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Infectious Diseases
Nature of infectious diseases
Pathogens Infection Disease In order to cause disease, pathogens must
be able toenter, adhere, invade, colonize, and
inflict damage Growth of pathogens or the production of
toxins/enzymes cause disease
Microbes that cause infectious diseases
Bacteria Viruses Fungi Protozoa Helminths Prions
Occurrence of infectious diseases
Epidemiology –study of the occurrence of disease in populations
Disease reservoirs-where the infectious agent survives (humans, rodents) Example = yersinia pestis (plague)
Modes of transmission ingestion, inhalation, casual contact, intimate
contact, bites/animals
History
Emerging infectious diseases-Have not occurred in humans before,Have occurred previously but affected only
small numbers, Or have occurred throughout human
history, but only recently recognized as disease due to infectious agent
Re-emerging infectious diseasesOnce were major health problems globally
or in a particular country, then declined dramatically, but are again becoming health problems for a significant proportion of the population.
The body’s defense mechanisms
First Line of DefenseSkinSecretions Non-specific defenses -
macrophagesNormal Flora
The body’s defense mechanisms
Immune Systemhttp://www.learner.org/channel/courses/biology/archive/animations/hires/a_hiv1_h.htmlHumoral (antibody) response
– B-cells B-cell, plasma cell,
antibodies, memory B-cellsCell-mediated response – T-
cells helper T-cells, killer T-cells,
memory T-cellsVaccination produces
immunity
Prevention
Safewater Purification methods Testing against contamination
Sewage Treatment Waste water plants separate components of
sewage and treat them Chlorination
Food Safety Inspections Pasteurization Regulations
Prevention
Animal Control Domestic inspections Vaccinations Sanitation
Vaccinations Pre-school Threshold proportion Herd immunity
Public Health Organizations
NIH – supports health-related researchCDC – investigates disease outbreaks,
informs the publicFDA – monitors safety of foods and medicinesWHO – coordinates health/vaccine programs
internationally
Treatment
Bacteria (prokaryotes) Antibiotics “destroyer of life” Inhibit cell wall, protein, lipid, or RNA synthesis Penicillin was the first – interfers with cell wall Chloramphenicol, tetracycline – protein synthesis Rifampicin – prevents RNA from being made
Treatment
Viruses Non-living; uses cell materials to replicate Highly toxic to host cells Target virus-specific enzymes involved in making
DNA/RNA Acyclovir – herpes Amantadine – influenza AZT - AIDS
Treatment
Fungi, protozoans, helminths Highly toxic because also eukaryotes Target reproduction, cell membrane, or other
necessary functions Choroquinine - malaria
Resistance
Resistance the ability of the pathogen to survive treatment by a
particular drug Growing problem
Mechanism change in genes that allows them to evade the action of
the drug Stuctural changes in proteins, receptors
Transfer of anti-microbial genes Don’t mutate but acquire it from others Transformation – taking up free-floating DNA plasmids Transduction – virus carries resistant gene to other
bacteria Transposons – small “rogue” sections of DNA Mutations and genetic exchange is rare; but bacterial
growth is high
Bioterrorism
Violent acts or acts dangerous to human life that…appear to be intended:
1. To intimidate or coerce a civilian population; 2. To influence the policy of a government by
intimidation or coercion; or 3. To affect the conduct of a government by
assassination or kidnapping.
Bioterrorism
Biological weapons used in bioterrorism are living microorganisms such as bacteria, viruses, fungi, that can kill or incapacitate.
Health care facilities may be the initial site of recognition and response to bioterrorism activity. Because of this, the names and telephone numbers for internal and external departments or agencies that need to be contacted should be kept by each facility in its bioterrorism readiness plan.
Bioterrorism
Response to bioterrorism agents:Internal reporting requirements (within a
facility): Infection control personnel Epidemiologist (local and state) Administration (health care facility and health
department) Office of public affairs in the health facility
Bioterrorism
External contacts (outside of facility) Local health department State Health Department FBI CDC Local police EMS
Bioterrorism
Agents Bacterial- Anthrax and Plague Viral- Small Pox
Toxins- Botulism and Ricin