Rubella Epidemiology in Africa James L Goodson 10 th Annual Measles Initiative Meeting Washington...

Rubella Epidemiology in Africa

James L Goodson10th 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.

• Background

• Rubella epidemiology in Africa in the prevaccine era, 2002-2009– Methods– Results– Summary

Presentation Outline

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*Modelling results, unpublished, Adams E, Vynnycky E**Lawn, J.E., et al., Unseen blindness, unheard deafness, and unrecorded death and disability: congenital rubella in Kumasi, Ghana.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

Source: WHO and UNICEF, 2011

3 have introduced rubella-containing vaccine

Cape Verde

Seychelles

Mauritius

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

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.

< 10%

10-24%

≥ 25%

Unknown

During 1963-2009, sero-susceptibility results for women of reproductive age from 12 countries

Laboratory-confirmed Rubella Cases, WHO African Region,

2002-2009 (N=25,631)


Laboratory-confirmed Rubella Cases by Sex and Setting, WHO African Region, 2002-2009

(N=25,631)

Cases

n n % n % n %

25,631 12,271 50 10,527 63 6,255 37

Setting*

Female Rural Urban

*Information on location (rural vs urban) was available for 16,782 (65%) cases


Laboratory-confirmed Rubella Cases by Age Group, WHO African Region, 2002-2009

(N=25,631)

Cases

n n % n % n % n % n % n %25,097 775 3 7,063 28 11,799 47 4,131 16 1,329 5 1,305 5

5 - 9 y 10 - 14 y ≥ 15 y

Age* GroupWomen of

Reproductive Age (15 - 49 y)< 1 y 1 - 4 y

*Information on age was available for 25,097 (99%) cases


Frequency of Laboratory-confirmed 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)


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


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 – SeasonalityIn 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

• 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

Congenital Rubella Syndrome

• 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

Rubella Epidemiology

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

Rubella Epidemiology in Africa James L Goodson 10 th Annual Measles Initiative Meeting Washington...

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