The document discusses infectious diseases, which are clinically evident illnesses caused by pathogenic agents like viruses, bacteria, fungi, or parasites. These diseases can be transmitted between individuals through various pathways like physical contact or contaminated objects. Non-infectious diseases are also discussed, which are not caused by pathogens and cannot be transmitted between people. They may be due to genetic, environmental, or lifestyle factors.

1. Infectious Disease This false-colored electron micrograph shows a malaria sporozoite migrating through the midget epithelia.

5. primary pathogen Organisms which cause an infectious disease in a host with depressed resistance are classified as opportunistic pathogens . Opportunistic disease may be caused by microbes that are ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract, and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridium difficult colitis) or from the environment as a result of traumatic introduction (as in surgical wound infections or compound fractures).

7. AIDS AIDS Virus Malaria mosquito

11. Virus Aids Virus Rabies Virus

12. Conserve RNA SARS Mycobacterium tuberculosis Bluetongue Virus

16. Human cancer virus Prostate-Cancer

17. breast cancer