Disease and Society Midterm 1

Antonie van Leeuwenhoek

He was Dutch and became a scientist, Father of Microbiology. Invention and advancement of the microscope (improved it by creating a lens that could magnify more). He made the discovery of microorganisms, first person to observe them. He had the Germ theory of disease, medical microbiology, and the understanding that microorganisms could be linked to infection and disease.

Johanna Westerdijk

First female professor in the Netherlands (1917), plant pathology and mycology. Studying the disease in trees, the dutch elm disease. The dutch elm disease is a fungal infection and she led the first major research program, developed antifungal treatments

Francis Collins

Leadership of the Human Genome Project, mapped the entire human genome, helped research for genetic diseases like cystic fibrosis. Discovered genes responsible for disorders like Cystic fibrosis and Huntington's disease. Director of the National Institutes of Health. Helped identify the CFTR gene for cystic fibrosis

Christiaan Eijkman

A Dutch physician discovered the cause of Beriberi, he was studying it and he observed that chickens fed polished (white) rice developed symptoms similar to beriberi while those fed unpolished (brown) rice did not. Conclusion: Beriberi was not caused by infection but by dietary deficiency. Improved the importance of certain nutrients in preventing disease. Showed that it was a severe vitamin B1 deficiency. He won a nobel prize in physiology or medicine in 1929

Rachel Carson

American marine biologist, writer, and environmentalist. Made the book Silent Spring which sparked the modern environmental movement. Exposed the dangers of widespread pesticide use, especially DDT. Showed how the chemicals used in agriculture and mosquito control contaminated water, soil, and wildlife enter the food. Also warned about the long-term health effects. Inspired environmental health policies and safer vector control.

Tu Youyou

Some people question the decision to award the Nobel prize to Chinese scientist Tu Youyou for her discovery of artemisinin because she did not make this discovery on her own, but as part of a collective. Discovered artemininin, a powerful anti-malarial compound, first Chinese woman to win a Nobel Prize in Physiology or Medicine. Revolutionized treatment of malaria, especially drug-resistant forms, saved millions of lives, particularly in developing countries.

Animalcules

It was used to describe tiny, microorganisms, this was said by Antonie van Leeuwenhoek when he looked at them through the microscope, examples of them are bacteria and sperm cells

Factor V. Leiden

Variant of the Protein Factor V which is needed for blood clotting (coagulation). It is named after the city of Leiden (the Netherlands), where it was first identified in 1994, people with Factor V Leiden have blood that has an increased tendency to clot. It is most common cause of hereditary thrombophilia in the US

The Dutch Disease

1960s discovery of large natural gas deposits in the North Sea. exports caused an increase in wealth from foreign currency inflow. The Dutch guide became stronger. Exports of all non-gas products less competitive on the world market, aka as the resource curse or paradox of plenty

Disease-inspired cursing in Dutch

The Dutch use diseases and insults. Disease like typhus, plague, and cancer were common in the Netherlands, the disease caused immense pain and suffering, and death, expressing anger. Example is using cancer as a way on insult

Disease as a metaphor:

Something that is broken or in poor condition, such as an unhealthy marriage, a sick society, an ailing business, or the dutch disease is an example of this

Disease taxonomy

A classification scheme for diseases, this includes the ICD

World Health Organization

Specialized agency of the United Nations responsible for international public health, promoting health and to keep the world safe. Provides leadership on global health matters, sets international health standards and guidelines. Disease prevention, control, and response. Coordinates responses to health emergencies like Covid-19. Fighting the infectious diseases like malaria

International Classification of Diseases (ICD)

It is used to facilitate communication like police scanner codes. It is a globally used system for coding and classifying diseases, health conditions, and related problems. Developed and maintained by the World Health Organization. Gives a standardized framework to record and report diseases across countries. Standardizes diagnosis coding, tracks diseases, global health monitoring, used for billing, insurance claims, and medical records. There are examples for almost any type of disease and condition (A18.0 = tuberculosis of bones and joints). It can be used as a morality statistics classification system for causes of death. Public health and morbidity = how they spread, where they are prevalent, and to budget programs

ICD-Clinical Modification

Modified version of the ICD, adapted specifically for use in clinical settings, primarily in the US, more detailed and specific coding for diagnoses and procedures than the ICD. greater specificity for billing, epidemiology, and research. Helps with hospital records, insurance claims, and healthcare data systems, examples include K71.51 which is toxic liver disease with chronic active hepatitis with ascites

Medical coding

Process of translating healthcare diagnoses, procedures, medical services, and equipment into standardized codes. Used to accurately document patients, facilitate billing and insurance claims, track health statistics and research, Example = type 2 diabetes mellitus without complications = ICD-10 code: E11:9

