Certification of polio free status of any country requires non-polio AFP (acute flaccid paralysis) rate of at least 1 per 100,000 children below 15 years and at least 80% adequate stool collection rate for three consecutive years(1). Advisory Committee on Polio Eradication (ACPE), WHO, in October 2005 recommended an operational target for non-Polio AFP rate of at least 2/100 000 for all endemic countries(2).

India has made great progress towards eradicating polio and has had excellent AFP surveillance. Since 2004 there was rapid increase in the non-polio AFP rate, which reached 8 in 2007 (Table I). The increase in non-polio AFP rate is mainly limited to the two polio hyperendemic states of Uttar Pradesh and Bihar(3).

* Data before the implementation of virologic classification scheme not included. As on  5th Jan 2008

Non-polio AFP rate is really the incidence of AFP caused by diseases other than poliomyelitis. Hence non-polio AFP rate cannot be increased to raise the sensitivity of surveillance beyond the maximum (expected) incidence of non-polio AFP cases. It is significant to note that ACPE did not increase the certification target. There has been no reported outbreak of paralytic neurological illness in children in those states.

Bihar has the highest non-polio AFP rate in India. In 2005 the rate was 14 with 81% adequate stool rate. In 2006 the rate was 19 with adequate stool rate of 82%. In 2007 the rate is more than 22 and 87% adequate stool rate. However in 2005 only 33% of polio cases could be confirmed though the overall adequate stool rate of AFP cases was 82%(4). A high proportion of compatibles have been found in subsequent years and also in Uttar Pradesh. Presence of compatible polio cases is an indication of weakness in the surveillance system(5). Though it is impossible to completely eliminate them, increase in sensitivity of surveillance as indicated by very high non-polio AFP rate should lead to a reduction in the number of compatible polio cases.

It appears that the inclusion of large number of ‘suspected’ AFP has masked genuine AFP cases reported late and maintained adequate stool rate above 80%. Unless there is some other reason to explain this anomalous situation, very high non-polio rate may have to be considered harmful to the quality of polio surveillance. and polio eradication. This discrepancy of having more than 80% adequate stool rate for AFP, with considerably less propor-tion of polio cases being confirmed despite very high non-Polio AFP rate has to be urgently addressed.

Paul T Francis,
Associate Professor,
Department of Community Medicine,
Amrita Institute of Medical Sciences,
Cochin 682 026,
India.
E-mail: [email protected]