Viruses topic 2

what is herd immunity

a large part of a population becomes immune, making it hard for the pathogen to spread

what is infectious disease

Any disease caused by another organism or organic agent that can be passed from one individual to another (indirectly/directly)

what is a non-infectious disease

non-infectious diseases are those that cannot be transferred from one organism to another

what is a parasite

are smaller than host and may indirectly harm the host by spreading pathogens

what is a protist

single-celled eukaryotic organisms that have their own kingdom, transmitted through many ways such as contamination, contact, etc.

what is a fungal disease

causing by certain fungi and transmitted usually through contact/inhalation

what is a bacterial disease

cause disease by multiplying in the body, releasing toxins that damage cells, causing immune system reaction

what is a virus

non-living, require a host to replicate, and invade host and hijack cells, making it difficult to eradicate without killing host cells. Can be transmitted in many ways such as blood, air, contamination, etc.

what is a prion

a mutated protein, that don’t trigger an immune response, making hard to detect, and can be transmitted via genetics or contamination

what is a pathogen

a biological agent that causes disease or illness to its host

what is a vector

any agent that carries and transmits an infectious pathogen into another living organism

what is an endemic

a disease that is constantly present in organisms of a certain group or living in a particular location

what is an epidemic

the occurrence of more cases of a disease than would be expected in a community or region

what is a pandemic

an epidemic of infectious disease that has spread across a large region

what is a contagious disease

spread from one person to another, typically by direct contact, but not always.

what is a non-contagious disease

a disease which is not easily transmitted from person to person. It may require the aid of a vector (e.g. a mosquito), or it may result from a shared environmental issue like food poisoning.

what is disease transmission in terms of direct body contact

when an infectious person touches another person.

what is disease transmission in terms of contact with body fluids

when an infectious person exchanges fluids with another person

what is disease transmission in terms of contaminated food

foods that can transmit diseases if not properly handled or cooked

what is disease transmission in terms of contaminated water

transmitted usually by the presence of pathogens or chemicals

what is disease transmission in terms of disease-specific vectors

a living organism that transmits a particular infectious pathogen from one individual to another

what is virulence in terms of a disease

virulence of a pathogen refers to its ability to cause disease which can be measured by how many individuals it affects, how quickly it spreads through the body, and how many hosts die due to its infection

pathogenesis

pathogenesis is the chain of events leading up to that disease due to a series of changes in the structure or function of a cell/tissue/organ.

name the four virulence factors and describe them

adhesions factors: ability of a pathogen to adhere (stick) to a molecule membrane on the host cell
invasion factors: proteins that allow pathogens to enter host cells
capsules: an outer layer that covers the cells of many bacterial species
toxins: proteins that poison host cells and cause tissue damage

superbugs

strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics commonly used to treat the infections they cause

where are antibiotics from

antibiotics are produced naturally by bacteria and fungi to kill or inhibit competitors or pathogens

antibiotics vs viruses explain why antibiotics aren’t effective

antibiotics ineffective because viruses lack the structure and metabolic machinery that antibiotics target

antibiotics

antimicrobial chemicals that kill bacteria (bactericidal) or inhibit their growth (bacteriostatic)

immune system (background info)

the body’s three lines of defense against disease-causing organisms, malfunctioning cells, and foreign particles

antigens and why they trigger an immune response

proteins on the surface of invading cells. Antigens are recognised by the immune system as “non-self” and an immune response is initiated

innate vs adaptive immune-response

innate immune-response has the first and second lines of defence, and the adaptive immune-response has the third line of defence
innate is non-specific, adapative is specific to identified pathogens and is only present in vertebrates

first line of defence + example

The first line of defence are the physical and chemical barriers that prevent the entry of the pathogen into the body including skin

second line of defence and what’s in it (2)

A range of defence mechanisms operate inside the body to inhibit or destroy pathogens, including the inflammatory response, and complement system

complement system

they circulate in the blood stream until activated, their main roles include activation of inflammation

Third line of defence

complex steps and different responses including; humoral response (B lymphocytes, antibodies), cell-mediated response (T lymphocytes), and role of memory cells

when does the inflammatory response occur

when tissues are damaged by bacteria, trauma, toxins, heat or any other cause

in the inflammatory response, what are natural killer cells

a type of white blood cell that destroy infected cells and cancer cells in the body

macrophages role in the inflammatory response

ingest and destroy pathogens by phagocytosis

neutrophils in the inflammatory response

first to arrive at the infection site, ingest and destroy pathogens by phagocytosis, and release enzymes that kill pathogens

vasodilation in the inflammatory response

increases blood flow to the area and allows immune response chemicals and immune cells to leak into tissue spaces

prostaglandins in the inflammatory response

control by attracting more and more macrophages to the affected area

what are the measures to control spread of disease

quarantine, hygiene measures, and contact tracing

contact tracing

identifying people who have been in contact with an infected person and asking these people to quarantine

quarantine and how it prevents disease spread

A strict isolation imposed to prevent the spread of disease. It prevents disease spread because humans are isolated and don’t contact with other people so disease can’t spread

what is Ro value

number of people who become infected by a single person with the disease

VT formula

VT= 1 - (1/Ro)

controlling spread of disease via mobility

limit movement of people to minimise disease spread.

controlling spread of disease via immune population

higher the proportion of the population that is immune or have been immunised the less chance there is of a disease spreading

controlling spread of disease via transmission mechanism

refers to how the disease spreads

controlling spread of disease via persistence of pathogens in host

refers to the ability of the pathogen to avoid the human immune system

describe the two pathways of the adaptive immune system

humoral response: b lymphocytes (plasma and memory)
cell-mediated response: t lymphocytes, helper, regulator, memory, killer

describe b lymphocytes and what they do

mature in the bone barrow and move to the lymph glands, defend against antigens outside the cell

describe t lymphocytes and what they do

produced in the bone marrow but move to the thymus gland, respond to antigen fragments that have been processed and presented

what do plasma b cells and memory b cells do

plasma b cells produce antibodies while memory b cells retain a memory of the invader

name and describe the types of t cells

helper: recognise antigens and stimulate b cell division
killer: seek and destroy target cells or antigens
memory: retain a memory of the invader
regulator: control the immune response by shutting it down when antigens are gone

explain how plants defend against diseases

chemical: plant defensins: proteins that inhibit the development of fungi, bacteria and viruses, and plant toxins: deter herbivores
physical: thorns, spikes, bark, leaf hairs

vaccine

are biological preparations that induce immunity to a particular infection

immunity

the body's ability to defend itself against disease-causing agents

naturally acquired passive immunity vs naturally acquired active

passive: antibodies pass from the mother to the fetus via the placenta during pregnancy, whereas, active immunity is when the body produces antibodies and specialised lymphocytes (third line of defence)

artificially acquired immunity passive vs active

passive: preformed antibodies in an immune serum introduced to the body by injection, whereas, active immunity is when antigens are introduced in vaccines, and the body responds to the vaccine through the third line of defence