Body systems

Muscular (all the muscles, including skeletal, smooth, and cardiac), digestive (breaking down food, absorbing nutrients, and eliminating waste), nervous (body’s communication network that controls and coordinates all voluntary and involuntary actions), urinary (removing waste products and excess fluids from the blood, regulating blood pressure), reproductive (responsible for producing offspring), circulatory (transporting blood, oxygen, nutrients, hormones, and waste products throughout the body), hormonal (gland and organs that produce and release hormones - chemical messengers that regulate body functions), lymphatic (circulatory and immune systems, helps fight infections, remove waste, and maintain fluid balance), respiratory (responsible for breathing), skeletal (framework of bones and connective tissues that provides structure, support, movement, and protection for internal organs)

Etiology

Cause or origin of a disease or condition

Disease etiology 

• Infectious: bacterium, fungus, virus, protist, helminth, these can lead to disease like cholera, athlete’s foot, ebola virus disease, malaria, and ancylostomiasis

• Genetic: autosomal, sex-linked, dominant, and recessive. This is hereditary and passed on from generations, examples include cystic fibrosis, huntingtons disease, alzheimers. 

• Environmental: too much of a bad thing like alcohol can lead to diseases and too much of a good thing like Iodine can lead to diseases.

Nutritional deficiency diseases

Caused by a lack of essential nutrients in the diet, this is seen more in the past because foods are not genetically modified to have the essential nutrients needed. Examples equal = goiter. It is not only a thing of the past but it is also where there are food insecurities.

Food insecurity

Lack of consistent access to enough food for an active healthy life

Risk factor

Something that increases the chance of developing a disease

Anaemia

a condition in which the number of red blood cells or the haemoglobin concentration within them is lower than normal

Excess deaths

The number of deaths that occur beyond what is normally expected during a specific time period in a given population. Formula = excess deaths = observed deaths - expected deaths. This is important because it can track the total impact of health emergencies like COVID-19.

Case fatality rate

The proportion of people who die out of those who test positive. The proportion of people who die from a specific disease among all individuals diagnosed with that disease over a certain period of time. CFR = (number of deaths from the disease / number of confirmed cases) x 100. It can overestimate the fatality if many mild or undiagnosed cases exist because it only has confirmed cases. How many of those people who get a disease also die from that disease

Mortality rate

Measures deaths in the entire population

Morbidity (disease prevalence and incidence)

The prevalence (all cases) or incidence (new cases) of a disease in a population. Prevalence = what is the number of disease individuals in a population. Incidence = how many new cases per day/week/year

National notifiable disease

A disease or condition that healthcare providers are legally required to report to national health authorities like the CDC, example includes COVID

Covid tests (antigen, nucleic acid, PCR, antibody diagnostic)

A confirmed test is seen with the PCR/Nucleic acid test which is the detection of SARS-CoV-2 nucleic acids using a molecular amplification test. A probable test is the detection of SARS-CoV-2 protein by an antigen test, a suspect test is an antibody test that looks for a response of your immune system to infection with Covid-19, these don’t detect Covid-19 virus directly, uses blood. Diagnostic tests that include current infections are antigen tests and nucleic acid tests. Antibody tests are for past infections.

Test positivity rate

Useful indicator of whether enough testing is happening and how widespread infection might be. However, if mostly symptomatic people are tested (ex: if there are not enough tests or they are expensive)l positivity will be higher than in the general population

Disease burden

Another way of organizing diseases, the overall impact of a health problem on a population, includes financial, social, and health-related costs. DALYs are used to measure this. We can see that disease burdens for high income countries are very different from low-income countries.

DALYs

This value describes a disease. Measure of overall disease burden, expressed as the cumulative number of years lost due to ill-health, disability, or early death. A valid concern is that a lot of information gets reduced to a single number. Does this by adding years of life lost and years lived with disability. This helps governments, global health organizations, and researchers to compare the burden of different diseases across the world and measure both fatal and non-fatal health outcomes. Examples are any diseases like malaria, heart diseases, and more. Another thing is that the burden of a disease can be different for those of all ages, like symptoms can be different for an older person compared to a younger person, seen in Covid

Disease definition

Disease can have a lot of different definitions. The World Health Organization defines disease as the opposite of health, and health = a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. Wikipedia defines disease as a particular abnormal condition that negatively affects the structure or function of all or part of an organism. A disease is often known to be a medical condition that is associated with specific symptoms and signs

Aging

Aging is not classified as a disease and you can’t die of “old age”. Aging can lead to chronic disease that can make you die like Alzheimer’s disease, cardiovascular disease and more. Aging populations lead to increased healthcare costs due to chronic disease management, greater demand for long-term care and support services.

