Topic 5 – Health, Disease and the Development of Medicines- Causes of Disease Flashcards
define health
A state 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?
disease that cannot be transmitted between individuals
generally long lasting with slow onset
caused by lifestyle, environmental and genetic mutations
what is a symptom?
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 chlorea
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? (biology only)
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 DNA into 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
Use of condoms and protected sex
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
