KEYWORDS:
Polio, eradication, surveillance, immunization, India

BACKGROUND:
Global eradication efforts have reduced endemic polio transmission to 20 countries, with India reporting the largest number of cases.

OBJECTIVE(S):
Measure progress and identify strategies for successful eradication of polio.

METHOD(S):
Polio cases are identified by a national system for surveillance of acute flaccid paralysis (AFP) with weekly reporting from 8,566 reporting units, and managed by 232 Surveillance Medical Officers, supported by eight WHO-certified laboratories. The global standard for sensitivity of AFP surveillance has been sustained since May 1998. Case-based data are analysed weekly for all 35 States and 580 Districts. Twice each year since 1995, national polio immunization days (NIDs) reached 120-150 million children with oral polio vaccine (OPV). Additional supplemental immunization activities (SIAs) have included two extra NIDs in 1999, six sub-national immunization days, and 26 large-scale (>1,000,000 children) house-to-house “mop-up” campaigns.


RESULT(S):
The number of polio cases dropped 99% from an estimated 35,680 widespread cases in 1994 to 193 cases to date (11 Dec ’01) in 2001, with 173 (90%) of 2001 cases being from two adjacent States where routine immunization coverage is <50%. The number of affected Districts dropped 86% from 401 in 1998 to 55 in 2001, with 85 (44%) of all 2001 cases being from four adjacent Districts. Type 2 poliovirus was last reported in October 1999. Except for 1999, type 1 poliovirus has predominated over type 3, and only four genetic lineages of type 1 remain in circulation. 67% of 2001 cases were minority children, 87% were 0-24 months of age, and 62% had received >3 doses of OPV.

CONCLUSIONS(S):
Poliovirus transmission in India has been greatly reduced. Eradication depends upon continuing high-quality NIDs and other SIAs targeting underserved children in high-risk areas, while improving routine immunization.


LEARNING OBJECTIVES:
Understand methods, progress and prospects for polio eradication in the largest remaining endemic country.