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Earlier this year, I reported on an outbreak of a mysterious viral disease that exhibited polio-like symptoms. At the time, around 23 children and young adults were afflicted with the disease. Some of them tested positive for enterovirus-68, a member of a genus of viruses that include over 66 different species that can infect humans. None of them tested positive for the polio virus.
Polio is a crippling and potentially deadly infectious disease caused by the poliovirus, a human enterovirus, that spreads from person to person invading the brain and spinal cord and causing paralysis. Because polio has no cure, the polio vaccine is the best way to protect yourself and the only way to stop the disease from spreading.
The United States last experienced a polio epidemic in the 1950s, prior to the introduction of the polio vaccine 60 years ago. Today, polio has been eradicated from most of the planet, as the number of worldwide polio cases has fallen from an estimated 350,000 in 1988 to fewer than 223 in 2012—a decline of more than 99% in reported cases.
This week, researchers at the Centers for Disease Control and Prevention reported on results of testing of 23 individuals who presented with acute flaccid paralysis (AFP) with anterior myelitis (AE)–that is, a muscle weakness or paralysis along with an infection of the grey matter of the spinal cord. In general, these are symptoms of paralytic polio, though many other viruses can present with the same symptoms.
What did the current study find?
- Most of the patients were tested, by the California Department of Public Health, for evidence of recent infection with numerous infectious agents, including EVs (including poliovirus), arboviruses, herpes viruses (HSV-1, HSV-2, VZV, and EBV), parechoviruses, adenoviruses, rabies, influenza A and B, human metapneumovirus, respiratory syncytial virus, parainfluenza 1–4, Mycoplasma pneumoniae, rickettsial pathogens, and free-living amoebas.
- The poliovirus was not discovered in any samples.
- Two patients were confirmed to have enterovirus-68, supporting the preliminary results from earlier this year (that I discussed).
- Full medical information was available for 14 of the 23 patients. Of those 14, 12 were vaccinated against polio while 2 had personal belief exemptions.
- As I mentioned in my earlier article about this outbreak, the positive tests for enterovirus-68 in two of the patients was confirmed in the current study.
One interesting point that was mentioned was that some of the treating physicians took some time before they hypothesized that it was polio because…polio was eradicated.
After all of this, what can we conclude?
First of all, AFP is extraordinarily rare, so rare that we might only see 1.4 cases per 100,000 population. In California, based on that incidence rate, we might expect to see much more than 23 individuals, so what we might be observing may not be an outbreak, but just a set of random unrelated events, which, based on this study, have no common infectious disease.
Second, polio was ruled out. This was not polio. These diseases are unrelated to polio. And the polio vaccine had nothing to do with it (given that 2 out of 23 people were unvaccinated, making the risk of AFP technically higher for unvaccinated individuals than vaccinated ones based on this limited sample).
There are a lot of rare diseases, some serious. For the parents of the children who presented with AFP, it’s definitely sad and frustrating, because it appears that the paralysis may not be treatable. If the virus becomes more widespread, and more outbreaks occur (or are recognized because of this study), a new vaccine may have to be developed. This is why we have epidemiologists, infectious disease specialists, virologists and microbiologists at leading institutions like these medical schools, WHO and the CDC who monitor diseases. They are the frontline heroes of detecting, treating and eventually preventing novel diseases. We should be thankful to them.
- Ayscue P, Van Haren K, Sheriff H, Waubant E, Waldron P, Yagi S, Yen C, Clayton A, Padilla T, Pan C, Reichel J, Harriman K, Watt J, Sejvar J, Nix WA, Felkin D, Glaser C. Acute Flaccid Paralysis with Anterior Myelitis — California, June 2012–June 2014. Morbidity and Mortality Weekly Report. 2014 September;63:1-4. PubMed PMID:
- Oberste MS, Maher K, Schnurr D, Flemister MR, Lovchik JC, Peters H, Sessions W, Kirk C, Chatterjee N, Fuller S, Hanauer JM, Pallansch MA. Enterovirus 68 is associated with respiratory illness and shares biological features with both the enteroviruses and the rhinoviruses. J Gen Virol. 2004 Sep;85(Pt 9):2577-84. PubMed PMID: 15302951.