Outbreak Of Mysterious Paralyzing Condition Squashed By COVID–19 Pandemic

The grim pall of the COVID-19 pandemic ensures that 2020 will go down as an infamous year in the history of human disease.

But this dark chapter held some surprises we can be thankful for, too. In a new study, researchers found that a predicted 2020 outbreak of a mysterious paralyzing illness failed to materialize on schedule – and in a weird way, we actually have the coronavirus to thank for it.

The condition in question is called acute flaccid myelitis (AFM). This polio-like neurological disease mainly affects children, causing muscle weakness and, in some cases, permanent paralysis and even death.

For decades, cases of AFM were very rare, but in recent years, larger outbreaks across the US and elsewhere have occurred, seemingly reoccurring every two years.

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A body of previous research has linked AFM to a rare virus called enterovirus D68 (EV-D68), and while it's not yet known how the virus manifests the symptoms of the AFM disease, coinciding outbreaks of the pair have led researchers to think they are almost certainly related.

In the new research, a team led by first author and infectious disease modeler Sang Woo Park from Princeton University tracked patterns of cases of EV-D68 between 2014 and 2019, with the virus staging significant resurgences in even-numbered years – 2014, 2016, and 2018 – which are thought to be attributable to climate-based factors.

The data suggested 2020 was due for another hit.

"We predicted that a major EV-D68 outbreak, and hence an AFM outbreak, would have still been possible in 2020 under normal epidemiological conditions," the researchers explain in their study.

Of course, as the world was at pains to witness, the epidemiological conditions of 2020 were anything but ordinary, and the expected combo hit of EV-D68 and AFM never came.

In the US – a country with significantly more cases of COVID-19 than any other – the combined effects of physical distancing, quarantine and isolation policies, and economic and civic shutdowns all appeared to not just diminish the spread of SARS-CoV-2 but EV-D68 as well.

"Our preliminary analysis indicates that the COVID-19 pandemic response is likely to have affected the dynamics of a 2020 EV-D68 outbreak," the authors write.

According to the researchers, there were 153 cases of AFM in 2016 and 238 cases in 2018, but just 31 cases in 2020.

In light of everything the US has been through in recent times, these are some numbers to feel good about.

Still, there's no time for complacency – especially as EV-D68's unplanned gap year may have left a larger than usual void in viral immunity at the population level.

"On the basis of the low number of [predicted] EV-D68 cases in 2019, we would expect the number of susceptible individuals to have increased, enhancing the probability for a large outbreak to occur," the team says.

"If social distancing prevents the outbreak from occurring, then the susceptible pool may increase even further."

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