Body mass index

The screening tool used to assess whether a person’s body weight is appropriate for their height, helps estimate if someone is underweight, normal weight, overweight, or obese. Does not measure body fat directly, and may not be accurate for: athletes or muscular individuals, older adults, people from different ethnic groups. BMI is linked to the risk of various diseases if too high or too low, including diabetes, heart diseases, and more. It equals weight divided by height 

Gut microbiome

Helps digest food, can have a big impact if you are overweight or not, also helps regulate the immune system. Strong link between gut microbiome and composition and body weight. A reduced diversity in the microbiome leads to more weight gain

Fecal transplantation

Fecal matter from a healthy donor is transplanted into the gut of a patient, the goal is to restore healthy gut microbiota in individuals with dysbiosis. Gut microbiota affects body weight and metabolism. It is a potential treatment for obesity and not yet real

Etymology

The study of the origins of words

Disease etymology

Early 14th century, from the old French disease discomfort, from des-”without, away” + aise “ease”. Malaria is an example for “bad air”: it was thought that malaria came from breathing in the rotting stench of marshes and swamps

Societal and personal impacts of disease names

They carry power, shape public perception, and can have real-world consequences for individuals, communities, nations, and healthcare systems. Personal impacts: they may shame or label individuals negativity. People may face social rejection, job discrimination, reduced self-esteem, delayed healthcare seeking. An example of this is Hansen's disease is the modern name for leprosy, helping reduce stigma. Can also lead to Blame and xenophobia, can lead to racism, like with the Spanish Flu or China virus. Also economic problems like seen with the Swine flu and people stopped getting pork.

WHO guidelines on naming diseases

Avoiding things like geographic locations, personal names, cultural or ethnic references, animal species. Use things like generic descriptions, severity, affected population, or the pathogen that caused it. It is used to prevent unnecessary negative impacts on trade and travel, tourism and business, groups of people, animals or food products. An example is COVID-19, CO=corona, VI=virus, D=disease, 19=year discovered.

Infection

Invasion by an multiplication of pathogenic microorganisms in a bodily part of tissue. Microorganisms: being small is a prerequisite for infection. Pathogenic: capable of causing disease. Examples include bacteria, fungi, viruses, protists, helminths.

Types and sizes of pathogenic microorganisms

• Viruses: cellular infectious agents composed of genetic material (DNA or RNA) enclosed in a protein coat. Examples: influenza virus, HIV, SARS-CoV-2. Size range: 20 to 300 nanometers, smallest pathogens; require host cells to replicate

• Bacteria: single-celled prokaryotic organisms: have cell walls and sometimes flagella or pili. Example: tuberculosis, staphylococcus aureus. Size range: 0.2 to 10 micrometers in length. 

• Fungi: eukaryotic organisms, can be unicellular or multicellular. Examples: yeast, aspergillus species like molds. 3-10 micrometers have hyphae that are several micrometers wide. 

• Helminths: multicellular parasitic worms; visible to the naked eye in adult form. Examples: foundworms, Size range: from a few millimeters to several meters in length.

local/systemic/focal infections

• Local: infection confined to a small region of the body, ex: boils and impetigo. 

• Systemic: widespread infection in many systems of the body; often travels in the blood or lymph, ex: sepsis and pneumonia

• Focal: infection that serves as a source of pathogens for infections at other sites in the body. Ex: wound infections and tonsillitis

Primary vs secondary infections

• Primary: initial infection within a given patient. Ex: chickenpox and HIV

• Secondary: infections that follow a primary infection, often by opportunistic pathogens, not normally capable of causing disease in a healthy host. Example is the bacterial pneumonia following influenza

acute/chronic/latent infectious disease

• Acute: disease in which symptoms develop rapidly and that runs its course quickly. Example: influenza virus that lasts a few days to 2 weeks

• Chronic: disease with symptoms that develop slowly and last a long time. Examples: a combination of genetic, lifestyle, and metabolic factors. Type of chronic non-infectious disease, it is lifelong.

• Latent: disease that appears a long time after infection. Example: herpes simplex virus type 1 or 2

Opportunistic pathogens

Microorganisms that do not usually cause disease in healthy individuals but can cause infections when a person’s immune system is weakened or when they gain access to normally sterile parts of the body. Often part of the normal microbiota like the gut, skin, and stuff like that. Becomes harmful in immunocompromised hosts like people with HIV. Can also infect after trauma.

(non)communicable and contagious diseases

• Communicable: disease transmitted from one host to another, example: tuberculosis

• Contagious: communicable disease that is easily spread, example: measles

• Noncommunicable: disease arising from outside of hosts or from opportunistic pathogen, example: high blood pressure, legionnaire’s disease

mechanisms of disease transmission

• Direct contact: like hand touching with someone who is infected. Person to person contact. Also droplet spread, short range respiratory droplets from coughing, sneezing or talking seen with Covid-19. 

• Indirect contact: touching a door knob after someone who is infected touches it. Airborne transmission: infectious agents are carried by dust or droplet nuclei suspended in air. Vehicle-borne transmission: spread via contaminated inanimate objects (fomites). Vector-borne transmission: carried by living organisms typically insects like mosquitoes, ticks, or fleas like malaria

• Airborne transmission: droplets remain airborne longer in dry air, respiratory transmission is the dominant mode of transmission for SAR-CoV-2 like sneezing, coughing, spitting, and speaking. Masks reduce airborne transmission, protecting others and self.

