Not many details, but events like this have historically been framed as examples of "sociogenic illness", even though the details are murky and it makes no sense anyway. They call it "Dinga dinga". Dancing seems like a stretch here, this looks more like rhythmic spasms or something like it and it only looks like dancing because dancing is also rhythmic. For sure it would fall under the concept of functional movement disorder to people with a "this is a functional disorder" hammer. Would sure be great if someone could figure this out and debunk a bit of the old nonsense. Video: And a report: https://timesofindia.indiatimes.com...y-in-this-infection/articleshow/116493254.cms. Although there are more symptoms than the 'spasms': Uncontrollable body shaking: The most striking feature of the illness is violent, involuntary movements that resemble dancing. Fever and extreme weakness: Patients often report high fever and overwhelming fatigue. Paralysis-like immobility: Some experience a sensation of paralysis, with even basic movements like walking becoming impossible.
In the Times of India article: Sounds like a serious brain dysfunction due to acute infection, the pathogen is unknown. It appears to be treatable with antibiotics with most people recovering in a week according to the article. I think the dancing plagues of the medieval era were down to ergot toxin (from fungi on rye stored in humid conditions if my memory serves me right). It causes writhing movements (chorea) and severe whole body tremors and psychosis. They advise people to seek medical attention and not to take home remedies. So the medical authorities are taking it very seriously. The small phone clip showing youth in Uganda is interesting, could be many things. Would be good to see medical reports on the phenomena.
While it's most likely choreiform movements as HibiscusWahine says, another possibility in those affected could be that the lower limb "dancing" is a way of ambulating by recruiting brain pathways alternative to the impaired normal walking circuits - similar to the flu vaccine-injured young woman (YouTube) who until she recovered could not walk normally but could run or even walk normally but only backwards. Spoiler: Sidenote If that were the case those of us with modest dancing skills and poor innate rhythm might be less able to compensate! In which case we'd stay fixed to the floor, swaying (sorry).
There was a related phenomenon in Medieval Europe, the origin of the dance tarantella. According tradition it was related to a spider bite hence the name of the dance, though I have also read the suggestion that it was more likely related to ergot poisoning via bread made with mould infected grain. Whatever the cause part of the outcome was frenzied dancing. For some at least this could lead to death, perhaps undermining any psychogenic explanation. [added - in twelfth and thirteenth century Italy it was believed that the frenzied dancing was the only way to get the poison out of your system.]