ISLAMABAD: Nine more environmental samples, collected from all the four provinces, have been found to be positive for Type-1 wild poliovirus (WPV1), taking the tally of positive tests for the current year to 83.

Besides, Badin has been included in the list of 30 districts whose sewage water carries the virus of the crippling disease.

The Regional Reference Labora­tory for Polio Eradication at the Na­­t­ional Institute of Health, Islam­a­bad, has confirmed the detection of WPV1 in the sample from Badin dis­­­trict, while eight samples have been found positive from six previously infected districts — Chaman, Karachi Malir, Karachi South, Kara­chi East, Peshawar and Lahore.

“The virus isolated from the samples is genetically linked to the YB3A poliovirus genetic cluster, which disappeared from Pakistan in 2021, remained in circulation in Afghanistan and was reintroduced through cross-border transmission in January 2023. This virus has been found in all positive samples,” a health ministry official told Dawn on Friday, adding that two polio cases have been reported this year.

43m children vaccinated in each of two drives conducted this year

He expressed concern over rapid increase in environmental samples just before the start of high transmission season of poliovirus.

“The increase in temperature will increase the chances of new cases or infections in children having weak immunity level or those who missed vaccinations or their parents deliberately dodged the polio teams,” he said, requesting anonymity since he is not authorised to speak to media.

When asked about the high transmission season, the official said, “Poliovirus remains less active in the low transmission season from September to April because of lower temperatures. However, it becomes more active from May to August, due to which more children can be infected.”

He explained that a sample is considered positive if poliovirus is detected in sewage water. A sewage water sample from an area is the basic parameter to determine if polio vaccination campaigns are being carried out successfully or not.

“A polio case can be reported in any city due to frequent movement of people from one city to another, but the presence of virus in sewage water means that a vaccination campaign in the area has not met its target. The presence of virus in the sewage water also shows that the immunity level of local children has fallen and they are at the risk of contracting the disease,” he said.

The Pakistan Polio Programme has already conducted two nationwide polio eradication campaigns this year, vaccinating more than 43 million children under five in each of the two drives. In addition, an outbreak response campaign is going on in 26 districts, including Chaman and Sukkur, to boost children’s im­­m­unity. Yet another campaign is plan­ned for April and coming months.

Published in Dawn, March 30th, 2024