By Anupam Srivastava
PATNA: After they simmer in the 40-plus heat for two months, when the north Indian plains do get the monsoon showers, it is a time for celebration. The rainy season, however, brings with it an increased risk of poliovirus transmission. Bihar, one of the two states endemic to the poliovirus, is in the grip of flooding as this piece goes to print. As many as 2,286,638 children – around one-tenth of the children who are vaccinated normally – were missed in the August round with 19 of the total 38 districts flooded. The flooding has been protracted, making the situation worse.
UNICEF Bihar Polio Unit Chief Dr. Anisur Rahman Siddique says that the districts that missed the last round fully or partially – East Champaran, Khagaria, Sitamarhi and Muzaffarpur – have ongoing transmission even in the low season which makes the children even more susceptible now that they have missed the opportunity of getting an additional polio dose. Uttar Pradesh experienced floods in a few districts at a smaller scale, particularly in five blocks of Baharaich district and parts of Varanasi, Azamgarh and Gorakhpur.
In Bihar, the round could not be held in certain limited areas within the blocks that did have immunization activity. There was also a reduction in transit coverage as movement of people was affected in the state. Epidemiologically, there is considerable risk of poliovirus transmission both due to a likely increase in the virus activity due to flooding as well as the reduced immunity of children due to incomplete immunization.
Bihar has reported 22 polio cases (all type 1) from 10 districts of the state (data as on September 5). Fifty percent of these cases were detected during the first two months of the year. Of the 11 cases detected since March this year, 10 cases are from a cluster of 4 districts in North Central Bihar (Madhepura, Saharsa, Darbhanga and Samastipur). Seventy percent cases detected in Bihar in 2007 are from the high-risk blocks that were identified earlier this year. These blocks have had polio cases more frequently and more consistently in the past and many of these are flood-prone. Genetic information available on 18 of the 22 cases of 2007 indicates that 2 of the 4 families circulating in 2006 have managed to survive into 2007.
Bihar this year has conducted eight polio rounds, all with the monovalent vaccine mOPV1 (the state has reported all type 1 cases this year) in the high-risk districts between January and August this year. While polio circulation in Bihar is geographically restricted so far, there is a potential risk of spread of the virus to other districts following the recent floods, as happened in 2004. However, the increased number of polio rounds in the state this year is expected to limit the spread of the virus as children this year are better-protected.
UNICEF’s social mobilisers have been helping the state office in mapping flooded areas for polio vaccination as well as for other interventions. As Bihar prepares for the polio round starting on September 9, the social mobilisers are working with the anganwadi workers of the ICDS department to identify and vaccinate newborns who are among the most susceptible groups.
India currently has 185 cases out of which 136 belong to the P3 strain virus – Uttar Pradesh has 133 of these. Bihar does not have a single P3 case at the moment and the P1 monovalent vaccine continues to be used in the state.
There has been an increase in the number of P3 cases in Uttar Pradesh over last year due to focussed vaccination against the P1virus. The P1 cases in India are reduced to 49 (last year there were 648 P1 cases in India) and epidemiologists feel a combination of P1 and P3 rounds can consolidate the gains for the programme.