infectious disease

What are infectious disease?

A disease is a condition that causes the body to function less effectively. It also produces specific signs and symptoms.

Signs

  • Signs of a disease can be observed or measured

E.g. Rashes, fever, coughing, vomiting

symptoms

  • Symptoms of a disease can be described or felt by the patient

E.g. Headaches, fatigue, nausea

Infectious diseases

  • Can be spread from one person to another

  • Caused by disease causing organisms called pathogens (e.g. viruses and bacteria)

E.g. Influenza, pneumococcal disease, HIV

Non-infectious disease

  • Cannot be spread from one person to another

  • Usually inherited or caused by factors such as malnutrition, environmental factors or lifestyle choices

  • Not caused by pathogens

E.g. Coronary heart disease, Type 2 diabetes

How are infectious diseases spread?

  • Droplets in the air

    • Respiratory droplets may contain pathogens. Anyone within close range may breathe in these droplets

  • Direct contact

    • Infected person may infect another person through exchange of body fluids during sexual intercourse; mucous membrane or an uninflected person; bloodstream

  • Contaminated food and water

    • May contain pathogens when food and water are not properly stored of handled

Influenza

Causes: influenza virus

How is it transmitted: by droplets in the air, when a person touches an object or surface contaminated with the virus and then touches his/her own mouth/nose/eyes

Signs and symptoms: high fever, headaches, stuffy nose, cough, sore throat and muscle aches

Methods to reduce transmission: get influenza vaccination, take antiviral drugs as prescribed by doctor to treat the illness

Pneumococcal disease

Causes: pneumococcal bacteria

How it is transmitted: mainly by respiratory droplets

Signs and symptoms: fever, headache, vomitting, cough, chest pain and rapid breathing

Methods to reduce transmission: get pneumococcal vaccination, take antibiotics as prescribed by doctor to treat the disease

Methods to reduce transmission for both influenza and pneumococcal disease.

  • Avoid coming into close contact with people who have the virus

  • If you are sick, cover mouth and nose when you cough or sneeze and dispose of used tissue properly. Wear a mask if unwell.

  • Wash hands with soap and water if you think you have touched contaminated objects

Definition: A vaccine contains an agent that resembles a pathogens and prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when the pathogen invades.

How do vaccines work?

  • Substances that trigger the production of antibodies are called antigens. E.g. the proteins on the surface of pathogens.

  • When a vaccine, which contains an agent resembling the pathogen enters the bloodstream, it stimulates white blood cells (lymphocytes) to produce antibodies.

  • Antibodies are specific in action in destroying one type of pathogen. It can also tag pathogens for destruction by other white blood cells (phagocytes).

  • Some white blood cells remain in bloodstream. If a live pathogen enters the bloodstream, the white blood cells will recognise them and more quickly produce the antibodies needed to destroy the pathogens before they can infect cells.