Small pox and chicken pox

A primer on small pox and chicken pox infections

1. Pox (small, chicken) Dr. S. A. Rizwan M.D., Assistant Professor, Dept. of Community Medicine, VMCHRI, Madurai.

2. Learning objectives At the end of this lecture you sh be able to Describe the epidemiological triad and the prevention aspects of these infections Understand the factors that contribute to epidemics Enumerate the factors that led to eradication of small pox Enumerate the differences between the two

3. Small pox பெரியம்மை

4. Introduction Smallpox is a serious, contagious and sometimes fatal disease At its height, 10-15 million cases a year, with 2 million deaths There is no specific treatment for smallpox, and the only prevention is vaccination . The name smallpox is derived from the Latin word “ spotted ” and refers to the raised bumps that appear on the face and body of an infected person . It is caused by variola virus, Orthopoxvirus genus

5. History Mummified remains of Ramses. (1157 B.C.) Smallpox was likely carried from Egyptian traders to India By 1967 it became a major killer in not less than 33 countries Those who survive became immune As a result, physicians intentionally infected healthy persons with smallpox organisms

6. Variolation It is the act of taking samples (pus from pustules or ground scabs) from patients whose disease had been benign, and introducing it into others through the nose or skin

7. Edward Jenner

8. Jenner’s contribution He found that, the cowpox would protect the patient from smallpox He proposed it in 1798 In England vaccination with cowpox became compulsory in 1853 Jenner was honored for his technique, and ‘Vaccine’ became the universally used term to indicate introducing material under the skin to produce a protection against disease

9. Variola virus

10. Transmission Humans are the only natural host of smallpox (no animal reservoir) Transmission generally occurs from direct and fairly prolonged face-to-face contact Infected aerosols and air droplets spread in face-to-face contact

11. Pathogenesis P ortal of entry: respiratory tract or inoculation on skin Source of infection: Excretions from the mouth and nose, rather than scabs During incubation the virus proceeds through infection, replication, and liberation (usually accompanied by cell necrosis) first at the site of inoculation and then to the regional lymph nodes, then deeper lymph nodes and bloodstream

12. Pathogenesis 4 orthopoxviruses are known to infect humans: variola , vaccinia , cowpox, and monkeypox Variola major is severe and the most common form with more extensive rash and higher fever with a death rate of 30% Variola minor has less common presentation and much less severe with death rate of 1%

13. Pathogenesis Variola Major has 3 clinical presentations based on the nature and evolution of the lesions: Ordinary : most frequent, corresponds to classical description Modified : milder and may occur in previously vaccinated people; rarely fatal Flat and Hemorrhagic : very severe but uncommon

14. Stages of Smallpox Incubation Period 12-14 days, person is not contagious Prodrome Phase Begins abruptly with fever, malaise, headache, head and body aches, prostration, and often nausea and vomiting Body temperature rises to at least 101 F and is often higher When the first visible lesions appear the fever may start to go down - most contagious period Rash emerges as small red spots on tongue and in mouth (about 24 hours before the appearance of rash on the skin) Lesions in the mouth and pharynx enlarge and ulcerate quickly, releasing large amount of virus into the saliva

15. Stages: Rash Phase Centrifugal distribution P alms and soles are involved lesions are all in the same stage of development on that part of the body (unlike chickenpox)

16. Outcomes of infection Those who survive usually have scars In eye involvement, blindness could occur Recovery results in long lasting immunity N o evidence of chronic or recurrent infection

17. Vaccination L ive vaccinia virus A dministered using a bifurcated needle, not an injection B ifurcated needle is dipped into the vaccine and then used to prick the skin 15 times in about 3 seconds in a 5mm radius area A dministered into the superficial layer of the skin

18. Course of vaccination If vaccination is successful a red, itchy bump develops at the vaccine site in 3-4 days; a papule surrounded by erythema In the first week the bump becomes a blister, fills with pus, and begins to drain During the second week the blister begins to dry and a scab forms; the scab then falls off leaving a scar It is given on the right side universally

19. A reminder of the small pox era

20. Control Only after WWI most of Europe become smallpox free, and only after WWII transmission stopped throughout Europe and North America In developing countries smallpox continued largely unabated until middle of 20 th century

21. Control 1958: Soviet Union proposed to the WHO that a global smallpox eradication program be undertaken The campaign was based on a two fold strategy 1. Mass vaccination campaigns in each country using a vaccine of ensured potency and stability that would reach at least 80% of the population 2. Surveillance-Containment - isolation of patients and the vaccination of family members and other contacts in the immediate vicinity