• Bodily fluids like blood, vomit, pee, poop, sweat, semen, spit, other fluids 

• Fecal contamination of food/water

Fomites

Inanimate objects or materials can become contaminated with infectious agents and serve as vehicles for indirect transmission of disease to a new host. These objects don’t cause disease themselves but can transfer pathogens when touched or used by a susceptible person. They are part of the vehicle-borne transmission pathway. Pathway: infected person contaminates an object by touching, coughing, sneezing, or bleeding on it, pathogen survives on the surface for a certain period, another person touches the contaminated object and then touches their mouth, nose, eyes, or open wound, allowing the pathogen to enter their body. Example is the Norovirus spreading via contaminated door handles.

Half-life of pathogenic agents

The time it takes for half the amount of a pathogen to decay, degrade, or lose viability in a specific environment. How long a pathogen remains infectious on surfaces, in air, water, or other media, and it directly affects the risk of indirect transmission, especially via fomites, aerosols, or contaminated materials. Factors that affect this include type of surface or material, temperature, humidity, UV light or sunlight exposure.

Surface disinfectants and copper

• Surface disinfectants and copper impact the survival of pathogens on surfaces is key to interrupting indirect transmission, especially fomite transmission. Surface disinfectants are chemical agents used to kill or inactivate pathogens on inanimate surfaces, it reduces the bioburden on surfaces, breaks the transmission chain by removing the pathogens. Example: SARS-CoV-2 can survive on plastic or stainless steel for up to 72 hours. 

• Copper and copper alloys are naturally antimicrobial - they kill or inactivate pathogens on contact. Copper releases ions that disrupt microbial membranes, proteins, and nucleic acids. Pathogens that are inactivated by Copper: MRSA, E. coli, influenza virus, SARS-CoV-2.

Soap and hand sanitizers

• Essential tools in preventing disease transmission via contact, especially through fomites and person-to-person contact. They work by removing or killing pathogens on the hands, which are one of the main vehicles for transferring microbes to the mouth, nose, eyes, or surfaces. Soap contains surfactants that break down the lipid membranes of many viruses and bacteria. Effective against enveloped viruses and bacteria. 

• Hand Sanitizers are alcohol-based containing 60-95% ethanol or isopropanol. It denature proteins and disrupt lipid membranes, inactivating many pathogens. Effective against enveloped viruses = SARS-CoV-2, some bacteria. 

• During the COVID-19 pandemic, alcohol-based hand sanitizers became a frontline defense, especially in settings where you couldn’t wash your hands.

Relative size of virus particles and droplets and aerosols

• Relative size of virus particles, droplets, and aerosols is key to knowing how disease spreads, especially via the airborne and droplet routes. Size affects how far particles travel, how long they stay in the air, and what kind of protection is effective. Virus particles are usually 20-300 nanometers, viruses are not airborne they hitch a ride on droplets or aerosols, too small to see. 

• Respiratory droplets: 5-10 micrometers in diameter, expelled when coughing, sneezing, talking, or breathing. Heavier - usually fall to the ground within 1-2 meters, responsible for droplet transmission. Examples: COVID-19.

• Aerosols = less than 5 micrometers, can include individual virus particles suspended in air or smaller dired-down droplets. Stay suspended in the air for minutes to hours, can travel long distances on air currents, responsible for airborne transmission.

Social distancing and masks as means to reduce airborne and droplet transmission

• Airborne and droplet transmission are key mechanisms through which many infectious diseases spread - especially respiratory illnesses like COVID-19. Social distancing and mask use interrupt the transmission chain by targeting how pathogens travel through the air. 

• Masks work by blocking/filtering droplets and aerosols containing infectious agents, wearers and others too. Cloth masks block droplets but not aerosols. Surgical Mask blocks droplets but partially blocks aerosols. N95 masks block both droplets and aerosols. Masks significantly reduced transmission of COVID

• Social distancing increases physical distance between people reducing the chance of inhaling infectious droplets or aerosols, reduces contact rate. It is effective mainly for bigger droplets, aerosols can float further but distancing still reduces concentration exposure. 

Types and models of action of face masks

• Cloth Masks: low to moderate filtration, it can block droplets but not aerosols because it has a lot of gaps due to the material

• Surgical masks: can block out droplets but not much of aerosols, it was never intended to be used as to fight against COVID

• N95 masks are tight-fitting with high filtration of small particles, it has an electrocharged layer that helps block things out, this is very good in fighting droplets and aerosols.

PPE

Specialized clothing or equipment worn by individuals to protect themselves from exposure to infectious agents, hazardous substances, or contaminated environments. This includes gloves, gowns, face masks, eye protection, and a lot more. During COVID-19 PPE was needed in order to limit the transmission of the disease.

Oral-fecal route of disease transmission

Can be seen as the contamination of food/water, this is when you don’t wash your hands well enough after you use the restroom causing fecal matter to be present in food. Examples of disease that have been seen like this are typhoid fever, polio, and foodborne illnesses.

