Infectious Diseases

1. Infectious Diseases Analyze issues of public health, infectious diseases, and bioterrorism.

2. Nature of infectious diseases • Pathogens-microorganisms that are capable of causing disease • Infection-results when a pathogen invades and begins growing within the host • Disease-results only if and when tissue function is impaired (i.e. burns, skin lesions) • The body has defense mechanisms to prevent infection • In order to cause disease, pathogens must be able to enter, adhere, invade, colonize, and inflict damage • Entrance to the host-mouth, eyes, genital openings, wounds • Growth of pathogens or the production of toxins/enzymes cause disease • Some normal flora prevent diseases

3. Microbes that cause infectious diseases • Bacteria-Salmonella typhi, Staphylococcus aureus • Viruses-apart from the host cell, have no metabolism and cannot reproduce • Fungi-form spores • Protozoa-acquired through contaminated food or water, or bite of an arthropod (mosquito) • Helminths-simple, invertebrate animals, some infectious parasites – symptoms: abd. pain and diarrhea • Prions-Creutzfeldt-Jakob disease

4. 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 • Modes of transmission

5. Host defenses against infectious diseases • Nonspecific mechanisms are the body’s primary defense against disease-anatomical barriers, physiological deterrents and presence of normal flora (skin, low pH and high salinity) • Specific mechanisms-immunity • Vaccination-produces immunity

6. Analyze the role of public health in the prevention of infectious diseases.

7. Public health measures toward prevention • Safe water-US water is purified through settling, filtration, and chlorination • Sewage treatment and disposal is mandated by US government • Food safety-US has many standards, inspection plans and regulations dealing food preparation, handling, and distribution • Animal control programs-Domestic herds are inspected, rabid animals are destroyed, rat control programs in place in urban areas • Vaccination programs mandate that children be vaccinated prior to • school • Pesticides to block vector-borne disease – those carried by mosquitoes

8. Public health organizations enforce regulation, provide public health services • National Institutes of Health (NIH)-supports health-related research • Centers for Disease Control (CDC)-investigates disease outbreaks, publishes reports, sponsors education/ research, reference labs • Food and Drug Administration (FDA)-monitors safety of food, medicines and other products • World Health Organization (WHO)-provides international surveillance and control of disease

9. Benefits of public health research • New research techniques-rapid identification • HIV protease inhibitors • Vaccine research • Identification of better preventative measures

10. Investigate the treatment of infectious diseases

11. Drugs used to treatment of bacterial diseases can be grouped into categories based on their modes of action • Penicillins/cephalosporins interfere with certain layers of cell wall • Chloramphenicol, tetracyclines, erythromycins-may be toxic when used in high doses or prolonged periods of time • Rifampin-used for treatment of TB

12. Drugs that effectively inhibit viral infections are highly toxic to host cells because viruses use the host’s metabolic enzymes in reproduction • Antiviral drugs target virus-specific enzymes • Acyclovir-used in treatment of genital herpes • Amantadine-used to prevent or moderate influenza • AZT-inhibit replication of HIV genome

13. Development of drugs used to treat fungal, protozoan, and helminthic diseases are also highly toxic to mammals • Azole derivatives inhibit sterol synthesis • Amphotericin B-disrupts cell membrane

14. Antimicrobial resistance presents ongoing problems in the fight against infectious diseases • Penicillin resistance noted as early as 1943 • Mycobacterium tuberculosis-some strains resistant to all drugs • Resistance to antibiotics-result of changes in genetic information

15. Analyze emerging and re-emerging infectious diseases

16. * Globally, infectious diseases remain the leading cause of death, and they are the 3rd leading cause of death in the US

17. 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 • Examples and contributing factors

18. 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. • Examples and contributing factors

19. Examine the containment of bioterrorism agents

20. Agents Bacterial – Anthrax and Plague • Viral - Smallbox • Toxins – Botulism and Ricin

21. Containment of bioterrorism agents • Terrorism is defined in the United States Code, Title 18, section 2331(18 USC 2331) as “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.

22. Biological weapons used in bioterrorism are living microorganisms such as bacteria, viruses, fungi, that can kill or incapacitate.

23. 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.

