There May Be A New Polio Epidemic On Its Way- If So, What We Can Do: Part III

This is Part III in a series on the enteroviruses that appear to cause a polio-like neurological disease, Acute Flaccid Myelitis. Hopefully we can use what we have learned from both the success and challenges of poliovirus vaccines to mount a formidable defense against emerging enteroviruses such as those causing Acute Flaccid Myelitis.

Poliomyelitis, more commonly known as polio, has nearly been eradicated worldwide. This is mostly thanks to effective vaccines and the expansive vaccination efforts reaching virtually all ends of the world. Afghanistan and Pakistan are now the only countries left in the world where polio is endemic. However, there have already been multiple cases of paralysis due to polio reported across the globe this year, from Malawi to Ukraine, and poliovirus was very recently detected in wastewater in London. These outbreaks are evidence that the two polio vaccines currently in use are not sufficient to reach complete eradication, and the development of an even safer and more effective vaccine is essential.

Despite the overarching success of vaccination against poliovirus, the push for complete eradication has faced considerable setbacks, with some recent discouraging ones. The entire continent of Africa was declared free of the wild poliovirus in 2020, but at least two new cases were reported in Malawi and Mozambique this year. They were discovered in young children who were both paralyzed as a result of the infection, meaning there are likely other unidentified cases as well. In 95% of cases, the poliovirus is only present in the bloodstream and the infection is asymptomatic. In 5% of cases, the virus spreads and replicates in other areas of the body outside of the bloodstream. The continued viral replication causes sustained secondary viremia and leads to the development of mild symptoms such as fever, headache, and sore throat.

Paralytic poliomyelitis, causing the paralysis polio is infamously known for, occurs in less than 1% of all poliovirus infections. This happens when the virus spreads into the central nervous system and replicates in motor neurons, leading to the selective destruction of said motor neurons in the spinal cord, brain stem, or motor cortex and resulting in temporary or permanent paralysis. We still do not really understand why the virus has very severe effects on some people but spares most others, and the frequency of asymptomatic cases means that there is a high likelihood of additional unidentified resurgent polio cases.

Originally published on Forbes on June 28, 2022. Read the full article on Forbes.

© William A. Haseltine, PhD. All Rights Reserved.