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CURRENT EPIDEMIOLOGY OF POLIO IN PAKISTAN
As of 14th February 2014, 93 type-1 wild poliovirus (WPV) cases have been reported during 2013 from 23 districts/towns/tribal agencies/ areas (compared to 58 in 2012 from 28 districts/towns/tribal agencies/FR areas). Moreover, WPV-1 has also been isolated from 65 environmental samples in 2013 (out of 321 samples for which results are available) from Peshawar, Rawalpindi, Multan, Faisalabad, Lahore, Quetta, Hyderabad, and Gaddap, Baldia and Gulshan-e-Iqbal towns in Karachi. Forty eight sabin-2 like poliovirus cases have also been reported, 41 from North Waziristan agency (FATA), four from Gaddap town Karachi (Sindh) and one each from Jaffarabad and Mastung (Baluchistan) and Mohmand agency (FATA).
A total of 14 wild polio cases have been confirmed with date of on-set of paralysis in 2014; twelve from North Waziristan agency in FATA and two from Khyber Pakhtunkhwa (one each from Bannu and Peshawar districts). The polio case reported from Bannu seems epidemiologically to be extension of the outbreak in North Waziristan (genetic analysis in not yet available). Three sabin-2 like poliomyelitis cases have also been reported from North Waziristan agency in 2014 reinforcing the significant immunity gap.
Following are the key epidemiological characteristics of polio cases reported in 2013 so far:
77 (82.8%) polio cases are younger than two years (median age: 13 months).
Based on recall of parents, 53 (57%) cases did not receive any OPV dose (through routine vaccination and/or cam-paigns); 13 (14%) cases received 1-3 OPV doses, 10 (10.7%) received 4-6 doses; while 17 (18.3%) polio cases received 7 or more OPV doses.
Two polio cases had date of onset of paralysis in January, three in February, one in March, two in April, nine in May, four each in June and July, eight in August, 19 in Septem-ber, 14 in October, 10 in November and 17 polio cases had date of onset of paralysis in December.
It is worth mentioning that, 81.7% (76/93) polio cases in 2013 and all in 2014 have been reported together from Khyber Pakh-tunkhwa and FATA (2 and 10 polio cases respectively), indicat-ing that these regions remain the key polio reservoirs in the country. Situation in Karachi has also turned very concerning, considering the fact that all the three high risk towns (Gadap, Gulshan-e-Iqbal and Baldia) have the continuous presence of wild poliovirus during the last four months, indicated by environ-mental surveillance results and reporting of polio cases. This situation in Karachi correlates with deteriorating quality of sup-plementary immunization activities (SIAs) in 2013.
Persistent isolation of wild poliovirus in environmental samples from Lahore and Multan and reporting of polio cases from cen-tral Punjab indicates high likelihood of viral establishment in the province. The persistent viral isolation in Rawalpindi district con-tinues indicating very high vulnerability due to ongoing popula-tion movement with endemic areas of Khyber Pakhtunkhwa and FATA.
Balochistan province that did not report any polio case during 2013, has recently reported a positive environmental sample from Quetta. The genetic analysis of this environmental sample (collected on 28th December), and poliovirus isolated from a polio case from adjoining southern Afghanistan (date of onset: 21st December) indicates missed viral circulation for more than 18 months. This in turn indicates missed populations by the Supplementary Immunization Activities (SIAs) and AFP surveil-lance.
It is important to highlight that environmental samples from Fai-salabad and Sukkur have been negative for over a year and in Hyderabad for the last five months .
In conclusion, poliovirus circulation in the country can now be seen over a wider geographically area. The low transmission season however provides a superb opportunity to stop the wild poliovirus circulation; with just about two months left in the sea-son. It is to re-emphasize that:
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Consistently accessing all the children in reservoirs of FATA (North Waziristan, Khyber Agency in particular), Peshawar (and central Khyber Pakhtunkhwa) and Karachi is the key to stopping viral circulation in Pakistan
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The quality of SIAs in Punjab, interior Sindh Balochistan has to be of the highest quality to avert the risk of introduction and establishment of wild poliovirus,
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Populations on the move from polio reservoirs have to be given due attention during vaccination activities (routine and SIAs)