24. Response to bioterrorism agents: • 1. 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

25. 2. External contacts (outside of facility) • Local health department • State Health Department • FBI • CDC • Local police • EMS

26. Agents • Bacterial- Anthrax and Plague • Viral- Small Pox • Toxins- Botulism and Ricin

27. Anthrax • Acute infectious disease caused by bacillus anthracis. • Infections in humans:   • Skin contact – cutaneous, ingestion-gastrointestinal, inhalation-pumonary  • Person-to-person transmission of inhalation disease does not occur. *  • *direct exposure to vesicle secretions of cutaneous anthrax can result in a secondary infection.

28. Anthrax • Pulmonary signs and symptoms: • Flu-like symptoms that may briefly improve two to four days after initial symptoms • Abrupt onset of respiratory failure • Hemodynamic collapse • Thoracic edema • Widened mediastinum on xray • Positive blood culture in 2-3 days of illness • Prognosis:  • Good if treated early. Increased mortality rate if treated after respiratory onset.

29. Anthrax • Cutaneous signs and symptoms: • Local skin involvement with direct contact • Commonly seen on head, forearms, or hands • Localized itching followed by popular lesion that turns vescular within 2-6 days – develops into depressed black eschar • Prognosis: • Good if treated with antibiotics.

30. Gastrointestinal signs and symptoms: • Abdominal pain, nausea, vomiting, fever • Bloody diarrhea, hematemesis • Positive culture after 2-3 days • Prognosis: • If progression to toxemia and sepsis, prognosis is poor.

31. Anthrax • Modes of transmission:  • Inhalation of spores • Skin contact • Ingestion of contaminated food  • Incubation period:  • Pulmonary: 2-60 days • Cutaneous: 1-7 days • Gastrointestinal: 1-7 days 

32. Anthrax • Transmission:  • Anthrax is not airborne person to person. Direct contact with infectious skin lesions can transmit infection. • Prevention: • Vaccine available-limited quantities.

33. Botulism • Potent neurotoxin caused by an anaerobic bacillus- colstridium botulinum. • Transmission: • Contaminated food • Inhalation • Signs and symptoms: •   Gastrointestinal symptoms • Drooping eyelids • Weakened jaw clench • Difficulty swallowing or speaking • Blurred vision • Respiratory distress

34. Botulism • Incubation period:  • Neurological SxS for food borne botulism – 12-36 hours after ingestion • Neurological SxS for inhalation botulism – 24-72 hours after exposure  • Prevention: Vaccine available • Botulism cannot be transmitted person to person.

35. Plague • Plague is an acute bacterial disease caused by yersinia pestis. • Signs and Symptoms: •  Fever • Cough • Chest pain • Hemoptysis • Watery sputum • Bronchopneumonia on xray

36. Plague • Mode of Transmission:  • Plague normally transmitted from an infected flea • Can be aerosol-probable use in bioterrorism • Can be transmitted person to person • Incubation period: •   Flea bite – 2-8 days • Aerosol – 1-3 days • Prognosis: Good if treated with antibiotics early.

37. Ricin • Ricin is a potent protein toxin derived from Castor beans. Castor beans are found easily all over the world and the toxin is fairly easily produced. For this reason ricin could be used as a biological weapon with relative ease. • Infections in Humans • Aerosol • Ingestion

38. Ricin • Signs and Symptoms: • 18-24 hours Weakness • Fever • Cough • Pulmonary edema • 36-72 hours • Severe respiratory distress • Death from hypoxemia

39. RICIN • Incubation period: • 8-18 hours • Prognosis: • Poor-no vaccine available • Ricin does not spread easily person to person.

40. Smallpox • Smallpox is an acute viral illness caused by the variola virus. • Mode of transmission: Airborne: droplets • Signs and symptoms: • Flu like symptoms-fever, myalgia • Skin lesions appear quickly progressing from macules to papules to vesicles • Rash scabs over in 1-2 weeks • Rash occurs in all areas at once, not in crops

41. Smallpox • Incubation period: • From 7 to17 days, average is 12 days • Contagious when the rash is apparent and remains infectious until scabs separate (approx. 3 weeks)

42. Smallpox • Prognosis: • Vaccine available and effective post-exposure • Passive immunization is also available in the form of vaccina- immune-globulin (Vig) • Smallpox has a high mortality rate.