Communicable (Infectious) Diseases (AQA GCSE Biology: Combined Science)

What is a communicable disease?

• A disease is an illness or disorder of the body or mind that leads to poor health
• Communicable/infectious diseases are caused by pathogens and are transmissible (can be spread between individuals within a population)
  • Both plants and animals can be affected by pathogens

Infectious & non-infectious diseases table

	Definition	Examples
Infectious disease	Disease caused by a pathogen that passes from infected individuals to uninfected individuals Also known as communicable disease	Cholera, HIV/AIDS, malaria, tuberculosis
Non-infectious disease	Long-term diseases that are not caused by pathogens	Lung cancer, cardiovascular disease, depression, cystic fibrosis, vitamin deficiencies

• Many microorganisms are pathogens including:
  • Bacteria: reproduce rapidly and can produce toxins which damage tissues of the body
  • Viruses: reproduce rapidly within host cells causing cell damage
  • Fungi
  • Protoctists
• To control disease, it is very important to know what pathogen is causing it

Controlling the spread of disease

• Transmission occurs either through direct contact, contaminated water or in droplets carried in the air
• The simplest way to prevent disease is to stop pathogens from spreading
• Controlling the spread of disease can be done through
  • good hygiene
  • effective sanitation 
  • waste disposal

Methods to prevent spread of pathogens

Measure to prevent spread	Explanation
Hygienic food preparation	To prevent direct contact transmission keep food cold to slow bacteria and fungi reproduction wash hands and clean surfaces to avoid contamination cook food thoroughly to kill pathogens use separate utensils for uncooked meat and cover food to prevent contamination
Personal hygiene	To prevent direct contact transmission washing with soap, especially after using the bathroom, to remove pathogens To prevent airborne transmission use tissues to catch sneezes and coughs and dispose of used tissues
Waste disposal	To prevent direct transmission: dispose of waste food to prevent prevalence of flies which act as a vector cover rubbish bins and remove to the landfill for disposal or burning regularly
Sanitation	To prevent waterborne transmission: homes and public places should have plumbing and drains to remove faeces and waste safely; these drains can carry pathogens raw sewage should be treated to remove solid waste and kill pathogens before being released into the environment

Other methods to reduce transmission in the population

• Vaccinations which reduce the likelihood of transmission
  • This is covered in more detail here
• Destroying vectors that carry the disease
  • This is covered in more detail here