Infection

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Ways Infectious Diseases Spread

• Infectious disease can spread by
  • Direct or close contact 
    • Transmission within 1-2 meters
  • Indirect contact
    • Transmission outside of 1-2 meters 
    • Can be on surfaces
• Vectors (organisms that transmit pathogens from an infected host to a susceptible host)

Direct Contact

• Person to person transmission (within 1-2 meters)
• Direct physical contact through kissing, touching, sexual intercourse, etc
• Droplet sprays
• Examples:
  • COVID-19, droplets and direct physical contact
  • EBOLA, direct contact with bodily fluids, semen
  • Note that both COVID-19 and EBOLA can be spread by both direct and indirect contact

Indirect Contact

• Outside 1-2m

• Involves: 

  • Fomites (inanimate objects) become contaminated by pathogens from an infected individual. Transmission to new host via touch and entry into a susceptible portal (e.g. COVID-19)
  • Or spreading as aerosols (smaller particles that can travel further), e.g. COVID-19

• Some pathogens, e.g. measles virus, remain viable in the air for large amounts of time

Vectors

• Diseases can also be transmitted by a vector
• Mechanical vectors
  • An animal (typically an arthropod) that carries the pathogen from one host to another without being infected itself, e.g., a bat
• Biological vector
  • The pathogen reproduces within a biological vector that transmits the pathogen from one host to another, e.g., mosquito (technically the malaria pathogen)

Controlling Infectious Diseases

• Control of infectious diseases refers to the actions and programs aimed at:
  • Reducing the number of new infections
  • Reducing disease prevalence
  • Completely eradicating the disease
• This can be achieved by:
  • Physical precaution measures
  • Medication
  • Vaccines

Physical Precaution Measures

Washing hands

• Hand washing with soap removes pathogens from hands
• This helps prevent infections because
  • People frequently touch their eyes, nose and mouth without even realising it
  • Pathogens can be transferred to food and drinks where they can potentially multiply and be ingested
  • Preventing spread by indirect contact where pathogens can be transferred to fomites, then to another person’s hands

Wearing Gloves

• Prevent contamination
• ONLY WORK WHEN USED CORRECTLY IN APPROPRIATE CIRCUMSTANCES
  • When cleaning and disinfecting the area around the person who is sick or other surfaces that may be frequently touched in the home
  • When touching or having contact with blood, stool, or bodily fluids, e.g. saliva, vomit, mucus, urine
• After using disposable gloves, dispose of them
• Wash hands after removing gloves

Wearing Masks

• Masks act as a simple barrier to help prevent respiratory droplets from travelling into the air and onto other people when the person wearing the masks sneezes, coughs, talks, or raises their voice
• Wash hands after handling a used mask