Final answer:
Blood-borne invasion occurs through direct introduction of pathogens into the bloodstream or by stealth tactics where pathogens invade and reproduce within immune cells. These invasions can happen through contaminated medical instruments, wounds, or contact with infected fluids. Pathogens must evade the immune system to survive and disseminate within the host.
Step-by-step explanation:
There are two main ways that blood-borne invasion can take place:
- Direct introduction of pathogens into the bloodstream through an external means, such as contaminated catheters, dental procedures, piercings, wounds, or intravaginal products. This also includes contact with infected body fluids, for instance, through IV drug use, sexual transmission, or healthcare workers treating patients.
- The use of stealth tactics by microorganisms, allowing them to invade host cells, evade the immune system, and disseminate through blood-sucking insects. Stealth pathogens can infect and reproduce inside blood cells or other cells of the immune system to spread to parts of the body with poor immune surveillance, effectively evading or subverting the innate or adaptive responses of the host.
To survive in blood, pathogens must evade phagocytic cells that are part of the immune response. Pathogens can accomplish this by infecting and reproducing within these cells, a form of stealth pathogenesis. Alternatively, introducing pathogens during events of breached barriers (e.g., cuts, surgeries, or via the use of tampons) can lead to a direct invasion of the bloodstream.