New Wild Poliovirus Cases Confirmed in Pakistan

The Islamic Republic of Pakistan is one of two countries left in the world where poliovirus continues to threaten the health and well-being of its 250 million residents.

According to the weekly report published by the Global Polio Eradication Initiative (GPEI), Pakistan confirmed four new wild poliovirus type 1 (WPV1) cases. WPV1 is the only circulating wild poliovirus serotype.

The latest instances of paralysis were in Balochistan, Khyber Pakhtunkhwa, and Sindh provinces.

Furthermore, 50 WPV1-positive environmental samples were recently confirmed from Balochistan, Islamabad, Khyber Pakhtunkhwa, Punjab and Sindh.

As of October 14, 2024, Pakistan has reported 28 cases of WPV1 this year.

Since 1994, the Pakistan Polio Eradication Program has been fighting to end poliovirus infections. Through its efforts, case numbers in Pakistan have declined by up to 99% from the 20,000 cases reported in the early 1990s.

Unfortunately, the WHO reconfirmed in August 2024 that the spread of the poliovirus remained a Public Health Emergency of International Concern.

The U.S. CDC reported in September 2024 that routine immunization coverage with oral polio vaccines (OPV) and inactivated polio vaccine (IPV) in Pakistan has improved in recent years, as IPV protects against paralysis.

However, because it is an inactivated vaccine that does not replicate in the intestinal tract, as does OPV, it does not prevent the spread of poliovirus.

This could partly explain the relatively low number of WPV1 cases reported in the context of widespread WPV1 circulation as evidenced by environmental surveillance.

However, one-half of all WPV1 patients had never received OPV through routine immunization, indicating population immunity gaps. Whenever feasible, vaccination activities need to be synchronized with those of neighboring Afghanistan, says the CDC.

In Africa and Asia, the nOPV2 vaccine has been offered in 2024.

In the United States, the IPV has been offered since 2000, and booster doses are recommended for certain international travelers in 2024.