S-I-R model of disease spread

• Susceptible: not yet infected

• Infected: capable of spreading 

• Recovered: immune; no spreading

• A mathematical model used to describe how infectious diseases spread in a population over time. It predicts how fast an infection spreads, estimates peak infection levels, determines whether an outbreak will grow or fade.

R0 and Rt (the basic and effective reproduction number)

• R0 is the basic reproduction number, if it is less than one then the infection will not spread but if it is more than 1 then epidemic will occur. The larger R0 is the harder it is to stop an epidemic. R0 is the average number of new infections that one infectious person generates, in an entirely susceptible population, during the time that person is infectious. Depends on: duration of infectious period, probability of infecting susceptible individuals during one contact, number of susceptible individuals contacted per unit of time.

• Rt = effective reproductive number, the expected number of new infections in a population where some individuals are no longer susceptible. If Rt>1 the disease is spreading, =1 disease is stable, <1 disease is declining. Reflects the current rate of disease transmission. Indicator used in real time to monitor and respond to outbreaks. 

Ways to estimate R0

• Contact tracing: identify people who have been in close contact with someone who has tested positive for an infectious disease. Notify, test, isolate, or treat those contacts. Interrupt chains of transmission early. 

• Case tracing: identifying people who have tested positive for an infectious disease. Investigating who they may have infected. Sometimes also looking backward to find the source of their infection. Most useful early in an outbreak when most people are still susceptible

Contact tracing

identify people who have been in close contact with someone who has tested positive for an infectious disease. Notify, test, isolate, or treat those contacts. Interrupt chains of transmission early. 

Case reporting

identifying people who have tested positive for an infectious disease. Investigating who they may have infected. Sometimes also looking backward to find the source of their infection. Most useful early in an outbreak when most people are still susceptible

Epidemic

rapid spread of a disease within a specific population, community, or region over a short period of time. It happens when the number of cases of a disease suddenly increases above what is normally expected in that area. Can result from a new infectious agent being introduced like virus or bacteria. A change in the environmental or social factors like poor sanitation or crowded areas. An example of this is Ebola epidemic

The use of simulation models to understand spread of infectious disease

• They are mathematical or computer-based tools used to mimic how infectious diseases spread in a population over time. They allow scientists and public health officials to predict future outbreaks, estimate key variables, test the impact of interventions, and prepare for different scenarios. 

• Examples are compartmental models (divide population into groups like Susceptible, Infected, and Recovered). This can also be seen with COVID-19, agent-based models used by the CDC to predict hospital strain under various reopening scenarios.

Herd immunity and ways to achieve it

• A herd of Recovered individuals protects Susceptible individuals, herd immunity is about breaking the chain of transmission. You achieve it by vaccination or natural infection. Natural infection is when governments let a population with an epidemic go and allow the people who survive the infection to live with the antibodies and the people who die, die. 

• Occurs when enough people in a population are immune to an infectious disease, making it harder for the disease to spread-even to those who are not immune. Disease spreads from infected to susceptible people, when most people are immune, transmission chains break, this protects vulnerable individuals who can't be vaccinated. Vaccination is safe and controlled, avoids the risk of severe illness or death, and can be scaled quickly. Natural infection: gaining immunity after recovering from illness, risky because it can lead to hospitalizations, deaths, and long-term effects, and may overwhelm healthcare systems. Seen with COVID-19 and led to many deaths.

Vaccine hesitancy

• Delay in acceptance or refusal of vaccines despite availability of vaccination services. There are different factors that go with this: confidence(trust in safety and effectiveness), complacency(perception that the disease is low risk or not serious), convenience (access, affordability). 

• It matters because vaccine hesitancy can lead to lower vaccination rates, increasing the risk of outbreaks. It undermines herd immunity, diseases with high R0 values like measles.

Faroe islands measles epidemic of 1781

• Few people here, 1781 measles epidemic, virus self-readicated, at least 500,000 people required to sustain virus, reintroduced in 1846, individuals old enough to have experienced the disease 65 years previously did not get sick, infection offers lifetime protection. 

• Outbreak demonstrated the impact of waning population immunity in an isolated setting. Herd immunity failure after prolonged absence of a pathogen, lifelong immunity from natural infection, concept of disease reintroduction into a fully susceptible population. 

Pathogen attenuation

• Process of weakening a pathogen so that it can no longer cause serious disease but still stimulates an immune response. Attenuated (weakened) pathogens are used to create live attenuated vaccines that: mimic natural infection, cause little or no illness, stimulate strong, long-lasting immunity, and often require fewer doses than inactivated vaccines. 

• Basically, an attenuated pathogen is a less deadly version of the pathogen that is seen in an epidemic and it is used in the vaccination for antibodies.

