Two out of three polio virus strains eradicated worldwide, says WHO

Only one polio virus strain now persists in the world, but the battle against the disease is far from over.

A child receives an oral Polio vaccine | Representational Image | Flickr

Bengaluru: The World Health Organization (WHO) announced Thursday that two out of three strains of the polio virus have been eliminated worldwide. The Type 3 strain was eradicated in 2019 while Type 2 was eradicated in 2015. The announcement was made on the occasion of World Polio Day, which is observed on 24 October.

Polio is an extremely contagious, incurable disease that can lead to paralysis and even death. It killed 3,50,000 people annually, till the late 1980s and was a major public health challenge for decades. It was only with the global polio vaccination drive, adopted by WHO, UNICEF and Rotary foundation in 1988, that the number of polio cases came down by 99 per cent to only 33 cases in 2018.

A continuing struggle

However, the disease has not been eradicated completely. In recent years, polio has re-emerged multiple times even as attempts are being made to quell it.

A huge vaccination campaign is under way in Philippines after polio suddenly resurfaced, in the wake of growing anti-vaccine sentiment, nearly 20 years after the country was declared free of the disease. In Zambia as well, the first case since 1995 was announced Wednesday.

In both these instances the disease emerged from the vaccine itself and affected the unprotected populace. A weak but live polio virus persists in vaccines and can revert back to its diseased form A new genetically modified polio vaccine shows promising ways to tackle this resurgence.

Consequently, the now eliminated Type 2 strain can also make a reappearance as the live virus from the Type 2 vaccines and can infect babies born after the vaccine drive. While the only way to combat this is through the same vaccines, but vaccinations at this stage also increase the risk of the disease.

The polio war in Africa and Afghanistan-Pakistan

Most countries in the world have made major improvements in numbers related to polio except Pakistan, Afghanistan and northern Nigeria — primarily because of lack of access to vaccines due to geopolitical conflict. Despite this, Africa is expected to be polio-free by 2020 and Nigeria, which accounted for half of all the world’s polio cases ten years ago, last recorded a case three years ago.

The war-torn Pakistan-Afghanistan border, compounded by the Taliban’s ban on door-to-door vaccine administration, is the only region left with an unprotected population. There have been only 88 cases so far this year in the region, albeit an increase from last year’s 33.

The WHO statement also provided details regarding cost savings — “The polio eradication efforts have saved the world more than US$27 billion in health costs since 1988. A sustained polio-free world will generate further US$14billion in savings by 2050, compared to the cost countries would incur for controlling the virus indefinitely.”