This is a “rare” disease that is becoming less rare, with neither a known cause nor cure.
It’s a progressive nervous system disorder that starts as muscle weakness in an arm or leg and can eventually lead to respiratory failure.
The symptoms can mimic polio or stroke, including the drooping of facial muscles on one or both sides.
It strikes mostly among children, and the incidence remains at 1 known case for every million people in the US. However, the rate has been increasing since 2014. We also don’t know how many incorrectly diagnosed cases exist.
One current theory is that while the disease isn’t contagious, it can be spread by mosquitoes. As with other diseases, the mosquito bites someone with the disease, picks up the disease from contact with the blood, and then gives the disease to the next person it bites. Lovely critters.
There’s an odd pattern to the known cases. They seem to spike in the late summer and early fall of every other year — 2018 being one of the high years for the disease. This is shown in the CDC chart below.
Please consult the sources listed below.