Outbreak Response to Circulating Vaccine-Derived Poliovirus in Three Northern Regions of Ghana, 2019

Abstract

Background: Circulating Vaccine-Derived Poliovirus Type 2 (cVDPV2) was isolated in sewage and later in stool samples from children with acute flaccid paralysis (AFP) in northern Ghana. Method: A multidisciplinary and multisectoral team investigated this outbreak and reported on epidemiological and laboratory investigations. Sewage/wastewater samples were collected from the environment, while stool samples were collected from AFP/contact children under 5 years of age. The samples were processed for virus isolation, and positive isolates were sequenced. We also conducted a descriptive investigation involving a review of records, active case search, and Monovalent Oral Polio Vaccine 2 campaigns. Additionally, we interviewed caregivers about the vaccination status of their children, as well as their knowledge on polio prevention. Water quality, sanitation, hygiene practices, and health-seeking behaviours were also assessed. Results: A total of 18 cVDPV2 were confirmed in the three regions of Ghana during the outbreak in 2019-2020. All strains were genetically linked to a Nigerian cVDPV2 strain NIE-KWS-KSB-18-006HC29 that circulated in 2018. Evaluation of the surveillance system shows that officers have good knowledge of AFP and know how to collect samples, package them, and ship them to the laboratory. Few communities had access to potable water. Open defecation was common, and the water supply, sanitation, and hygiene practices of the communities were poor. Conclusion: The cVDPV2 outbreak represents the first time cVDPV2 has circulated in the country since Ghana embarked on the polio eradication program in 1996. However, with quality mOPV2 mop-up campaigns, a nationwide IPV catch-up campaign coupled with enhanced surveillance measures, transmission was interrupted.

Keywords: acute flaccid paralysis (AFP); circulating vaccine-derived poliovirus (cVDPV); environmental surveillance; northern Ghana; outbreak investigation.

Figure 1

Map of the Northern, Savannah, and North East regions (formerly Northern Region) of Ghana with district locations where cVDPV2 were isolated. The round spot indicates a single cVDPV2 from AFP, while the triangle represents the total cVDPV2 from ES.

Figure 2

Environmental surveillance site at Koblimahgu in the Tamale Metro District.

Figure 3

Phylogenetic analysis of cVDPV2 that circulated in the Northern Region in the 2019 Ghana outbreak. Black squares indicate cVDPV2 from AFP and contacts. Black circles represent cVDPV2 from environmental samples. “F” at the end of the environmental isolate Epid number represents the flask number that was positive.