Rubella is a disease of public health significance, largely owing to the teratogenic effects of the virus, and is characterized by multiple birth defects known as congenital rubella syndrome (CRS). Common birth defects are ocular (cataracts, retinitis, microphthalmia, and glaucoma), hearing impairment, heart defects (pulmonary stenosis, persistent ductus arteriosus), microcephaly, developmental delay, mental retardation, bone alterations, and damage to the liver and spleen . Other adverse outcomes of rubella infection in early pregnancy or just before conception include foetal resorption, spontaneous abortion and intrauterine foetal death. It is estimated that the majority (90%) of infants with CRS are born to women who were infected by rubella virus in the first 10 weeks of pregnancy .
It is estimated that more than 100,000 infants worldwide are born with CRS each year. Africa, the Western Pacific and Southeast Asia are regions known to have the highest burden of CRS [3,4]. The incidence of CRS is estimated to be between 0.1 and 0.2 cases per 1000 live births. This incidence rises to 1–4 cases per 1000 live births during rubella outbreaks. In the prevaccine era, rubella was responsible for over 11,000 foetal deaths and there were 20,000 infants born with CRS in the United States during an epidemic between 1964 and 1965. Routine rubella vaccination in the US began in 1969, and by 2004, the country was declared free of endemic rubella .
Nearly 136,000 cases of rubella were reported in the Americas in 1998, predominantly in southern regions. In 2003, Pan American Health Organization member countries established a goal to eliminate rubella and CRS from the Western Hemisphere by 2010, under a background of outbreaks during the 1990s . This goal was achieved when the last cases of endemic rubella were reported in 2009, and the eight cases reported in Canada and the US were found to be imported .
The World Health Organization (WHO) European Region set a measles and rubella elimination goal by 2010 (resolution EUR/RC55/R7 of 2005) under a background of rising rubella incidence, especially in central and Eastern Europe and the post-Soviet states . Through increased immunization efforts, the incidence of rubella was reduced from 233 cases in 2005 to 13 in 2009 per 100,000 population .
Meanwhile, rubella has been circulating widely in Africa. Estimates of rubella prevalence are obtained primarily from combined measles/rubella case-based surveillance conducted according to the guidelines of the WHO Regional Office for Africa (WHO/AFRO) . Goodson et al. analysed rubella seroprevalence data from Africa from 17 published reports and estimated that 1–29% of adults and 6–16% of women of child-bearing age (15 to 49 years) in the region are susceptible to rubella . The majority (95%) of rubella cases reported in this survey had occurred in children up to 14 years of age.
In Zimbabwe, surveillance for rubella was introduced in 1999 through the existing measles surveillance system. The measles case definition (children and adults presenting to health facilities with rash and fever plus at least one of the following: coryza, conjunctivitis or cough, or any person in whom a clinician suspects measles) was also adopted for rubella surveillance. All samples negative for measles IgM antibodies by serological testing are subsequently tested for rubella. This approach may underestimate the burden of rubella because the surveillance is not primarily designed to identify rubella but rather to identify measles. Some rubella infections are missed because they do not meet the “suspected measles” case definition. The WHO/AFRO measles surveillance guidelines require that the testing algorithm exclude measles IgM-positive cases from rubella screening.
In 1969, a serosurvey of nine common respiratory viruses, including rubella virus, was completed over a period of 3 months, among 112 children and adults of the Korekore tribe in northern Zimbabwe who visited a local mission hospital. Blood samples were tested for rubella antibodies using the haemagglutination inhibition assay. The study found 88% rubella seropositivity among the study population . This high rate of seropositivity suggested a recent rubella outbreak around the time of the serosurvey. A measles and rubella epidemic occurred in Zimbabwe in 1977–1978, which resulted in sudden detection of an unexpected number of cases of rubella embryopathy in infants born at a major African referral hospital . It was suggested that this epidemic was fuelled by population movement because of the escalation of war during the same period. In the literature, it has been suggested that rubella epidemics usually occur at intervals of approximately 7–10 years. This is also supported by data from The Gambia where epidemics were serologically diagnosed during 1963–1964 and 1973–1974 .
Owing to the existing burden of rubella in some regions of the world, the WHO recommends introduction of rubella-containing vaccines as a strategy to control the disease. Rubella vaccination programmes are economically justifiable and have demonstrated cost-effectiveness. Published economic analyses for the period between 1980 and 2010 indicate that the annual cost (inflation-adjusted 2012 US$) for the care of a patient with CRS in middle-income countries ranges from US$4,200 in Brazil to US$58,000 in Panama, whereas the lifetime cost for the care of a patient with CRS in high-income countries (inflation-adjusted 2012 US$) is estimated to be US$139,900 in Oman and over US$200,000 in the United States .
The WHO recommends that prior to introduction of rubella vaccine to national immunization programmes, rubella surveillance should be implemented through the existing measles surveillance system to estimate the disease burden . In line with the WHO strategy for rubella vaccination in Africa, our analysis of data from Zimbabwe’s combined measles/rubella case-based surveillance system aims to describe the trends and population demographics of children and adolescents with rubella in the country, who were identified through its national surveillance system during a 5-year period between 2007 and 2011.