SAS 013 - Midterm 1

Antonie van Leeuwenhoek, microorganisms

The father of the microscope; called microoorganisms “animalcules.”

Factor V Leiden

Factor V Leiden is variant of the protein Factor V which is needed for blood clotting (coagulation).

People with this disease have blood that has an increased tendency to clot.

Johanna Westerdijk, Dutch elm Disease

Johanna was the first female professor in the Netherlands (1917), first described the Dutch elm Disease.

Caused by infection with a fungus called Ophiostoma ulmi.

Vector: elm bark beetle

Origin: Asia

The Dutch Disease, disease as a metaphor, disease-inspired cursing in dutch

Example of “disease” as a metaphor: something that is broken or in poor condition, such as an unhealthy marriage, a sick society, an ailing business.

Connection to cursing other people with disease.

Campaign to band “cancer” as a curse word.

Disease Taxonomy

A classification scheme for diseases

Tuberculous spondylitis, vertebral caries, Pott’s Disease are all the same disease

Pott’s Disease

Tuberculosis of bones and joints.

Chapter I: Certain infectious and parasitic diseases

Chapter XII: Diseases of the musculokeleteal system and connective tissues.

World Health Organization, ICD-10

WHO is in charge for ICD

ICD modification

Modified version of ICD-10 used in the US (CM-clinical modification)

How is ICD-10 used?, Medical Coding

Mortality Statistics, Public health/morbidity data, billing purposes

Medical coder: Extract billable information form the medical record

Classifying diseases by body systems

Muscular, Digestive, Nervous, Urinary, Reproductive, Circulatory, Hormonal, Lymphatic, Respiratory, Skeletal

Francis Collins, Cystic Fibrosis

One of the most common-life shortening inherited disease in the US.

Mutation in the CFTR gene

Overproduction of mucus clogs airways.

Chronic infection with slime-producing bacterium.

Francis Collins

Etiology

Means classifying diseases by CAUSE!

Infectious, Genetic, Environment

Christiaan Ejikman, Beriberi

In the 1990s, the Dutch colonies saw many cases of beriberi, a disease of the nervous system

Symptoms: Fatigue, Heart failure

Name from Singhalese

Hypothesis: caused by a bacterium

White rice is not toxic, but lacks VITAMIN B1

Nutritional deficiency diseases

Caused by a lack of essential nutrients in the diet.

Food insecurity, risk factor

Goiter

Iodine deficiency

Enlargement of the thyroid gland

Scurvy

Deficiency of vitamin C, common among sailors and pirates

Organizing diseases by mortality

By Deaths!

Illegal to Die of Old Age, 1951

Ebola Virus Diseases

2014-2016 outbreak in West Africa, largest since 1976

Excess Deaths

Deaths above what is historically expected

Case Fatality Rate (C.F. Ratio)

The proportion of people who die out of those who test positive.

How many of those people who get a disease also die from that disease?

Morbidity (prevalence and incidence)

Prevalence: Number of Cases per number of people in the population (All cases)

Incidence: Number of new cases over a defined period of time

National Notifiable Disease

COVID-19 is considered a national notifiable disease!

Covid Test - Antigen

Case classification: Probable

Rapid test, testing for the presence in the sample provided

Covid Test - Confirmed

PCR Test, detection of SARS-CoV-2 nucleic acid using a nucleiec acid amplification test (NAAT)

Covid Test - Suspect

Antibody test (serology) look. for a response of immune system to infection. Don’t detect Covid-19 virus directly, no diagnostic value.

Diagnostic Tests

Antigen, PCR

CURRENT INFECTION

Organizing Diseases by burden

DALY: disability adjusted life years

Disability weights factor into the calculation of DALY by representing the relative impact of a disease on an individual’s livelihood (0-1)

Low income vs. High income

A lot of information gets reduced to a single number

DALY = YLD + YLL

Defining Disease

Opposite of health.

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

Wikipedia: Disease often known to be a medical condition that is associated with specific symtomps and signs

Asymptomatic/Pre

Autism/Autism Rights Movement

Neural development disorder, impaired social interaction, and repetitive behavior

Normativists vs. naturalists

Normativists: Emphasize the undersirability of diseases and the harms and limitations they bring

“Illness and sickness”

Naturalists: Require the presence of biological dysfunction

“Disorder”

Debate on defining disease

What is disease?

All-inclusive definition

Aging

Aging is a disease the can be cured.

Aubrey de Grey: Accumulated in aged cells and tissues can be repaired using rejuvination biotech

Obesity

Excess adipose tissue

1. Hydrostatic weighing

2. Skinfold thickness

What factors?

Diet (not just a matter of choice, but also access)

Lifestyle (not always a matter of choice either)

Genetics: Common varian in the FTO gene, associated BMI and predisposes to childhood and adult obesity

Drugs, surgery, soda tax

Body Mass Index

Weight/Height²

(kg)/(m²)

Obesity: Gut microbiology

Human body with 10 trillion cells, carries about ten times that number of microorganism in the gut

Fecal transplantation

An obesity-associated gut microbiome with increased capacity for energy harvest

Disease Etymology

Etymology: the study of origins of words

Malaria - “bad air”

Lou Gehrig’s Disease

ALS is a disease the causes degeneration of the motor neurons of the central nervous system. Resulting in lsos of voluntary muscle control, and ultimately death.

