Epidemiology of Measles

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Epidemiology of Measles

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1. Epidemiology of Measles Prof. Ashry Gad Mohamed Prof. of Epidemiology

2. Highly contagious viral illness First described in 7th century Near universal infection of childhood in prevaccination era Common and often fatal in developing areas


4. Cases 2005 . An estimated 345 000 people, the majority of them children, died from measles in 2005. From 2000 to 2005, more than 360 million children globally received measles vaccine.

5. Global Progress Measles Mortality Reduction by 50% by 2005 (compared to 1999 : 875,000 deaths)

6. Deaths from Measles Africa 126 000 [93 000 - 164 000] Americas <1 000 [-] Eastern Mediterranean 39 000 [26 000 - 53 000] European <1 000 [-] South-East Asia 174 000 [126 000 - 233 000] Western Pacific 5000 [3000 - 8000] TOTAL 345 000 [247 000 - 458 000]

9. Percent reduction in estimated measles deaths by WHO region between 1999 and 2002

10. Measles Case Counts and Coverage Saudi Arabia 1983-2004

11. There was a marked reduction in the epidemic peak from 500/100 000 in the 1970s to < 80/100 000 in the 1990s. Incidence among children 6–8 months of age fell from > 400/100 000 before the implementation of the new policy to < 100/ 100 000 in 1997. Similarly, among children aged 9–11 months, the number of cases fell from > 200/100 000 before the implementation of the new policy to <100/100 000 in 1997. 2005 373cases

12. Measles Pathogenesis Respiratory transmission of virus Replication in nasopharynx and regional lymph nodes Primary viremia 2-3 days after exposure Secondary viremia 5-7 days after exposure with spread to tissues

13. Measles Clinical Features Incubation period 10-12 days Stepwise increase in fever to 103°F or higher Cough, coryza, conjunctivitis , malaise, sneezing, rhinitis, congestion Koplik spots

15. Measles Clinical Features 2-4 days after prodrome, 14 days after exposure Maculopapular, becomes confluent Begins on face and head Persists 5-6 days Fades in order of appearance

18. Condition Diarrhea Otitis media Pneumonia Encephalitis Hospitalization Death Measles Complications

19. Measles Complications by Age Group

20. Measles Clinical Case Definition Generalized rash lasting >3 days, and Temperature 101°F (>38.3°C), and Cough or coryza or conjunctivitis

21. Measles Laboratory Diagnosis Isolation of measles virus from a clinical specimen (e.g., nasopharynx, urine) Significant rise in measles IgG by any standard serologic assay (e.g., EIA, HA) Positive serologic test for measles IgM antibody

22. Measles Virus Paramyxovirus (RNA) One antigenic type Rapidly inactivated by heat and light

23. Reservoir Human Incubation period. Clinical case No animal reservoir

24. Transmission The virus spreads by the respiratory route via aerosol droplets and respiratory secretions which can remain infectious for several hours. The infection is acquired through the upper respiratory tract or conjunctiva

25. In the pre-vaccination era, the maximum incidence was seen in children aged 5 - 9 years. By the age of 20, approximately 99% of subjects have been exposed to the virus. With the introduction of vaccine, measles infection has shifted to the teens in countries with an efficient programme.

26. In contrast, in third world countries, measles infection has its greatest incidence in children under 2 years of age. the disease is a serious problem with a high mortality (10%) with malnutrition being an important factor in developing countries In general measles mortality is highest in children < 2 years and in adults

27. Temporal pattern Peak in late winter–spring Communicability 4 days before to 4 days after rash onset.

30. Measles Vaccines

31. Measles Vaccine Composition Live virus Efficacy 95% (range, 90%-98%) Duration of Immunity Lifelong Schedule 2 doses Should be administered with mumps and rubella as MMR The seroconversion rate is 95% and the immunity lasts for at least 10 years or more, possibly lifelong

32. MMRV (ProQuad) Combination measles, mumps, rubella and varicella vaccine Approved children 12 months through 12 years of age (up to age 13 years) Titer of varicella vaccine virus in MMRV is more than 7 times higher than standard varicella vaccine

33. MMR Vaccine Failure Measles, mumps, or rubella disease (or lack of immunity) in a previously vaccinated person 2%-5% of recipients do not respond to the first dose Caused by antibody, damaged vaccine, record errors Most persons with vaccine failure will respond to second dose

34. Measles (MMR) Vaccine Indications All infants >12 months of age Susceptible adolescents and adults without documented evidence of immunity

35. Measles Mumps Rubella Vaccine 12 months is the recommended and minimum age MMR given before 12 months should not be counted as a valid dose Revaccinate at >12 months of age

36. Second Dose of Measles Vaccine Intended to produce measles immunity in persons who failed to respond to the first dose (primary vaccine failure) May boost antibody titers in some persons

37. Second Dose Recommendation First dose of MMR at 12-15 months Second dose of MMR at 4-6 years Second dose may be given any time >4 weeks after the first dose

38. MMR Adverse Reactions Fever 5%-15% Rash 5% Joint symptoms 25% Thrombocytopenia <1/30,000 doses Parotitis rare Deafness rare Encephalopathy <1/1,000,000 doses

39. MMR Vaccine and Autism Measles vaccine connection first suggested by British gastroenterologist Diagnosis of autism often made in second year of life Multiple studies have shown no association

40. MMR Vaccine and Autism “The evidence favors a rejection of a causal relationship at the population level between MMR vaccine and autism spectrum disorders (ASD).” - Institute of Medicine, April 2001

41. MMR Vaccine Contraindications and Precautions Severe allergic reaction to vaccine component or following prior dose Pregnancy Immunosuppression Moderate or severe acute illness Recent blood product

42. The use of live-attenuated vaccine for post-exposure prophylaxis is contraindicated.

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