The World Health Organization (WHO) Regional Office for Africa has been supporting Ministries of Health to establish, strengthen and expand surveillance for diseases targeted by new vaccines as part of implementation of the Global Framework for Immunization, Monitoring and Surveillance and regional Integrated Disease Surveillance and Response.1,2 As part of this initiative, the African Rotavirus Surveillance Network was established in 2006 to generate country- and region-specific data on the burden of rotavirus diarrhea, to characterize and document the circulating rotavirus strains. These data were anticipated to inform decisions on rotavirus vaccine introduction into national immunization programs. Where possible, rotavirus surveillance was integrated with the surveillance for other vaccine preventable diseases including pediatric bacterial meningitis surveillance network that is similarly coordinated by WHO Regional Office for Africa.3 Hospital sites were selected based on defined criteria including those that cumulatively care for at least 100 children <5 years of age hospitalized for acute gastroenteritis per year. Also, hospital sites should have laboratory capabilities required to perform rotavirus diagnosis. WHO supports and contracts designated Rotavirus Regional Reference Laboratories and local universities to conduct regular training of participants from the network countries on rotavirus diagnostic techniques and good laboratory procedures as well as support regional external quality assurance and quality control programs. These RRLs also conduct rotavirus strain characterization to determine circulating rotavirus strains in the African region.
Over the past 7 years, the African Rotavirus Surveillance Network coordinated by WHO Regional Office for Africa has expanded from 4 sentinel sites located in 4 countries in 2006 to 34 sentinel sites located in 20 countries in 2012 (Fig. 1). Each of the participating sentinel hospitals conducts active surveillance for rotavirus diarrhea using a common surveillance protocol including case definition, laboratory techniques and data capture, sharing and analysis.4,5 Briefly, children who present to a sentinel hospital and meet the case definition [≥3 episodes of diarrhea (stools of a less formed character than usual) within a 24 hour period, <7 days before hospital visit, which is not explained by an underlying medical condition] are enrolled and a stool specimen collected. Basic demographic and clinical information is collected for every enrolled child. Stool specimens are tested by enzyme immunoassay at the sentinel hospital laboratories. A proportion of positive specimens are selected at random to represent all the months of the year and sent to RRLs for genotyping using RT-PCR.
From 2006 to 2012, a total of 42,693 children <5 years of age hospitalized for acute diarrhea in sentinel hospitals participating in the African Rotavirus Surveillance Network and reporting to WHO have been enrolled in the surveillance program (Table 1). Stool specimens were collected and tested from 38,950 (91%) of these children. The number of children enrolled annually has increased as the network has expanded over the last 7 years. A total of 15,313 (40.7%) specimens tested positive for rotavirus during the entire period with the percent positive ranging from 35.6% in 2008 to 49.1% in 2006.
Great variability in circulating rotavirus strains has been observed in African countries from year to year. G1P was consistently the most prevalent rotavirus strain varying from 14% to 31% of all circulating strains, and mixed G and P strains were also commonly detected (12–14%) during 2009–2012 (Fig. 2). Strains, such as G2P, G3P and G4P, which are routinely detected in developed countries are less common in Africa. Conversely, there are a number of strains including G1P, G2P, G3P, G1P , G9P, G12P and G12P commonly detected in the African region, accounting for 27–40% of circulating strains annually that are less common in developed countries. Notably, genotype P was the most prevalent, followed by P and P. In this regard, it is reassuring that clinical trials of rotavirus vaccines in Africa found that the vaccine effectiveness was similar against vaccine and nonvaccine strains.6 However, it is important to continue monitoring the rotavirus strains circulating in various settings as great diversity of strains exists and not all aspects could be evaluated in the clinical trials.
The African Rotavirus Surveillance Network has played an important role in establishing the burden of rotavirus disease in Africa and the data have facilitated country decisions on rotavirus vaccine implementation. With the increased awareness of the local epidemiology of rotavirus diarrhea and the availability of rotavirus disease burden data contributed by the surveillance network, countries have begun to introduce rotavirus vaccines into their national immunization programs with financial support from GAVI. The rotavirus surveillance network is also adapting to meet local needs for monitoring the impact of the vaccine program.7,8 For example, Ghana and South Africa, the first countries in Africa to introduce rotavirus vaccines into their national immunization program are using rotavirus surveillance to monitor trends in rotavirus diarrhea pre- and postvaccine introduction as well as using their surveillance sites as a platform to evaluate rotavirus vaccine effectiveness.9 Similarly, Rwanda, which joined the network in 2010 and introduced rotavirus vaccine in May 2012, and Tanzania, which introduced vaccine in 2013, are also conducting a vaccine impact evaluation using established sentinel surveillance platforms.
As more countries in Africa introduce rotavirus vaccine, the network will continue to play an important role in monitoring the impact of vaccine and providing key data to policymakers, physicians, parents and pediatric associations to encourage and sustain the use of vaccine national immunization programs. This model using a surveillance program to generate data to facilitate, to sustain introduction of a new vaccine and to monitor the impact of newly introduced vaccine can be adapted as other new vaccines become available for use. Also, this network can serve as a platform at the country level to collect data on additional disease causing pathogens. For example, Ministry of Health, Zimbabwe has been using established sentinel surveillance for rotavirus to document Congenital Rubella Syndrome (CRS) disease burden since September 2011.
The authors acknowledge GAVI Alliance for financial support to WHO; support from national expanded program for immunization Managers; national Ministries of Health; WHO EPI/surveillance officers; Inter Country Support teams (IST) including the Data Managers and country sentinel site implementation teams coordinating rotavirus Surveillance at different levels and support from Centers for Disease Prevention and Control.
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3. Standard Operating Procedures (SOPs) for rotavirus surveillance in Africa. 2010
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