Diseases and Pathogens
Concept: Meaning of Diseases and Pathogens
What is a disease?
- Any disorder or malfunctioning of the body or mind that leads to impaired mental and physical health is considered a disease.
- Every disease has a particular set of characteristic symptoms to identify the type of disease.
Classification of Diseases:
- Based on origin/onset:
- Inherited diseases: The diseases which are passed from parents to their offspring.
- Acquired diseases: The diseases which develop after birth due to different environmental factors.
Examples : Haemophilia, sickle-cell anaemia.
Examples : Influenza, malaria.
- Based on transmission:
- Communicable diseases: Such diseases spread from infected persons to healthy persons. They are also called infectious diseases.
Examples : Measles, chicken pox.
- Non-communicable diseases: Such diseases do not spread from the infected person to a healthy
person. They are also called non-infectious diseases.
Examples : Diabetes, cancer.
- Based on duration:
- Chronic diseases: The diseases that continue for a long time and may worsen over time. Such diseases cannot be cured but can be controlled.
- Acute diseases: An acute disease appears suddenly and lasts for a short time. This is different from chronic diseases that develop gradually and last for months.
Examples : Arthritis, heart diseases.
Examples : Pneumonia, appendicitis.
- Based on causal organism:
- Viral diseases: Diseases that are caused by viruses.
- Bacterial diseases: Diseases that are caused by bacteria.
- Fungal diseases: Diseases that are caused by fungus.
Examples : Flu, herpes.
Examples : Cholera, tuberculosis.
Examples : Athlete’s foot, ringworm.
What are pathogens?
Classification of microbes:
- Bacteria (singular: bacterium) are single-celled organisms that are found in the natural environment.
- They reproduce very quickly.
- Bacteria are found on decaying things, inside human body and in air, water and soil.
Examples : Escherichia coli, Streptococcus pyrogenes.
- The size of a virus is smaller than a bacterium.
- They are an intermediate between living and non-living organisms.
- They need a host body to multiply. Without a host, they act as non-living organisms.
- They cause diseases, such as chickenpox and rubella, and many of these diseases spread from infected persons to healthy people.
Examples : Influenza virus, Herpes virus.
- Fungi have some plant-like features like the presence of small roots called rhizoids, but they do not perform photosynthesis due to the absence of chlorophyll.
- All fungi are not microscopic, and some are visible through naked eyes (macroscopic).
- Fungi act on dead things leading to their decay.
- The presence of bacteria and fungi in food can cause food poisoning.
Examples : Mushrooms, yeasts, moulds.
- This group includes microscopic animal-like organisms.
- They depend on other organisms for food.
- They are generally single-celled.
Examples : Amoeba, Paramecium.
- All microorganisms are harmful.
- Salt, sugar, vinegar, and castor oil are natural preservatives used to preserve food for long durations.
- Escherichia coli, a bacterium found in our intestines, helps in digestion.
- Lactobacillus helps in turning milk into curd.
- Yeast is used for making bread.
- Penicillium notatum is a fungus from which an antibiotic was derived for the first time.
- Acetobacter aceti, a fungus that is used for making acetic acid.
- Fungi help in fermentation, a process that converts sugar into alcohol.
Symptoms: The physical or mental problems that a person experiences that indicate the presence of a disease.
Food poisoning: A diseases caused by bacteria or fungi and is accompanied with vomiting and diarrhoea.
Not all microorganisms are harmful. Some of them play a vital role in our lives. Some examples of useful microbes are as follows—