Infection facts
• Infection is a host’s response to a pathogen.
• Viruses, bacteria, fungi, and parasites cause infection.
• Infection results when a pathogen enters the body; the pathogen attaches to a cell and destroys the cell’s protective membrane, spreads through blood and lymph, multiplies, and causes infection in target organ or tissue.
Understanding infection
• Results when a host organism responds to a pathogen or disease-causing substance.
• Develops when tissue-destroying microorganisms enter and multiply in the body.
• Takes the form of minor illnesses, such as colds and ear infections, or results in a life-threatening condition called sepsis, which causes widespread vasodilation and multiorgan system failure.
• Caused by four types of microorganisms:
–viruses
–bacteria
–fungi
–parasites.
• Results when a host organism responds to a pathogen or disease-causing substance.
• Develops when tissue-destroying microorganisms enter and multiply in the body.
• Takes the form of minor illnesses, such as colds and ear infections, or results in a life-threatening condition called sepsis, which causes widespread vasodilation and multiorgan system failure.
• Caused by four types of microorganisms:
–viruses
–bacteria
–fungi
–parasites.
How infections develop
Infection occurs when the body’s defense mechanisms break down or when microorganisms override the defense system. Other factors include:
• poor nutrition
• stress
• humidity
• poor sanitation
• crowded living conditions
• pollution
• dust.
Infection results when a pathogen enters the body through direct contact, inhalation, ingestion, or an insect or animal bite.
Infection occurs when the body’s defense mechanisms break down or when microorganisms override the defense system. Other factors include:
• poor nutrition
• stress
• humidity
• poor sanitation
• crowded living conditions
• pollution
• dust.
Infection results when a pathogen enters the body through direct contact, inhalation, ingestion, or an insect or animal bite.
Understanding infectious disorders
• Herpes simplex — virus fuses to host cell membrane, turns off host’s protein synthesis, and replicates; and viral deoxyribonucleic acid is released.
• Herpes zoster — reactivation of varicella-zoster virus; trigger of reactivation unknown.
• Infectious mononucleosis — virus invades B cells of oropharyngeal lymph; B cells die, and virus is released in blood; fever and other symptoms occur.
• Lyme disease — tick injects spirochete into blood or deposits feces on skin; after incubation, spirochetes migrate, cause a rash, and disseminate to other skin areas and organs.
• Rabies — bite transmits virus through skin; the virus replicates and spreads to the spinal cord and brain where it replicates again.
• Respiratory syncytial virus infection — virus transmitted through respiratory secretions; bronchiolitis or pneumonia occurs (severe cases may lead to bronchiolar epithelial damage); and alveolar spaces may fill with fluid.
• Rubella — virus transmitted through body fluid contact; the virus replicates in respiratory tract and spreads to the bloodstream.
• Salmonellosis — a gram negative bacilli that is ingested through contaminated food or water, or through contact with an infected person or animal; the bacilli then invades the upper small bowel and causes bacteremia.
• Toxoplasmosis — intracellular parasites are ingested; parasites are then released and invade and multiply in the GI tract; the parasitic cell ruptures host and disseminates throughout the body.
• Herpes simplex — virus fuses to host cell membrane, turns off host’s protein synthesis, and replicates; and viral deoxyribonucleic acid is released.
• Herpes zoster — reactivation of varicella-zoster virus; trigger of reactivation unknown.
• Infectious mononucleosis — virus invades B cells of oropharyngeal lymph; B cells die, and virus is released in blood; fever and other symptoms occur.
• Lyme disease — tick injects spirochete into blood or deposits feces on skin; after incubation, spirochetes migrate, cause a rash, and disseminate to other skin areas and organs.
• Rabies — bite transmits virus through skin; the virus replicates and spreads to the spinal cord and brain where it replicates again.
• Respiratory syncytial virus infection — virus transmitted through respiratory secretions; bronchiolitis or pneumonia occurs (severe cases may lead to bronchiolar epithelial damage); and alveolar spaces may fill with fluid.
• Rubella — virus transmitted through body fluid contact; the virus replicates in respiratory tract and spreads to the bloodstream.
• Salmonellosis — a gram negative bacilli that is ingested through contaminated food or water, or through contact with an infected person or animal; the bacilli then invades the upper small bowel and causes bacteremia.
• Toxoplasmosis — intracellular parasites are ingested; parasites are then released and invade and multiply in the GI tract; the parasitic cell ruptures host and disseminates throughout the body.
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