Endemic disease

Neither humans nor the disease go extinct, maintained without outside input, depends on new birth

Naive newborns

Infants who have not yet been exposed to pathogens and whose immune systems are undeveloped or immature. Immature immune system: at birth, newborns have underdeveloped adaptive immunity, no prior pathogen exposure: no immune memory. Reliant on maternal antibodies. Many vaccines are scheduled in early infancy to begin building the baby’s own immunity.

Childhood diseases

• Measles (high fever, rash, and MMR vaccine), smallpox , mumps (swollen salivary glands, MMR vaccine), diphtheria, whooping cough (Severe coughing, DTap vaccine). Primarily affects infants and young children, often because of their developing immune system and close contact with others. Immunization schedules are designed to protect the most vulnerable. 

Vaccination

Stimulating a person’s immune system to develop protection (immunity) against a specific disease, usually by exposing the body to a safe form of a pathogen or its parts. Vaccines contain antigens, antigens train the immune system to recognize and fight the real pathogen in the future, and make memory cells. Prevents disease in individuals, protects communities through herd immunity, eliminates or eradicate disease, and reduces disease severity.

Zoonotic diseases

• Transmitted from animals to humans, these diseases can be caused by viruses, bacteria, parasites, or fungi

• Transmission can happen through direct contact, animal bites, contaminated food/water, or insect vectors, like ticks or mosquitoes. Examples are Ebola, SARS-CoV-2. Many pandemics have animal origins, diseases pose a global health, food safety, and economic threat, especially where human-wildlife interaction increases.

Bushmeat and wet markets

• Bushmeat is seen in African places where they go to hunt in the jungle and get this meat but it is they get more susceptible to Ebola virus due to this meat but they can’t stop eating it because bushmeat is their primary protein source, it is cheaper that other sources or protein, they have a cultural significance. 

• Wet market is a marketplace that sells fresh meat, seafood, produce, and other perishable goods. In certain conditions - especially the sale and slaughter of live animals in crowded, unsanitary environments, can increase the risk of zoonotic disease transmission. With multiple species there is a risk for a virus spillover. As well as cross-contamination. This can be seen with the Wuhan market with COVID

Bats as natural reservoirs of viruses

• Natural reservoirs some of which have led to disease outbreaks in animals, this can be seen with Ebola SARS-Cov-1 and 2, MERS. They pass disease through indirect contact, intermediate hosts (pass from bats to another animal to humans)

• Their unique biology allows them to carry and spread viruses without becoming ill. Human behavior increases risk of spillover

Spillover zoonoses

Infectious diseases that are transmitted from animals to humans, typically when a pathogen spills over from a non-human animal reservoir to a human host. Often originate in wildlife reservoirs like bats or primates. Human behaviors are major spillover drivers. Some spillovers remain isolated, others like COVID cause global pandemics. The Ebola virus is believed to be spilled over from bats to humans via contact with infected wildlife or bushmeat.

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

Wuhan market had live animal and seafood markets, there were no bats sold at the market but the conditions led to diseases. The cluster of earliest COVID-19 cases center around the Huanan market in Wuhan. Cluster of SARS-CoV-2 positive environmental samples, spatially associated with vendors selling live mammals. Two distinct SARS-CoV-2 lineages, suggesting two cros-species separate transmission events into humans, one of these lineages became the COVID-19 pandemic.

Lab leak theories

There is lab next to the Wuhan market and they were conducting research on SARS-like bat coronaviruses since 2005, there is a theory that it is their accidental or intentional for the release of SARS-CoV

Vector-borne diseases

Illness caused by a pathogen (virus, bacteria, or parasite) that is transmitted to humans through the bite or contact typically of a blood-feeding arthropod like mosquitoes, ticks, or fleas. A vector is a living organism that can transmit infectious pathogens between humans or from animals to humans. This includes malaria and lyme disease.

Plasmodium life cycle

Mosquitoes ingest the parasite by feeding on blood from an infected human carrier. Paramistes reproduce sexually in the midgut of the mosquito and migrate to the salivary glands. Parasite is transmitted when an infected mosquito takes a blood meal. Within 30 minutes parasites reach and infect liver cells, and for 5-16 days multiply inside (no symptoms). Parasites re-enter the blood stream, infect red blood cells and multiply. Infected blood cells burst, releasing new parasites, which infect more blood cells. Some develop gametocytes. Periodicity of cycles corresponds with typical chill/fever symptoms and the Plasmodium species.

Vector control

Strategies, methods or interventions used to reduce or eliminate the populations of disease-transmitting organisms, like mosquitoes, in order to prevent the spread of vector-borne disease. For malaria there are a lot of different vector controls, like draining swamps where there are mosquitoes breeding grounds. Also releasing fish like western mosquitofish that eats the mosquitoes. Also Paris Green which is an insecticide and is very toxic, and kerosene oil which is used on top of swamps in order to stop the larva stage. DDT is also used for adult mosquitoes. Another vector control is releasing genetically modified mosquitoes, a controversial issue because people don’t want to be test subjects and you don’t know what would happen if it fails. Male mosquitoes engineered with gene drive technology produce significantly more males than females. This was seen in Florida where people didn’t want to be test subjects.

