Infectious Diseases

Nature of infectious diseases Pathogens Infection Disease In order to cause disease, pathogens must be able to enter, 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

Picture of Health??

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 diseases Once 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.

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 Pre-school Threshold proportion Herd immunity

Public Health Organizations NIH – supports health-related research CDC – investigates disease outbreaks, informs the public FDA – monitors safety of foods and medicines WHO – 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

The body’s defense mechanisms First Line of Defense Skin Secretions Non-specific defenses - macrophages Normal Flora

The body’s defense mechanisms Immune System http://highered.mheducation.com/sites/0072507470/student_view0/chapter22/animation__the_immune_response.html Humoral (antibody) response – B-cells B-cell, plasma cell, antibodies, memory B-cells Cell-mediated response – T-cells helper T-cells, killer T-cells, memory T-cells Vaccination produces immunity An inside look at the flu

Need for Vaccines Spanish flu killed millions during WWI Still kills today but generally in the 100s Endemic – local, normal, baseline disease Epidemic – widespread and in large numbers at same time Pandemic – world-wide Protects individual Lowering occurrence in population can protect those who can’t get vaccine (herd immunity) Threshold response - percent of people who need to be vaccinated for herd immunity to work

Types of vaccinations Live but weakened disease agents Good but higher mutations, can cause illness, refrigeration Inactivated or killed disease agents Less effective but safer, need boosters Subunit vaccines – use only subunits of antigens Toxoid vaccines - against toxins made by bacteria Conjugate vaccines – helps infants recognize antigens DNA vaccines Recombinant vector vaccines

Vaccine Production Tested in cells and in animals Eggs – virus injected into fertilized eggs to reproduce and then protein coats isolated and tested; takes up t0 6 months Cell Culture – grown in confined cells; cells die and viral coats are isolated and tested, quicker Pharming - tobacco plant infected with Agrobacterium that has gene for viral coat antigen inserted; virus-like particles of protein then isolated; no DNA so more safety.

Issues with Vaccines Public perception Challenges Myths (autism) Makes me sick or allergies Government intrusion Religious freedom Challenges Speed of production Safety and stability Storage and distribution Changing pathogen landscape

Bioterrorism Violent acts or acts dangerous to human life that…appear to be intended: To intimidate or coerce a civilian population; To influence the policy of a government by intimidation or coercion; or 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 Toxins- Botulism and Ricin Bacterial- Anthrax and Plague Viral- Small Pox Toxins- Botulism and Ricin