Common Infectious Agents: Bacteria & Viruses - Causes & Examples

Bacteria

Single-celled organisms causing pneumonia, tuberculosis, food poisoning. Example: Streptococcus pneumoniae (pneumonia).

Viruses

Smaller than bacteria; replicate only inside living cells. Cause flu, measles, AIDS. Example: influenza virus (flu).

Fungi

Multicellular; cause athlete's foot, ringworm, candidiasis. Example: Candida albicans (candidiasis).

Parasites

Live on/in host, deriving nutrients at host's expense. Cause malaria, schistosomiasis, hookworm. Example: Plasmodium falciparum (malaria).