CURRENT EPIDEMIOLOGY OF POLIO IN PAKISTAN
As of 28th March 2014, 39 type-1 wild poliovirus (WPV) cases have been reported from seven districts/ towns/ tribal agencies/ FR areas (compared to six in 2013 from six districts/ towns/ tribal agencies/ FR areas). Moreover, WPV-1 has also been isolated from 11 environmental samples in 2014 (out of 52 samples for which results are available) from Gaddap, Baldia and Gulshan-e-Iqbal towns in Karachi Sindh, Peshawar in Khyber Pakhtunkhwa and Rawalpindi in Punjab. Six sabin-2 like poliovirus cases have also been reported from FATA, (four from North Waziristan agency and two from FR Bannu).
Following are the key epidemiological characteristics of polio cases reported in 2014 so far:
• 35 (89.7%) polio cases are younger than two years (median age: 16 months).
• Based on recall of parents, 34 (87.2%) cases did not receive any OPV dose (through routine vaccination and/or campaigns).
It is worth mentioning that, 82% (76/93) polio cases in 2013 and all except one in 2014 have been reported together from Khyber Pakhtunkhwa and FATA, indicating that these regions remain the key polio reservoirs in the country. Situ-ation in Karachi has also turned very concerning, consider-ing the fact that all the three high risk towns (Gadap, Gul-shan-e-Iqbal and Baldia) have the continuous presence of wild poliovirus during the last five months (positive environ-mental samples and polio cases). This situation in Karachi correlates with deteriorating quality of supplementary im-munization activities (SIAs) in 2013 and early 2014.
In Punjab, positive environmental samples were reported from Lahore and Multan towards the end of 2013. Rawal-pindi is the only district in Punjab which has detected wild poliovirus in 2014 so far. The available genetic analysis data confirms local circulation of wild poliovirus (type-1) since September 2013 which signifies substantial immunity gap. Rawalpindi is the only district other than Peshawar and Karachi which has consecutive positive environmental samples during the past four months. Considering these facts, there is likelihood of Rawalpindi turning into a polio reservoir, if urgent measures are not taken to immediately improve the quality of the upcoming SIAs. It is pertinent to mention that Rawalpindi has ongoing extensive population movement with parts of FATA and Khyber Pakhtunkhwa having intense wild poliovirus circulation.
Balochistan province that did not report any polio case dur-ing 2013, reported a positive environmental sample from Quetta (collected on 28th December). The genetic analysis of the isolated virus indicates missed viral circulation for more than a year; which in turn indicates missed popula-tions by the Supplementary Immunization Activities (SIAs) and AFP surveillance. The ongoing sub-optimal quality of SIAs in Quetta Block complements the findings of the ge-netic analysis. An impending polio outbreak cannot be ruled out in the region.
It is important to highlight that environmental samples from Faisalabad and Sukkur have been negative for over a year and in Hyderabad for the last six months.
In conclusion, poliovirus circulation in the country can be seen over a wider geographically area (compared to first half of 2013). The low transmission season however pro-vides a superb opportunity to stop the wild poliovirus circu-lation. With almost one month left in the season; the follow-ing is to re-emphasize as key to stopping wild poliovirus circulation:
Consistent access to all the children in reservoirs of Peshawar (and central Khyber Pakhtunkhwa) and Ka-rachi Gaining access to North and South Waziristan and consistently vaccinating all the children in Khyber agency (particularly Bara tehsil)
Highest quality SIAs in Punjab, interior Sindh and Balo-chistan to avert the risk of introduction and establish-ment of wild poliovirus,
High quality vaccination activities (routine and SIAs) for populations on the move from polio reservoirs.