DDT

This is very effective at killing mosquitoes but it has a lot of side effects like affecting wildlife, causing cancer, and endocrine disruptors. Banned in the US 1972. Also affecting bald eagles. It is still being used in some regions where malaria is endemic, applied to interior walls of houses.

Indoor residual spraying

When DDT is used to spray on interior walls of houses. Proven, effective to reduce diseases like malaria by killing mosquitoes that rest indoors after feeding, most effective in areas where mosquitoes bite at night and rest indoors. This is seen in South Africa. It is a controversial idea because it helps with malaria but it has a lot of side effects. The World Health Organization is having a total phase-out of DDT in the works.

Bed netting

Netting or window screens to exclude mosquitoes, most feeding happens during the night. Bed nets responsible for 68% of 663 million prevented cases of malaria in Africa between 2000 and 2015, compared to 10% by insecticides.

Anti-malarial drugs

• Designed to prevent or cure malaria

• Quinine comes from the bark of the cinchona tree and then becomes an ingredient in the gin and tonic, it is the tonic.

• Chloroquine - synthetic derivative of quinine

• Hydroxychloroquine - hydroxy group reduces side effects

• The problem is that Plasmodium has become resistance to this drugs

• Artemisinin is effective against all forms of multi-drug resistant P. falciparum, mode of action known. Can be produced through synthetic biology (bionengineered yeast cells). Chinese researchers started looking for an anti-malarial drug because there were casualties among their soldiers due to malaria.

Drug-resistant Plasmodium

Plasmodium parasites that survive anti-malarial drugs. Makes treatment harder, risks resurgence of malaria. Artemisinin resistance in Southeast Asia. P. falciparum in Cambodia resistant to ACTs. Combination therapies, monitoring, new drug development.

Malaria vaccine

• RTS, S/AS01 (mosquirix). To be used for the prevention of P. falciparum malaria in children living in regions with moderate to high transmission as defined by WHO. Partial protection (only 30-40%). The vaccine is designed to prevent the parasite from infecting the liver. Based on recombinant sporozoite protein of Plasmodium falciparum.

• Four-dose regimen, is that practical?

• $5 per dose, $325 million per year, who is paying?

• Neglect of existing malaria control measures

• Safety concern (side effects)

• No informed consent in one of the pilot trails (colonial science)

Covid-19

Etiology: caused by SARS-CoV-2, a novel coronavirus. Symptoms: fever, cough, fatigue, anosmia, shortness of breath, etc. Diagnosis: RT-PCR is gold standard, antigen tests also used. Treatment: antiviral, steroids, oxygen, supportive care. Prevention: vaccination, masking, distancing, ventilation. Impact: massive global health, social, and economic consequences.

Breaking tulips

a striking color pattern - streaks or flames of contrasting color on the petals. Plant virus in the genus Potyvirus in the family potyviridae, interferes with anthocyanin pigment in petals. Transmitted by aphids, spread through infected bulbs or mechanical means. Means a virus that causes a breaking pattern in the coloration of tulip flowers, started in the Netherlands in the 16th and 17th centuries. There is no cure so to prevent it, identify and destroy infected tulips to prevent spread, use virus free bulbs, and have aphid control (Vector management). This can lead to an economic loss since it was very valuable at the time and since virus free tulips became rare, the prices soared. Had cultural and financial consequences in Dutch society

Thrombophilia

Caused by inherited genetic mutations or acquired conditions that increase the risk of abnormal blood clot formation. It means the tendency or affinity for clotting. This is seen in Factor V Leiden mutation that was discovered in 1994. Signs and symptoms: swelling and pain in a limb, chest pain, shortness of breath. Treatment focuses on preventing and managing blood clots. Prevention = reducing the risk of clot formation, like lifestyle modifications, medicine, avoiding risk factors. Can lead to lifestyle limitations

The Dutch Elm disease

First described by a Dutch plant pathologist in the 1920s, it is a disease in the American elm tree, a fungal infection that killed millions of elm trees across Europe and North America, transformed urban and rural landscapes and forced new approaches in disease management. Caused by infection with a fungus called Ophiostoma ulmi. The vector is the elm bark beetle, Found in the Netherlands. Prevention is control of elm bark beetles, sanitation, and proper tree care. Personal impacts, the loss of trees in your home, societal impacts = loss of elm populations reducing biodiversity, economic impacts.

