one place year round

- have active interactions with the environment

- can be seen in the arch record:

-> thickness of arch deposits

-> presence of human commensal organisms

- Hungarian obstetrician

- puerperal fever (women dying during child birth)

- casue:

-> not miasma

-> should wash hands

-> dreath rates from child birth dropped

- prevent introduction of disease into wound or person

- maintain sterile environment

- strong opposition

-ex. hand washing

- kill infections already in the body

- Joseph Lister:

-> shouldn't just do hand washing

-> carbolic acid on patient's wounds

- reducing the perception of pain

- the lost of consciousness

- people objected to this, pain is good

- noise distraction, hypnosis

- restraints

- herbal remedies (opium, nightshade, hemlock)

- first id: 1772

- routine use: 1866

- laughing gas parties

- doesn't last very long

- not as effective as ether

- first id: 1818

- routine use: 1846

- ether parties

a seeper anesthesia than n20

- explosive, bad for respiratory system

- first id: 1831

- routine use: 1847

-  chloroform parties

higher death rate than n2o

- coal tar used to make dyes

- dyes used as drugs

- ex. salvarsan: first effective treatment for syphilis

- enhanced trasmission of disease

-> water, air

-> dwelling construction

->vectors

-> proximity to domesticated animals

- parasites with long-lived transmission stages

- person-to-person contact

- disease endemic

Nile Valley

- has annual flooding

- nutrients for soil, good for crops

- have annual snails

- important for washing, drinking, irregation

-20th century:built dams

- improved habitat for snails, now year round

- there's less nutrients for soil, need fertilizers

- increases disease

Plague of Athens

(Peloonnesian War)

- war between Athens and Spartans

- Athenians wanted total power

- Athens: strength on water, Spartans: strength on land

- Athenians surrounded by Spartans

- declining sanitary conditions, crowding, low food

-orchards and vines destroyed

-consequences from disease:

- death of 30% of Athenians

- lack of regard for the law (theft, partying)

- dishonourable behaviour

- fear of caring for the sick

-religious upheveal (gods angery at athens, sided with spartans)

- the arrival of malaria to europe

- transmitted by mosquitoes

- mosquitoes survived because:

- deforestation  

- wintered in barns and houses

- marshes replaced harbour, created habitat

- 2 week incubation in liver

- into red blood cells

- RBC rupture

- high fever, chills, headache, muscle pains

- enlarged spleen

- enlarged liver

- moderate anemia

Typhoid

- samonella enteric

- discovered in 1880s

- transmitted: fecal-oral

- causes: nausea, vomitting, fever, diarrhea

- symptoms: appear 12-72hours after infection

-can last up to 7 days

- high mortality rate

- morbillivirus

- transmitted: airbourne route

- STAGE 1: (day 10-12)

->cough, runny nose, red/watery eyes

-> lasts 3-7 days

-> infective up to 4 days before rash

-STAGE 2: (day 13-19)

->rash, fever

-> infective first 4 days of rash

-> potential complications

-has 10% mortality

-schistosomiasis

- rash (at entry site)

- fever, diarrhea, coughing, swollen lymph nodes

- liver and spleen enlargement

- blood in urine (s.haematobium)

- blood in feces (s.mansoni)