Download Epidemiology of Measles

Epidemiology of Measles
Prof. Ashry Gad Mohamed
Prof. of Epidemiology
 Highly contagious viral illness
 First described in 7th century
 Near universal infection of childhood in
prevaccination era
 Common and often fatal in developing
areas
500,000
450,000
400,000
350,000
300,000
250,000
200,000
150,000
100,000
50,000
0
Leading killer of children
We know WHERE . . .
AFR
SEAR
EMR
WPR
EUR
AMR
94 % of all measles deaths in 2000
No second opportunity for measles immunization ( 45 )
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.

Global Progress
Measles Mortality Reduction by 50% by 2005
(compared to 1999 : 875,000 deaths)
Estimated Measles Mortality by Year
900000
800000
700000
600000
500000
400000
300000
200000
100000
0
1999
2000
2001
2002
2003
2004
2005
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]
Measles Mortality Reduction in EMRO Region,
1999-2004 EMRO
Estimated Deaths
120,000
100,000
80,000
60,000
40,000
20,000
0
1999
2000
2001
2002
Year
2003
2004
Tunisia
Morocco
Libya
Syria
Lebanon Iraq
Palestine
Jordan
Egypt
Afghanistan
Iran
Kuwait
Pakistan
UAE Bahrain
Saudi Arabia Qatar
Oman
Sudan
Yemen
Djibouti
Somalia
Percent reduction in estimated measles
deaths by WHO region between 1999 and
2002
0
% reduction
-5
AFR
SEAR
WPR
EMR
-10
-15
-20
-25
-30
-35
-40
Region
EUR
Global
12000
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
100
98
96
94
92
90
88
86
84
82
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
Year
Percent coverage
Cases
Measles Case Counts and
Coverage Saudi Arabia 1983-2004
 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
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
Measles Clinical Features
 Incubation period 10-12 days
Prodrome
 Stepwise increase in fever to
103°F or higher
 Cough, coryza, conjunctivitis , malaise,
sneezing, rhinitis, congestion
 Koplik spots
Koplik's spots, are
pathognomonic in
measles, appear on
the buccal and
lower labial
mucosa opposite
the lower molars
as White spots
inside the mouth
Measles Clinical Features
Rash
 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
Child has a
rash caused
by measles
Measles
rash
covering
child's
arms and
stomach
Measles Complications
Condition
Diarrhea
Otitis media
Pneumonia
Encephalitis
Hospitalization
Death
Percent reported
8
7
6
0.1
18
0.2
Based on 1985-1992 surveillance data
Measles Complications by Age Group
30
Pneumonia
Hospitalization
25
Percent
20
15
10
5
0
<5
5-19
Age group (yrs)
20+
Measles Clinical Case Definition
 Generalized rash lasting >3 days,
and
 Temperature 101°F (>38.3°C), and
 Cough or coryza or conjunctivitis
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
Measles Virus
 Paramyxovirus (RNA)
 One antigenic type
 Rapidly inactivated by heat and light
Reservoir
 Human
Incubation period.
Clinical case
 No animal reservoir
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
 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.
 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
 Temporal pattern Peak in late
winter–spring
 Communicability 4 days before
to 4 days after rash onset.
Strategy for sustainable
measles mortality reduction
1. Strong routine immunization > 90%
• Reaching Every District Strategy
2. Provide second opportunity for
measles immunization
• One time only “catch-up” campaign ( < 15 )
• “Follow-up” campaigns every 3-4 years ( < 5 )
• Routine scheduled second dose / opportunity
3. Surveillance
4. Improved case management
Measles Campaigns in EMRO through 2005
Palestine
Bahrain
Preschool and school age (13)
School age (5)
Preschool age (1)
Ongoing (2)
Not done (1)
Measles Vaccines
1963
1965
1967
1968
1971
1989
2005
Live attenuated and killed vaccines
Live further attenuated vaccine
Killed vaccine withdrawn
Live further attenuated vaccine
(Edmonston-Enders strain)
Licensure of combined measlesmumps-rubella vaccine
Two dose schedule
Licensure of MMRV
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
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
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
Measles (MMR) Vaccine Indications
 All infants >12 months of age
 Susceptible adolescents and adults
without documented evidence of immunity
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
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
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
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
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
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
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
 The use of live-attenuated vaccine for postexposure prophylaxis is contraindicated.