Forewarning of Poliovirus Outbreaks in the Horn of Africa: An Assessment of Acute Flaccid Paralysis Surveillance and Routine Immunization Systems in Kenya

Indigenous wild poliovirus has been eliminated in 98% of endemic countries since 1988, with a decrease from 350 000 cases in 1988 to 223 confirmed cases in 2012 [1]. The success of polio eradication efforts has been dependent on increasing population immunity through routine immunization and supplementary immunization activities and by improving surveillance for acute flaccid paralysis (AFP). AFP surveillance systems are expected to annually identify ≥2 nonpolio AFP (NPAFP) cases per 100 000 population under 15 years of age to demonstrate that their systems are sensitive enough to detect paralytic polio cases [2]. All countries within the Horn of Africa region have successfully eliminated endemic poliovirus circulation, with Kenya successfully presenting in 2005 their complete country documentation outlining polio-free status. However, the region has remained at high risk for reintroduction and has had multiple outbreaks in recent years. An outbreak of 19 cases of wild poliovirus occurred in Turkana, Kenya, in 2009, and was followed by an outbreak of 22 cases in Uganda in 2010. In 2011, another wild poliovirus case was detected in western Kenya and was found to be genetically related to the 2010 outbreak in Uganda. These outbreaks indicated missed circulation within the region over a 3-year period. As of 31 December, 203 confirmed cases of WPV had been confirmed in the Horn of Africa in 2013. All of these outbreaks underscore the regional struggle to achieve the surveillance sensitivity and population immunity necessary to prevent transmission of imported poliovirus. In the midst of these outbreaks, the health system in Kenya has been decentralized, with both increased administrative autonomy at the district level and an increase in number of districts. Following a risk analysis performed in January 2012, which showed that 121 of 159 (77%) of districts in Kenya were at high or medium risk for a polio outbreak, the Kenya Ministry of Public Health and Sanitation (MoPHS) engaged the US Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), United Nations Children’s Fund (UNICEF), and other international partners to assist in a review of the national surveillance and routine immunization systems. The purpose of the review was to identify gaps in the programs, as well as to provide recommendations toward improving detection of imported poliovirus and preventing poliovirus circulation during this period of health system decentralization [3].