Causes of disease Flashcards
Define health
Astate of complete physical, mental and
social well-being (as defined by the
World Health Organization, WHO)
Define disease
A disorder of the body or mind that
negatively affects an individual’s health
What are the two types of disease?
● Communicable
● Non-communicable
What is a communicable disease?
● A disease that is passed directly
between individuals
● Caused by a pathogen
Define pathogen
A disease-causing organism e.g. virus,
fungi, bacteria, protists
What is a non-communicable disease?
● A disease that cannot be transmitted between
individuals
● Generally long lasting with a slow-onset
● Caused by lifestyle, environmental conditions, genetic
mutations etc.
What is a symptom?
A change experienced by an organism
that indicates disease
Why does having an illness make an individual more
likely to contract another disease?
A disease may weaken an individual’s
immune system making them increasingly
susceptible to other infections.
Describe cholera
● Caused by Vibrio cholerae bacterium
● Spread by drinking water or washing in water that has
been contaminated with infectious faeces
● Symptoms: diarrhoea, vomiting
How can the incidence of cholera be reduced?
● Access to clean water
● Improved sanitation (sewage disposal etc.)
Describe tuberculosis (TB)
● Caused by Mycobacterium tuberculosis bacterium
● It is an airborne bacteria spread by droplet infection
● Symptoms: lung damage, chesty cough, wheezing
How can the transmission of TB be
reduced?
● Improved hygiene (washing hands, sneezing into
tissues etc.)
● Infected individuals should avoid crowded areas
● Increased ventilation in the individual’s home
Describe Chalara ash dieback
● Caused by a fungus that infects ash trees
● Spread via airborne spores which are carried by the wind
● Causes dark lesions on bark and blackened leaves which
wilt and eventually die
How can the transmission of Chalara ash
dieback disease be reduced?
● Control the movement of ash trees
● Kill infected plants
● Replant with a different species
Describe malaria
● Caused by plasmodium protist
● Spread by mosquito vectors which pick up the plasmodium
protist when feeding on the blood of an infected organism and
transmit malaria to other organisms during feeding
● Flu-like symptoms, damage to red blood cells, liver damage
How can the incidence of malaria be
reduced?
● Mosquito nets
● Insect repellant
● Cover arms and legs
Describe stomach ulcers
● Caused by Helicobacter pylori bacterium
● Transmitted orally by eating infected foods or drinking
infected water
● Symptoms: stomach pain, vomiting, nausea
How can the transmission of Helicobacter pylori be
reduced?
● Access to clean water
● Improved hygiene
● Improved sanitation (sewage disposal etc.)
Describe Ebola
● Caused by Ebola virus
● Spread by direct contact with infected body fluids e.g.
blood, semen, saliva, mucus, vomit
● Symptoms: fever, diarrhoea, vomiting, internal bleeding
How can the transmission of Ebola be reduced?
● Improved hygiene
● Isolating infected individuals
● Sterilisation of outbreak areas
Describe simply how viruses cause disease
They enter host cells and replicate inside
of them. The host cells rupture, releasing
new viruses.
How do viruses differ from other microorganisms e.g.
bacteria, fungi?
Viruses are not living organisms. They
do not reproduce and can only replicate
inside a host cell.
By what two pathways do viruses replicate inside
living cells?
● Lytic pathway
● Lysogenic pathway
Describe the lytic pathway
- Virus binds to specific receptors on host cell
- Virus injects its DNAinto host cell and replicates its DNA
using host cell machinery - New viral structures are produced and assembled
- Host cell ruptures, releasing new viruses
Describe the lysogenic pathway
- Virus binds to specific receptors on host cell
- Viral DNA injected into host cell and becomes integrated into host cell
genome - Viral DNA replicates each time the host cell divides. However, the cell
remains normal. - Trigger causes the activation of viral DNA. It enters lytic pathway
Describe HIV
● Caused by human immunodeficiency virus
● Spread by direct contact with infected body fluids e.g. blood,
semen, breast milk.
● Destroys white blood cells making the individual
immunodeficient and increasingly susceptible to other diseases.
Leads to AIDS.
How can the spread of HIV be reduced?
● Use of condoms and protected sex
● No needle exchange
● Screening blood for HIV
● Deterring infected mothers from breastfeeding
Describe Chlamydia
● Caused by Chlamydia bacterium
● Spread through sexual contact or direct contact with
infected genital fluids
● Can result in infertility
How can the transmission of Chlamydia
be reduced?
● Use of condoms and protected sex
● Screening
