Status of poliomyelitis after pulse polio immunization.

I read with interest the recent publication(1) on this subject. Since Kalawati Saran Childrens Hospital is a sentinel centre for surveillance of Poliomyelitis, covering the states of Delhi, UP, MP and HP, the figures are reliable and informative. It is heartening to note that the occurrence of poliomyelitis in these states has reduced to 369 cases in 1996 from 1062 cases in 1994. Does this figure apply to stool culture positive cases of polio or to all AFP cases? It is important to note that there are a significant number of cases in the months of December 1994, 1995 and 1996, disproving our belief that December month, like January, is a low transmission period for wild polio virus. Since the timing of Pulse Polio Immunization Programme (PPIP) in December and January is dependent on the assumption that these two months of a year constitute low transmission period, do we need to change the timing of PPIP to say, MarchApril each year, which have reported the lowest number of cases in 1994, 1995 and 1996? And also, these two months form the rain free period and off season for farmers.