Monday 10 March 2014

The course of infection, symptoms and transmission of pulmonary tuberculosis.

Transmission

Mycobacterium tuberculosis and Mycobacterium bovis are bacteria that causes tuberculosis; it transmitted in aerosol (air born droplets) so can be transmitted by coughing, sneezing and spitting- providing some cells are breathed in. It can also be contracted from cows milk.

Risk of infection is increased by:
  • Over crowded conditions
  • Weak immune system
  • Repeated contact with infect people
Course of infection

Primary infection:
  • Bacteria enter the lungs and begin to multiply
  • White blood cells go to attack them (engulfed by phagocytes) (encased in tubercle by macrophages)
  • This inflames lymph nodes so they can't drain the lungs (causing cough)
  • Often at this stage most bacteria are destroyed, but some may remain (dormant)
Post-primary infection:
  • Years later the remaining bacteria cause a second infection (if immunosuppressed)
  • They attack the epithelial cells- causing the infected person to cough it up damaged lung tissue
  • The damage allows bacteria to enter the blood and spread to other organs
  • The damage decreases the available surface area for gas exchange and makes the diffusion distance further, meaning sufferers will have reduced gas exchange
Symptoms
  • Cough
  • Fever
  • Fatigue

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