World Health Organization Declares Second Strain of Polio Eradicated Worldwide

On October 24, 2019, the World Health Organization announced that wild poliovirus type 3 has been eradicated worldwide other than sample specimens held in laboratory containment.

In an historic announcement on World Polio Day, an independent commission of experts concluded that wild poliovirus type 3 (WPV3) has been eradicated worldwide. Following the eradication of smallpox and wild poliovirus type 2, this news represents a historic achievement for humanity.

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There are three individual and immunologically-distinct wild poliovirus strains: wild poliovirus type 1 (WPV1), wild poliovirus type 2 (WPV2) and wild poliovirus type 3 (WPV3). Symptomatically, all three strains are identical, in that they cause irreversible paralysis or even death. But there are genetic and virologic differences which make these three strains three separate viruses that must each be eradicated individually.

WPV3 is the second strain of the poliovirus to be wiped out, following the certification of the eradication of WPV2 in 2015. The last case of WPV3 was detected in northern Nigeria in 2012. Since then, the strength and reach of the eradication programme’s global surveillance system has been critical to verify that this strain is truly gone. Investments in skilled workers, innovative tools and a global network of laboratories have helped determine that no WPV3 exists anywhere in the world, apart from specimens locked in secure containment.

Will Polio Ever Be Eradicated?

The World Health Organization maintains that it will eradicate polio worldwide, but the disease is beginning to re-emerge in African countries that had previously been polio-free. Will anti-polio campaigners ever manage to eradicate polio?

The current outbreak in Africa is directly traceable to a decision by religious extremists in northern Nigeria to suspended polio vaccinations in 2003.

Shortly after that decision, polio cases in Nigeria began to spike. That was soon followed by cases popping up in nearby countries including Burkina Faso, Central African Republic, Chad, Ivory Coast, and Sudan. All five of those countries had been free of polio until 2003. Along with Nigeria, polio still persisted prior to 2003 in Egypt and Niger.

Polio has since spread to an additional seven African countries that had been free of polio, and the disease could spread further.

Admittedly the number of cases is still very small — Nigeria reported the most cases in Africa in 2004 at 763, but the outbreak of cases in previously polio-free countries is jacking up the costs of immunization. According to Dr. David Heymann, who heads up WHO’s polio eradication program, the resurgence of cases in polio-free countries will add at least $150 million to immunization efforts on the continent.


Health Officials Say They’ll End Polio In Africa, Despite Its Spread. Lawrence Altman, The New York Times, January 16, 2005.

More than 170 Million Indian Children Receive Polio Vaccination

In what was billed as a major effort to eradicate polio from India, more than 170 million children under five were vaccinated against polio over a three day period earlier this month. Simultaneously, another 80 million children in 24 African nations were also vaccinated.

The goal is to eradicate polio from India by the end of 2005.

So far this year, India has reported 85 cases of polio, the lowest number ever since polio statistics have been recorded. In 1994, when efforts to eradicate polio from India began in earnest, there were 4,791 cases reported.

Deepak Kapoor, chairman of Rotary International in India which has played an important role in polio eradication in India and other parts of the world, told New Kerala,

If polio can be completely wiped off by next year, it would be a great victory, not just for India, but for the international community as a whole. It would induce a renewed confidence in our efforts against other diseases such as malaria and AIDS.

Unfortunately, eradicating polio in Africa might prove a bigger challenge. Planned vaccinations in Ivory Coast, for example, had to be canceled due to the unstable political and military situation in that country.


India starts ‘final’ anti-polio push. Ania Lichtarowicz, The BBC, November 21, 2004.

India inches closer to eradicating polio. New Kerala, November 21, 2004.

UN giving kids in India polio shots. United Press International, November 21, 2004.

No Link Seen Between SV40 in Polio Vaccine and Non-Hodgkin Lymphoma

In 1960, researchers discovered Simian virus 40 (SV40). Shortly afterward it was discovered that SV40 was also present in the injectable polio vaccine (it was not present in the oral version of the vaccine). Kidney cells from rhesus monkeys were used to prepare the vaccine, and it turned out that those cells were infected with SV40. In the early 1960s, researchers ensured that the polio vaccine was produced using cells that were not infected with SV40.

People were potentially exposed to SV40 for more than a decade, however, and over the years there have been any number of hypotheses that one illness or another has been caused by SV40 exposure from the polio vaccine. The latest claim is that SV40 increased the risk of non-Hodgkin lymphoma, a blood cancer. This claim was given some impetus by the discovery of SV40 in NHL tumors.

A population-based study of almost 1,400 individuals, however, suggests that there is no increased risk of non-Hodgkin lymphoma associated with exposure to SV40. Researchers at the National Cancer Institute tested blood samples from 724 patients with non-Hodgkins lymphoma and from 622 matched control patients without non-Hodgkins lymphoma.

The samples were tested at two independent laboratories. The first laboratory reported SV40 in 7.2 percent of the NHL patients and 10.5 percent of the control group. The second laboratory reported SV40 in 9.8 percent of NHL patients and in 9.6 percent of the control group. The results indicate there is likely no increased risk of developing NHL among individuals exposed to SV40.

Researchers also looked at incidence levels of specific types of non-Hodgkin lymphoma and also found no increased risk associated with SV40 exposure as well.


Monkey virus exposure did not raise lymphoma risk. Reuters Health, September 14, 2004.