Viruses

1. Viruses

2. Smallpox

3. The Year Was 1777 • It was a bold executive decision. Faced with a bio-terrorist threat, the commander in chief issued an order that every soldier be inoculated against smallpox, despite serious concerns about the medical risks involved. • The Commander in Chief of the Continental Army was George Washington.

4. Hearing of possible enemy plans to infect his troops with the dreaded smallpox virus, the future president had all recruits to his ragtag army “vaccinated” with infected material • This was especially daring because it was during the period that the church was condemning innoculation.

5. Washington’s call proved to be right. He subsequently lost no soldiers in the great smallpox epidemic that swept the Colonies, and indeed some historians believe this decision in large part determined the outcome of the War of Independence.

6. The distribution of the smallpox rash is usually similar to that shown here. It is most dense on the face, arms and hands, legs and feet. The trunk has fewer pocks than the extremities.

12. Smallpox on Infant

14. Smallpox • Believed to have originated over 3,000 years ago in India or Egypt • Considered to be one of the most devastating diseases known to humanity.

15. In some ancient cultures, smallpox was such a major killer of infants that custom forbade the naming of a newborn until the infant had caught the disease and proved it would survive.

16. Fatal Infectious Disease (severe rash which leaves scars, fever, headache, vomiting and diarrhea. ) • No Treatment / No Cure • Vaccination Available • Direct Person-to- Person Contact • Used in Biological Warfare during • French and Indian War

17. In 1763 Sir Jeffrey Amhurst, commander in chief of the British forces fighting a North American Indian uprising west of the Allegheny mountains, wrote to Colonel Bouquet: "Could it not be contrived to send the Smallpox among those disaffected tribes of Indians?" • Bouquet replied: "I shall try and inoculate them with some blankets, and take care not to get the disease myself.

19. Smallpox Cycle • The rash appears 2 to 4 days after the patient first becomes ill with fever

20. Smallpox Cycle • On the second day of rash, more papules appear. Although they differ somewhat in size, note that they all have a very similar appearance.

21. Smallpox Cycle • By day 3, the rash has become more distinct and raised above the skin surface. Fluid is accumulating in the papules to form vesicles.

22. Smallpox Cycle • By day 4, the vesicles are more distinct. Although they contain fluid, they feel very firm to the touch. When broken, they do not collapse because the fluid is contained in many small compartments.

23. Smallpox Cycle • By day 5, the fluid in the vesicles has become cloudy and looks like pus. At this stage, the pocks are called pustules. At this time, the fever usually rises and the patient feels more ill than before.

24. Smallpox Cycle • On day 7, the rash is definitely pustular. Note that the pocks, although varying somewhat in size, all resemble each other in appearance. The rash is now so characteristic that there should be no mistake in diagnosis.

25. Smallpox Cycle • During days 8 and 9, the pustules increase somewhat in size. They are firm to the touch and deeply embedded in the skin.

28. Smallpox Cycle Gradually the pustules dry up and dark scabs form. The scabs begin to appear between 10 and 14 days after the rash first develops. The scabs contain live smallpox virus. Until all scabs have fallen off, the patient may infect others.

29. Smallpox Cycle • By day 20, the scabs have come off and light-coloured or depigmented areas are observed. The skin seldom returns to its normal appearance. Scars which last for life, often remain (especially on the face). Such scars are an indication of previous infection with smallpox.

30. Smallpox had two main forms: • Variola Major • Variola Minor. • The two forms showed similar lesions. The disease followed a milder course in variola minor, which had a case-fatality rate of less than 1%. • The fatality rate of variola major was around 30%.

31. There are two rare forms of smallpox: • Hemorrhagic • Malignant. • Hemorrhagic is invariably fatal, the rash is accompanied by hemorrhage into the mucous membranes and the skin.

32. Malignant smallpox is characterized by lesions that did not develop to the pustular stage but remained soft and flat. • It was almost invariably fatal.

33. Smallpox is transmitted from person to person by infected aerosols and air droplets spread in face-to-face contact with an infected person after fever has begun, especially if symptoms include coughing.

34. The disease can also be transmitted by contaminated clothes and bedding, though the risk of infection from this source is much lower. • Ro = 5 to 7 from an Index Case

35. Ro = Reproductive Ratio • When • Ro < 1 • the infection will die out in the long run (provided infection rates are constant). But if • Ro > 1 • the infection will be able to spread in a population. Large values of R0 may indicate the possibility of a major epidemic.

36. Values of R0 of well-known infectious diseases Desease Mode of Transmission Ro Measles Airborne 12–18 Pertussis Airborne droplet 12–17 Diphtheria Saliva 6–7 Smallpox Social contact 5–7 Polio Fecal-oral route 5–7 Rubella Airborne droplet 5–7 Mumps Airborne droplet 4–7 HIV/AIDS Sexual contact 2–5 SARS Airborne droplet 2–5 Influenza (1918 Strain) Airborne droplet 2-3

37. Smallpox Vaccine • Edward Jenner's demonstration, in 1798, that inoculation with cowpox could protect against smallpox brought the first hope that the disease could be controlled.

38. “Pox Type” Virus • Live Virus Vaccine • Reactions Vary to Vaccine • 15-52 Persons Experience Severe Reactions • 1-2 People will Die • Bifurcated (Two-Pronged) Needle

42. Accidental auto-inoculation of cheek with vaccine virus, approximately 5 days old. Primary take on arm, 10-12 days old.

43. Accidental auto-inoculation of eyelid with vaccine virus

44. West Nile Virus

45. West Nile virus was first isolated from a febrile adult woman in the West Nile District of Uganda in 1937.

46. WNV • Mosquito-borne Virus • Causes Encephalitis or Meningitis • Bird  Mosquito  Horse or Man • No Treatment • No Human Vaccine • 1% Case Fatality Rate • Epidemiologists Use Sentential Surveillance

47. Transmission Cycle of West Nile Virus Horses and Humans are Accidental Dead End Hosts Mosquito to Bird Bird to Mosquito

50. 1999 – 25 Cases