4.1:COMMUNICABLE DISEASES, DISEASE PREVENTION IMMUNE SYSTEM

• diseases are caused by pathogens
• types of pathogens

  bacteria

  virus

  Protoctist

  fungus
• viruses are non living and acellular and they are smaller than bacteria
• viruses consists of only genetic material and can only replicate when inside the host cells
• viruses involve injecting their nucleic acid into the host cells
• protoctist are eukaryotes that exist as single celled organisms
• very few protoctist are pathogens but the ones that are pathogens are extremely dangerous
• pathogenic protoctist are parasites usually transmitted through a vector eg malaria
• fungi are eukaryotes
• fungi mostly affects plants
• fungi can be single or multi cellular
• pathogenic fungi are parasitic that are able to release enzymes that digest host tissues and feed off them