Christmas disease

Named after Stephen Christmas

First known patient with haemophilia B

Deficient in Factor IX

Dependent on blood transfusion

Got infected with HIV, and died from AIDS

Huang Long Bing

A search engine named after disease

Typhoid Fever

Person named after a disease, Typhoid Mary

Alzheimer’s disease

Form of dementia was named after German psychiatrist who identified the first case of 1901.

Huntington’s Disease

Rare neurodegenerative disorder. Characterized by movement abnormalities, manifests itself between 35-44. Named after Long Island physician who described it in 1972.

Parkinson’s Disease

A degenerative disease was named after an English surgeon.

“An Essay on the Shaking Palsy”

Legionnaires’ Disease

First recognized outbreak occurred in 1976 at the Bellevue Stratford Hotel in Philadelphia, where members of a US military veterans association gather for the American Bicentennial.

Auto-brewery syndrome

Overgrowth of yeast in small intestine produces ethanol from sugary and starchy foods.

Ebola Virus (continued)

Discovered int 1976 in waht is now Democratic Republic of Congo

Virus had first surface called Yambuku, but was stigmatized.

Named after river that runs close to the village

From EHF to HVD, in reaction to the inaccurate perception that Ebola infection causes massive internal bleeding, contributing to masa and anxiety.

AIDS

Acquired Immune Deficiency Syndrome

GRID - Gay-Related Immune Deficiency

H1N1/09 Influenza

Swine Flu: genetic makeup revealed it is related to avian, human and swine viruses. Hurt pork producers

Mexican Flu: First known carrier was Mexican, hurt country’s economy

SARS outbreak

1. Report cases of any disease with potential for international spread

2. Raise awareness

3. Travel recommendations

4. internal collab

5. Strengthening of health system

6. Need existing interventions

Syphilis

Syphilis or the French Disease

Teponema Pallidum

Changing Disease Names: Wegener’s disease, Granulomatosis

Friedrech Wegener: Member of the Nazi Party before and during WWII.

Chronic Fatigue Syndrome (CFS)

Persistent fatigue unrelated to exertion, not relieved by rest.

Cause unknown

No lab tests available

Diagnosis of exlcusion: fatigue is common to other diseases.

Originally “myalgic encephalomyelitis” inflammation of the brain and psinal cord with muscle pain

Chronic Fatigue syndrome (1987)

Bad image, reserach suggests that a more medical sounding term renders this syndrome more serious

Infection

Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue.

Not equivalent to disease

Severity depends upon the ability of the pathogen to damage the host as well as the ability of the host to resist the pathogen.

Pathogenic microorganisms

Bacteria, Fungi, Viruses, Protists, Helminths (parasitic worms), priosn

Local/Systemic/Focal

Local: Infections confined to a small region of the body.

Systemic: Widespread infection in many systems of the body; often travels in the blood or lymph.

Focal: Infection that serves as a source of pathogens for infections at other sites in the body.

Primary vs. Secondary Infections

Primary: Initial infection within a given patient.

Secondary: Infections that follow a primary infection, often by opporutnisitc pathogens. Not normmally capable of causing disease in healthy host.

Acute/Chronic/Latent

Acute: Disease in which symtomps develop rapidly and that runs its course quickly

Chronic: Disease with symptoms that develop slowly and lasts a long time

Latent: Disease that appears a long time after infecton

Communicable/Contagious/Non-communicable

Communicable: Disease transmitted from one host to another

Contagious: Communicable disease that is easily spread.

Non-C

Tetanus

Wound infections by neurotoxin producing soil bacterium, Clostridium tetani

Mechanisms of disease transmission

Human to human

Animal to human

Via a vector

Fomites

Indirect contact, survival of influenza virus 1-2 days on door knob

Half-life

Time it takes for half of the virus particles to lose function.

Surface disinfectants and copper

Sprays and Wipes

Active ingredients: quaternary ammonium sodium hypochlorite, hydrogen peroxide

Soap and Hand Sanitizers

Alcohols in hand sanitizers denature the structure of proteins. Destroy the cell wall and membranes of bacteria cells, envelope of viruses. Less effective against non-enveloped viruses

Aerosols/Larger respiratory respiratory droplets

Early assumption of COVID-19 was large respiratory droplets, which are typical of airborne diseases

40,000 water droplets per sneeze, droplets remain airborne longer in dry air

Respiratory transmission is the dominant mode of covid (sneezing, coughin, spitting, speaking)

Social Distancing and Masks as means to reduce…

Masks reduce airborne transmission, protecting others and self

Cloth mask, surgical, n95

Small aerosol particle (1 micron)

