Rubella Epidemiology in
Africa
James L Goodson
10th Annual Measles Initiative Meeting
Washington D.C.
September 13-14, 2011
On Behalf of Co-investigators
Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D,
Cochi S, Susan Reef; Rubella Epidemiology in Africa in the Prevaccine
Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Presentation Outline
• Background
• Rubella epidemiology in Africa in the
prevaccine era, 2002-2009
– Methods
– Results
– Summary
Background
• 42,440 (Range 9,130 – 97,228)* cases of
congenital rubella syndrome (CRS)
estimated to occur each year in the WHO
African region
• Routine CRS surveillance non-existent in
the region
– Pilot site in Ghana in 1996-97 identified 18
infants with CRS during a 5-month period**
• Rubella epidemiology in the region
previously not well described
*Modelling results, unpublished, Adams E, Vynnycky E
**Lawn, J.E., et al., Unseen blindness, unheard deafness, and unrecorded death and disability: congenital rubella in Kumasi,
Ghana. American Journal of Public Health, 2000. 90(10): p. 1555-61
46 Countries in the WHO African Region, 2011
Source: WHO and UNICEF, 2011
46 Countries in the WHO African Region, 2011
3 have introduced
rubella-containing
vaccine
Cape Verde
Seychelles
Mauritius
Source: WHO and UNICEF, 2011
Methods
• Literature review
• Surveillance data analysis
Methods: Literature Review
• PubMed search engine was used to find
previously published rubella seroprevalence
studies in Africa
• A study was included if the article reported
seroprevalence results and contained a
description of study design, study
population, and age group(s) tested
Methods: Surveillance Data Analysis
• Regional measles case-based surveillance
data from 40 countries during 2002–2009
• Data collected following WHO guidelines
– Suspected measles case definition
• illness with a generalized maculopapular rash and
fever, and ≥1 of the following: cough, coryza (runny
nose), or conjunctivitis
Methods: Surveillance Data Analysis
• Blood specimens tested using ELISA
– For measles-specific IgM antibody
– If results were negative or indeterminate, then
tested for rubella-specific IgM
• For the analysis of age, sex, and setting
(urban/rural), we included countries with ≥30
laboratory-confirmed rubella cases during
2002–2009
• Divided the countries into 4 sub-regions
based on geography
Results
Results: Literature Review
• During 1963–2009, there were 22 reports of
rubella seroprevalence from 14 (30%) of 46
countries
• Rubella susceptibility ranged from 1% – 29%
and varied by age group
– In the 3 largest studies (N>1000), estimates of rubella
susceptibility among women of reproductive age range
from 6%–16%
Rubella Susceptibility among Women of
Reproductive Age, WHO African Region
During 1963-2009, serosusceptibility results for
women of reproductive
age from 12 countries
< 10%
10-24%
≥ 25%
Unknown
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Laboratory-confirmed Rubella Cases, WHO
African Region,
2002-2009 (N=25,631)
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Laboratory-confirmed Rubella Cases by Sex and
Setting, WHO African Region, 2002-2009 (N=25,631)
Setting*
Cases
Female
Rural
n
n
%
n
25,631
12,271
50
10,527
Urban
%
n
%
63 6,255
37
*Information on location (rural vs urban) was available for
16,782 (65%) cases
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Laboratory-confirmed Rubella Cases by Age Group,
WHO African Region, 2002-2009 (N=25,631)
Age* Group
Cases
<1y
n
n %
25,097 775 3
1-4y
5-9y
10 - 14 y
n %
7,063 28
n %
11,799 47
n %
4,131 16
≥ 15 y
n %
1,329 5
*Information on age was available for 25,097 (99%) cases
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Women of
Reproductive
Age (15 - 49 y)
n %
1,305 5
Frequency of Laboratoryconfirmed Rubella Cases by Age
in Years, 2002-2009, WHO
African Region (N=25,097)
Overall, mean age of cases was
7.3 years (IQR=4.2–9.0 y)
Information on age and setting
available for 16,627 (65%) cases
In urban settings, mean age was
6.8 years (IQR=3.9–8.5 y)
In rural settings, mean age was
7.5 years (IQR=4.2–9.8 y)
(P=.004)
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Laboratory-confirmed Rubella
Cases by Month of Rash Onset, 4
Geographic Subregions,
2002–2009, WHO African Region
South
•distinct annual seasonality
•consistently few cases Jan–June
•gradual increases, peaks Sept–Oct
•East
•reporting varied
•biphasic, peaks Mar–Apr, Sept–Oct
•troughs Dec–Jan and May–June
•Central
•data were sparse
•peaks generally Feb–Mar
•troughs Sept–Nov
•West
•distinct annual seasonality
•sharp increase Jan, peaks Mar–Apr
•declines May, troughs Oct–Dec
Reference: Goodson JL, Masresha B, Dosseh A, Byabamazima C, Nshimirimana D, Cochi S, Susan Reef; Rubella
Epidemiology in Africa in the Prevaccine Era, 2002–2009. J Infect Dis. 2011 July 1, 2011;204(suppl 1):S215-S25.