22. Control Ring vaccination: I ncorporated into the current CDC Smallpox Plan The strategy involves the following steps: Rapid identification and isolation of all smallpox cases Identification and vaccination of contacts of smallpox cases Monitoring contacts for development of fever and isolating them if fever occurs Vaccination of household members of contacts if no contraindications to vaccination exist

23. Management of an outbreak Surveillance is easier because of the distinctive rash Containment involves efficient detection of cases and identification and vaccination of contacts Patients diagnosed with smallpox should be physically isolated All specimen collectors, care givers and attendants coming into close contact with patients should be vaccinated Medical care givers, attendants, and mortuary workers should wear gloves, caps, gowns, and surgical masks

24. Management of an outbreak Contaminated clothing and bedding, if not incinerated, should be autoclaved or washed in hot water containing bleach Fumigation of premises with formaldehyde Airborne and Contact Precautions in addition to Standard Precautions should be implemented for patients with suspected smallpox

25. Eradication In India Last case reported on 17 th May 1975 in Bihar On 24 th May 1975, imported from Bangladesh In April 1977 declared free from smallpox

26. Eradication 26 th October 1977 the last naturally occurring case of smallpox was recorded in Somalia In 1978 two cases were reported. These were both from people working in labs with smallpox in England 8 th May 1980, WHO declared that smallpox has been eradicated

27. Factors that led to eradication Epidemiological factors: N o known animal reservoir N o long-term carrier of the virus L ife-long immunity after recovery from the disease D etection of cases, the rash was so characteristic Sub-clinical infection did not transmit the disease V accine highly effective I nternational co-operation

28. Chicken POX சின்னம்மை

29. Introduction A cute, highly infectious disease caused by Varicella-Zoster (V–Z) virus Chicken pecked skin appearance, chickpea appearance World-wide in distribution and occurs in endemic and epidemic forms Chickenpox and Herpes zoster as different host responses to the same etiological agent In India, approx. 28,000 cases per year

30. Epidemiological determinants Agent: Human (alpha) herpes virus Primary infection causes chicken pox Recovery followed by latent infection Reactivation results in zoster- a painful, vesicular, pustular eruption in distribution of one or more sensory nerve roots Can be grown in tissue culture Incubation period: 14-16 days (7-21 days)

31. Source of infection Usually a case of chicken pox Virus present in oropharyngeal secretions and lesions of skin and mucosa Rarely may be a patient with herpes zoster It can be isolated from the vesicular fluid during the first 3 days of illness

32. Infectivity Period of communicability: 1-2 days before the appearance of rash, and 4-5 days thereafter It tends to die out before the pustular stage Patient ceases to be infectious once the lesion have crusted Secondary attack rate: About 90% in household contacts

33. Host factors Age Children under 10 years of age Few escape until adulthood but can be severe in adults Immunity One attack give durable immunity Maternal antibody protects the infant for few months No age is exempt in the absence of immunity IgG antibodies persist for life and correlate with protection Cell mediated immunity is important in recovery Pregnancy: Risk for fetus and neonate

34. Environmental factors It shows a seasonal trend, occurring mostly during the first six months of the year Overcrowding In temperate climates, there is little evidence of seasonal trend

35. Transmission Droplet infection and droplet nuclei ‘Face to face’ (personal) contact Portal of entry: respiratory tract Virus is extremely labile, so fomites unlikely to transmit Contact infection plays a significant role when an individual with herpes is an index case Congenital varicella - it crosses the placental barrier and infects the foetus

36. Clinical features Clinical spectrum Mild illness with few scattered lesions S evere febrile illness with widespread rash Pre-eruptive stage Sudden onset with mild to moderate fever Pain in the back, shivering and malaise Duration about 24 hours In adults, prodromal illness is usually more severe and may last for 2-3 days before the rash

37. Clinical features Eruptive stage: in children the rash comes on day the fever starts and first sign The distinctive features of rash are Rash is symmetrical Appears on the trunk and then comes to face, arms ,legs Mucosal surfaces (buccal, pharyngeal) are involved Axilla affected. Palms and soles usually not involved The density of eruption diminishes centrifugally Pleomorphism - All stages of rash (papules, vesicles and crusts) may be seen simultaneously in the same area

38. Clinical features E volution of rashes The rash advances quickly through the stages of- macule  papule  vesicle  scab Vesicles filled with clear fluid resembling ‘dew-drops’ Superficial in site, with easily ruptured walls and surrounded by an area of inflammation Vesicles may form crusts directly. Many lesions may abort Scabbing begins 4-7 days after the rash appears Fever not high but exacerbations with fresh crop

