KEYWORDS:
Poliovirus Vaccine Circulation

BACKGROUND:
In 2000 a poliomyelitis outbreak due to vaccine-derived poliovirus was detected in Dominican Republic and Haiti. Subsequently, the Pan American Health Organization (PAHO) developed a protocol to identify other countries at potential risk for silent circulation of poliovirus. Ecuador was identified as a country at increased risk.

OBJECTIVE:
To develop an instrument to identify potential high-risk areas within a country and field test it in Ecuador.

METHOD:
Provinces were classified at increased risk using the following criteria: 1) level of coverage with OPV3, and 2) quality of surveillance for acute flaccid paralysis (AFP). National referral hospitals and at least 2 main health-care institutions were selected in each province identified at increased risk. We searched discharge logs for diagnoses compatible with AFP during the preceding 3-5 years, and cross-checked identified cases with those previously reported. Sewage samples from 1-2 major cities in each selected province were tested for poliovirus.

RESULT:
Six provinces were identified at highest risk: Esmeraldas, Cotopaxi, Bolivar, Napo, Loja and Manabi. Discharge diagnoses were reviewed for 326,752 patients. Fourteen patients with AFP compatible diagnoses were identified in the visited health-care units. Of them, 57% (8/14) had been reported and correctly investigated. Four out of 6 unreported cases were visited and none of them had sequelae compatible with polio, the other 2 were lost to follow-up. The cases that had not been reported were mostly in 1996 and 1998, and only one case in 2000 in Manabi province. Sabin viruses were identified in 6 out of 14 environmental samples; no genetically drifted vaccined derived polioviruses were isolated.

CONCLUSION:
No evidence of undetected poliovirus circulation was found using this methodology.

LEARNING OBJECTIVES:
This is a simple and easy to implement tool that may be applied in other countries.