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Updated: Mar 17, 2026
Particle Agglutination Method for Poliovirus Identification
Published on: April 20, 2011
Contribution of Contact Sampling in Increasing Sensitivity of Poliovirus Detection During A Polio Outbreak-Somalia,
Edna Moturi1, Abdirahman Mahmud2, Raoul Kamadjeu3
1Epidemic Intelligence Service; Global Immunization Division.
Abstract:
Background. In May 2013, a wild poliovirus type 1 (WPV1) outbreak reported in Somalia provided an opportunity to examine the contribution of testing contacts to WPV detection. Methods. We reviewed acute flaccid paralysis (AFP) case-patients and linked contacts reported in the Somalia Surveillance Database from May 9 to December 31, 2013. We restricted our analysis to AFP case-patients that had ≥3 contacts and calculated the contribution of each contact to case detection. Results. Among 546 AFP cases identified, 328 AFP cases had ≥3 contacts. Among the 328 AFP cases with ≥3 contacts, 93 WPV1 cases were detected: 58 cases (62%; 95% confidence interval [CI], 52%-72%) were detected through testing stool specimens from AFP case-patients; and 35 cases (38%; 95% CI, 28%-48%) were detected through testing stool specimens from contacts, including 19 cases (20%; 95% CI, 14%-30%) from the first contact, 11 cases (12%; 95% CI, 7%-20%) from the second contact, and 5 cases (5%; 95% CI, 2%-12%) from the third contact. Among the 103 AFP cases with ≥4 contacts, 3 (6%; 95% CI, 2%-16%) of 52 WPV1 cases were detected by testing the fourth contact. No additional WPV1 cases were detected by testing >4 contacts. Conclusions. Stool specimens from 3 to 4 contacts of persons with AFP during polio outbreaks are needed to maximize detection of WPV cases.
Insights
Testing stool specimens from 3 to 4 contacts of individuals with acute flaccid paralysis (AFP) is crucial for maximizing wild poliovirus type 1 (WPV1) detection during outbreaks.
Area of Science:
- Epidemiology
- Infectious Disease Surveillance
Background:
- A wild poliovirus type 1 (WPV1) outbreak in Somalia in 2013 presented an opportunity to evaluate contact tracing effectiveness.
- Understanding WPV detection strategies is vital for global polio eradication efforts.
Purpose of the Study:
- To assess the contribution of testing contacts to the detection of wild poliovirus type 1 (WPV1) during an outbreak.
- To determine the optimal number of contacts to test for maximizing WPV detection.
Main Methods:
- Retrospective review of acute flaccid paralysis (AFP) case-patients and their linked contacts in Somalia from May to December 2013.
- Analysis focused on AFP cases with at least three contacts to calculate the detection yield per contact.
- Statistical analysis of WPV1 detection rates based on the number of contacts tested.
Main Results:
- Of 328 AFP cases with ≥3 contacts, 93 WPV1 cases were identified.
- Directly reported AFP cases accounted for 62% of WPV1 detections.
- Testing contacts identified 38% of WPV1 cases, with 20% from the first contact, 12% from the second, and 5% from the third.
- Testing the fourth contact identified an additional 6% of WPV1 cases; no further cases were found beyond four contacts.
Conclusions:
- Testing stool specimens from 3 to 4 contacts of individuals with AFP is necessary to maximize WPV detection during outbreaks.
- Contact testing significantly contributes to identifying WPV cases, complementing direct case reporting.