39. Complications It’s a mild, self-limiting disease Patients at risk of complications are Immunosuppressive patients Cancer patients Recipients of organ transplants Chemo, radio, steroid therapy recipients HIV infected Children with leukemia

40. Complications Haemorrhages (varicella haemorrhagica ) Pneumonia Encephalitis Acute cerebellar ataxia Reye’s syndrome Maternal varicella may cause foetal wastage & birth defects Acute retinal necrosis Secondary bacterial infections (Cellulitis , erysipelas, epiglottitis, osteomyelitis, scarlet fever and meningitis) Pitted scars

41. Congenital defects in babies Damage to brain: encephalitis, microcephaly, hydrocephaly, aplasia of brain Damage to the eye: microphthalmia , cataracts, chorioretinitis , optic atrophy Other neurological disorder: damage to cervical and lumbosacral spinal cord, motor/sensory deficits, absent deep tendon reflexes, anisocoria /Horner's syndrome Damage to body: hypoplasia of upper/lower extremities, anal and bladder sphincter dysfunction Skin disorders: (cicatricial) skin lesions, hypo pigmentation

42. Laboratory diagnosis Most rapid and sensitive Examination of vesicle fluid under electron microscope Round particles which may be used for cultivation Scrapings of floor of vesicles show multinucleated giant cells coloured by Giemsa stain Serology for epidemiological surveys

43. Control No specific treatment for chicken pox Notification Isolation of cases for about 6 days after onset of rash Disinfection of articles soiled by nose and throat discharges Antiviral drugs provide effective therapy for varicella (acyclovir , valaciclovir , famiciclovir and foscarnet )

44. Prevention Varicella zoster immunoglobulin (VZIG) VZIG given within 72 hours of exposure has been recommended for prevention Dosage: 1.25-5ml intramuscularly Used for immunosuppressed contacts of acute cases or newborn contacts P rovide improvement in high risk children with varicella

45. Vaccine L ive attenuated vaccine (Japan) M ild local reaction at inoculation site is 1 % A general reaction mainly rash or mild varicella may occur Seroconversion in healthy seronegative children is over 90 % Age shift of peak incidence due to vaccinations is a major concern

46. Vaccine Monovalent vaccine One or two dose schedule (0.5 ml subcutaneous injection) For children between 12-18 months Two dose schedule for persons aged >13 years Minimum interval between doses 6 weeks Combination vaccines (MMRV) for children 9 months to 12 years Duration of immunity probably 10 years

47. Difference between pox (small, chicken)

48. Difference between small pox and chicken pox Small pox Chicken pox Incubation 12 days (7-17) 15 days (7-21) Prodromal Severe Mild Distribution of rash Centrifugal Centripetal Palms and soles involved Not involved Axilla free Axilla affected Extensor surfaces Flexor surfaces Characteristics of rash Deep seated Superficial Multilocular , umbilicated Unilocular , dew drop One stage at a time Pleomorphic No inflammation around the vesicles Inflammation seen

49. Difference between small pox and chicken pox Small pox Chicken pox Evolution of rash Slow and majesti c, passing through definite stages of macule, papule, vesicle and pustule Very rapid Scabs 10-14 days Scabs in 4-7 days Fever Subsides with appearance of rash, may rise again at the pustular stage Fever appears with each fresh crop of rash

50. Review 1 Infectivity of chicken pox lasts for Till the last scab falls off 6 days after onset of rash 3 days after onset of rash Till fever subsides

51. Review 2 Chicken pox is characterized by all except Scabs are infective Pleomorphic stages Rashes symmetrical centripetal dew drop like Palms and soles not affected by rash

52. Review 3 Small pox eradication was successful due to all of the following reasons except Subclinical cases did not transmit the disease A highly effective vaccine was available Infection provided lifelong immunity Cross resistance existed with animal pox

53. Review 4 A ll of the following are true about varicella virus except 10-30% chance of recurrence All stages of rash seen at the same time Secondary attack rate is 90% Rash commonly seen in flexor area

54. Review 5 A ll of the following are true about varicella virus except Lesions appear in crops Centripetal distribution of rashes Rashes shows rapid progression from macule to vesicle Crusts contain live virus

55. Review 6 What is the difference between vaccination and variolation ?

56. Review 7 When was the last case of small pox in India identified and when was it declared small pox free?

57. Review 8 When was the world declared free of small pox?

58. Review 9 Why is small pox called class blind?

59. Review 10 Can small pox infection occur in the world today? If yes, what will be the consequences?

60. Thank you