Polio eradication--the validity of surveillance indicators

Area of Science:

• Public Health
• Epidemiology
• Infectious Disease Surveillance

Background:

• Polio-free certification requires robust surveillance systems to detect non-polio acute flaccid paralysis (AFP).
• Mpumalanga, South Africa, implemented an enhanced surveillance system to improve infectious disease reporting.

Purpose of the Study:

• To evaluate the effectiveness of an enhanced surveillance system in detecting non-polio acute flaccid paralysis (AFP) in Mpumalanga, South Africa.
• To assess the system's performance against the World Health Organization's (WHO) target rate for polio-free certification.

Main Methods:

• Enhanced surveillance training for hospital staff on nine infectious disease syndromes, including AFP.
• Implementation of weekly zero reporting for all units.
• Review of paediatric admissions to identify missed AFP cases.

Main Results:

• The non-polio AFP reporting rate increased from 0.56 in 1997 to 0.91 per 100,000 children in 1998.
• Reporting rates met or approached the WHO target of 1 per 100,000 children between 1999 and 2001.
• Only five AFP cases were missed by the enhanced surveillance system during the study period.

Conclusions:

• The enhanced surveillance system in Mpumalanga significantly improved the detection of non-polio AFP cases.
• The system demonstrated potential for meeting WHO polio-free certification criteria, despite challenges with low reference rates and population variability.
• Continued attention to surveillance sensitivity is crucial for global polio eradication efforts.