Poliomyelitis alert on Tunisian borders: response and challenges

INTRODUCTION: Poliomyelitis, which disappeared in Tunisia 30 years ago, should be the second disease to be eradicated after smallpox. However, a few endemic foci persist and its recent detection in some regions is causing great concern. On January 11, 2023, Tunisia received an alert with the notification of 2 polio cases in Algeria, the second of which was detected in November 2022 at about 400 KM from Tunisia. The objective of this study is to describe the results of the investigations following this alert as well as the prevention and response measures triggered. METHODS: We conducted an active search for acute flaccid paralysis (AFP) cases in all governorates and a retrospective search for possible unreported AFP cases hospitalized from November 1, 2022. Vaccination coverage was verified for catch-up if incomplete vaccination. Surveillance of poliovirus shedding in patients with primary immunodeficiencies (PIDs) was also conducted as well as other public health measures. RESULTS: As of April 20, 2023, 38 AFP cases have been reported through active search. Retrospective hospital-based surveillance has revealed 31 cases. In addition, 3142 children with deficient vaccination were identified, distributed differently by region. All of them were caught up with Inactivated polio vaccine (IPV). A total of 90 PIDs were followed up. The replacement of the Oral polio vaccine (OPV) dose at 6 months by IPV in the national immunization schedule as well as a request for verification of the possibility of using the new OPV2 in Tunisia and of the required requirements were made. CONCLUSIONS: The risk of poliomyelitis resurgence in our country is not negligible. Sustained vigilance is necessary, particularly through ensuring high vaccination coverage and effective surveillance to rapidly detect any imported case. This is essential in view of the global context and the existence of outbreaks especially in certain African countries with which several exchanges and migratory flows remain. KEY MESSAGES: • The Poliomyelitis alert on Tunisian borders in January 2023 is a real threat, that should also be taken into consideration by neighboring countries. • Sustained vigilance is necessary, particularly through effective surveillance and appropriate vaccination strategy.