Pott’s disease

• Caused by Mycobacterium tuberculosis infection of the spine. Named after Percivall Pott, an English surgeon who first described the spinal tuberculosis condition in the 18th century. It is not contagious. Disseminate from a primary infection site through the bloodstream or lymphatic system to the vertebrae. Symptoms and Signs = chronic back pain, localized tenderness, muscle spasms, weakness in limbs, loss of sensation. Treatment = antibiotics, immobilization, or surgical intervention. Preventing it is not getting tuberculosis

Cystic fibrosis

One of the most common life-shortening inherited diseases in the US, mutation in the CFTR gene (cystic fibrosis transmembrane conductance regulator), overproduction of mucus clogs airways, makes it hard to breathe. Chronic infection with slime-producing bacterium Pseudomonas aeruginosa. Discovered in 1989, it is not contagious, higher in people with European ancestry. Affected lungs, pancreas, digestive system, respiratory system. You can newborn screening and genetic testing to find out if you have it. There is no cure. But airway clearance techniques can help. No way to prevent it. Personal impacts = reducing life expectancy, impacts on education, many burdens like emotional and financial. Societal: high health care costs, research investment

Berberi

Etiology = caused by deficiency of vitamin B1 in diet. Beriberi comes from the word Sinhalese language for “I cannot, I cannot”. Origins = polished (white) rice lacks the vitamin and a lot of people ate it causing them to get sick. It is not contagious but because of diets. The rice bran contains a substance that counter-acts the toxic effect. The Anti beriberi factor is thiamin (aka vitamin B1). Symptoms include fatigue, confusion, memory problems, and pain. Diagnosis: clinical signs and symptoms, blood test showing vitamin levels. Treatment = getting more of the vitamin. Prevention: having a balanced diet. Personal impacts = severe neurological damage, heart failure, or death. Societal impacts: caused a widespread illness and death in populations who were dependent on polished rice. Led to advances in nutrition science and public health policies. This is an environmental disease, not enough of a good thing

Goiter

Etiology is the enlargement of the thyroid gland which is caused by iodine deficiency, autoimmune disease, tumors, or hormonal imbalances. Etymology, guttur in latin means throat, describes the noticeable swelling in the neck due to thyroid enlargement. This was seen in the ancient times where iodine in the soil and food was lacking, during early Chinese and Greek times. It is not contagious, happens in regions with low iodine levels. Still common in places where iodized salt isn’t used, like Africa. Symptoms and Signs = swelling of the neck, tight feeling of the throat, coughing hoarseness, can be seen with hyperthyroid symptoms, it is non-toxic. Diagnosis can be because of an examination, also blood tests. Treatment: better iodine intake, through iodized salt. This disease can affect cognitive and development delays

Scurvy

Deficiency of vitamin C which is essential for collagen synthesis, wound healing, iron absorption, and immune function. Leads to connective tissues weaken. Also known as vitamin C deficiency. Origins = linked to sailors during long sea voyages in the 15th-18th centuries, helped when people started to bring citrus fruits to prevent scurvy. Needed fresh produce. Happens when people don't have a lot of vitamin C. Symptoms and Signs = swollen bleeding gums, pain, swelling, weakness, fatigue, anemia, internal bleeding, and death. Treatment = vitamin C supplementation. Prevention = regular intake of vitamin C through diet through citrus fruits, berries, and veggies too.

Autism

Neural development disorder impaired social interaction repetitive behavior. Causes include genetic factors, neurobiological factors, environmental factors. Recognized as a distinct condition in the 1940s by Leo Kanner. It is neurological and developmental. There is no cure, but therapy can help it. Can affect learning, communication, independence, and relationships. This leads to an increased need for specialized educational and health services as well as economic costs. Can cause stigma

Drapetomanoa

Etiology a false mental illness proposed in 1851 by American physician Samuel A. Cartwright, who claimed it caused enslaved Africans to flee captivity. Condition to negroes being treated as equals or with too much freedom - a completely unfounded and racist belief. There is no scientific or medical basis for it, the desire to escape slavery is a natural response to oppression not a disease. Drapetomania is the madness of running away. Coined by Samuel A. Cartwright in the American South in 1851. Medicine to justify slavery. Spread ideology in the pre-Civil War US. Cartwright even suggested that the condition could be prevented by beating slaves or treating them a certain way. Symptoms and Signs: irrational desire to escape servitude, normal human resistance to slavery.

Obesity

Excess adipose tissue, this can be measured by hydrostatic weighing, skinfold thickness, and BMI. Obesity is considered a chronic imbalance between calories consumed and calories expended. This is highly prevalent worldwide, common in high income countries where people can eat a lot. Symptoms and signs are excess body fat and there are physical limitations, this is a risk factor for things like type 2 diabetes, high blood pressure, high cholesterol, and more. You can diagnose this for BMI. This disease can be prevented by factors like diet, changes in the way you eat, lifestyle changes (exercising more but its not always a matter of choice either). Genetics can also have a factor in this (a common variant in the FTO gene is associated with body mass index and predisposes to childhood and adult obesity. There is also an obesity-associated gut microbiome, it has been shown that some people have a gut microbiome which increases their weight. There is also a study where fecal transplants can help with obesity. Reducing the prevalence of obesity = drugs (suppress appetite, slow gastric emptying, concerns of side effects), surgery, taxing sugar.