PPE

Health workers at greater risk to contract the disease

Bodily fluids: blood, vomit, pee, poop sweat, semen, spit

Oral-fecal route of transmission

Fecal contamination of food/water, wash hands after using the restroom

Examples:

Typhoid fever, polio, foodborne illnesses

S-I-R Model

Susceptible: Not yet infected

Infected: Capable of spreading

Recovered: immune; no spreading

R₀ (R naught): Basic reproduction Number

If R naught less than 1, infection will not spread

If R naught greater than 2, epidemic will occur

Average R naught = 1.8

R naught is the average number of new infections that one infectious generates in an entirely suscpetible population, during the time that person is infectious

Different Methods for R Naught

Contact Tracing

Case Reporting

Ebola Outbreak 2014 R Naught

= 1.8 R_t < R₀

R_t

Effective reproductive number

To prevent an epidemic (1 - 1/R₀ × 100% of a population would need to be immune → Herd Immunity

Herd Immunity

A “herd” of recovered individuals protects susceptible individuals from infected ones, about breaking the chain of transmission.

Ways to achieve H.I.

Vaccination, natural infection

Vaccine Hesitancy, COVID

80% at least one dose, only 68% fully vaccinated

Simulation for spread of infection

Green: Healthy but susceptible (S)

Red: Sick and Infectious (I)

Grey: Recovered and immune (R)

Infectiousness

Chance that virus transmission will occur when an infected person and suscptible person meet

Chance-Recover

LIkelihood that an infection will end in recovery and not death

Duration

Time a person is infectious before recovery or death

Faroe Island Measles epidemic of 1871

At least 500,00 people required to sustain virus

Reintroduced in 1846

Individuals old enough to have experience the disease 65 years previously did not get sick → infection offers lifetime protection

Pathogen Attenuation/Endemic Disease

Neither humans nor the disease go extinct, maintained without outside input, depnds on new births

“Naive newborns”

Childhood Diseases

S → R by vaccination

Measles

Smallpox

Mumps

Diptheria

Whooping Cough

Zoonotic Diseases

Animal to human

Rabies

Virus; animal bite

Toxoplasmosis

1/3 of the world’s human population is estimated to carry a Toxoplasma infection

Most people infected never develop signs

however, infants born from infected mothers with weakened immune system and can develop complications

Felines are primary hosts → Kitty Litter Box, Undercooked meat

T. gondii needs cats to reproduce in

When it finds itself in a rodent, it will chance host’s behavior to maximize its return to cats (manipulation hypothesis)

Ebola - Zoonotic

Bats and other wild animals carry Ebola Virus

Bushmeat

Bushmeat as the primary protein source

Cheaper than other sources of protein

Cultural significane

Introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals

Bats as a natural reservoirs of viruses, Spillover zoonoses

Bats are a natural reservoirs to many viruses, some of which have led to disease outbreaks in animals and humans

Sac-winged bats → Ebola

Horsehoe bats → Coronaviruses

Market in Wuhan as the epicenter of the Covid-19 pandemic

Cluster of earliest cases center around the Huanan market in Wuhan, no bats sold at the market

Cluester of Covid positive environmental samples, spatially associated with vendors selling live mammals

2 distinct lineages

Suggesting 2 cross-species sepearte transmission events into humans, one became now what is the pandemic

“Lab Leak Theory”

Wuhan Institute of Virology

Conducting research on SARS-like bat coronaviruses since 2005

Accidental or intentional?

Malaria

Vector-borne disease

Transmitted by mosquitoes (genus Anopheles)

ONLY FEMALE

Caused by protists of the Plasmodium genus (e.g. P falciparum)

Found in tropical, sub-tropical areas

241 million cases, 627,000 cases in 2020

96% deaths in Africa

Once an endmic in southern US

Eradicated by 1951

Life Cycle of Plasmodium

Mosquito ingests the parasite by feeding on blood from infected human carrier

Parasites reproduce sexually in the midgut of the mosquito and migrate to salivary glands

Parasite is transmitted when infected mosquito takes a blood meal

Within 30 minutes, parasite reach and infect liver cells, 5-16 days multiply insides (no symptoms)

Parasites re-enter blood stream, infect red blood cells and multiply

Infected blood cells burst, releasing new paraistes, which infect more blood cells Some develop into gametocytes

Vector Control

It was thought that malaria came from breathing in the rotting stench of marshes and swamps

Draining swamps releasing fish

Paris Green (Copper (II) Acetoarsenite)

Kerosene oil

DDT

Dicholor-Diphenyl-Tricholoethane

Very effective

Affects wildlife, causes cancer, endocrine dsiruptor

Banned in the US (1972)

Silent Spring 1962, Rachel Carson

Still being used where disease is an endemic, applied in walls of houses

Con DDT: Greenpeace, WWF

Netting

Most feeding occurs at night, bed nets responsible of 68% of 663 million preented cases of malaria in Africa 2000-2015, compared to 10% by insectides

Vector control

Genetically modified male mosquitoes engineered to shrink local populations of Aedes aegypti

Protection from dengue, Zika, yellow fever, and other vector-borne diseases