Limitations
• Seroprevalence studies, small convenience
samples, results not representative
• The surveillance data represents a small
fraction of all rubella cases
– Cases were detected through surveillance
designed to detect measles
– 20%–50% rubella infections do not have rash,
therefore, clinical presentation may not meet
suspected measles case definition
– Potential reporting bias toward groups wherein
suspected measles cases occurred, such as in
younger age groups
Summary:
Rubella Epidemiology in Africa
• Estimates of rubella susceptibility among adults range
from 1%–29%
– In the 3 largest studies, estimates of rubella susceptibility among women of
reproductive age range from 6%–16%
• Rubella virus is circulating widely in Africa
– Primarily infecting young children
– By 15 years of age most have immunity from natural infection
– 5% of reported rubella cases occur in women of reproductive age
• Suggests rubella infection during pregnancy, potential CRS, remains largely undetected
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Back-up Slides
Discussion – Age Distribution
• During prevaccine era in Europe and the
Americas
– Age distribution was similar to that in Africa, primarily
a childhood disease, mainly among 5- to 9-year-olds
– In the United States
• 80% of reported cases occurred by 14 years of age
• 92% by 20 years of age
• However, seroprevalence studies estimated susceptibility
among those17–22 years of age was 15%–20%
Discussion – Urban vs. Rural
• During prevaccine era in Europe, Americas, and Asia
– Immunity to rubella in rural settings was lower than in urban
settings; and is consistent with our finding of an older mean
age of reported cases in rural settings than in urban settings in
Africa.
• The significantly younger mean age of reported cases
in urban settings compared with that of rural settings in
Africa may be due to rubella infection occurring at
younger age in areas with high population density and
contact rates.
Discussion – Seasonality
In the United States, prevaccine era, annual seasonality
of rubella was observed, with an increase in cases
occurring in the early winter, peaking in March and
decreasing to a low point in late summer and autumn; in
general, annual seasonal peaks in rubella cases occur
during springtime in temperate climates.
We found similar seasonality in the South subregion of
Africa, which includes countries located in the southern
temperate zone.
Discussion – Seasonality
In the United States, prevaccine era, annual seasonality
of rubella was observed, with an increase in cases
occurring in the early winter, peaking in March and
decreasing to a low point in late summer and autumn; in
general, annual seasonal peaks in rubella cases occur
during springtime in temperate climates.
We found similar seasonality in the South subregion of
Africa, which includes countries located in the southern
temperate zone.
Rubella Disease
• 20-50% of infections are asymptomatic
• Prodrome
– Rare in children
– Adolescents/adults: low grade fever, malaise,
lymphadenopathy, upper respiratory symptoms
lasts1- 5 days
• Rash
– Maculopapular
– Begins on face and head
– Usually persists 3 days
• Other symptoms
– Lymphadenopathy: postauricular, posterior
cervical, and suboccipital
– Conjunctivitis
Congenital Rubella Syndrome
• Infection in pregnancy, most dangerous <12 weeks
gestation
• May lead to fetal death or premature delivery
• Hearing impairment, cataracts, heart defects,
microcephaly, developmental delay, bone alterations,
liver and spleen damage
• Organ specificity generally related to stage of
gestational infection
Rubella Epidemiology
• Reproductive number (R0) lower than for measles
• High coverage with single dose of rubella vaccine
can provide herd immunity
• Usual inter-epidemic interval: 6-9 years
• Rubella /CRS elimination goal achievable by
targeting children through existing measles control
strategy but women of child bearing age must also
be covered
Results: Literature Review
• 3 studies of women of reproductive age with
N>1000
– 94.1% (95% CI, 93.0%–95.2%)
• women 14–18 years of age (N=1,696) in Ethiopia
• Gabreselassi & Abebe1985
– 90.1% (95% CI, 89.2–91.1)
• women 15–45 years of age (N=3,471) in Senegal
• Dromigny et al. 2003
– 84.0% (95% CI, 83.0%–85.0%)
• women 15–34 years of age (N=4,866) in Cote d’Ivoire
• Vrinat et. Al 1978