All the victims are residents of several villages in the eastern Shelkovskaya district. Two-thirds of them are children, mostly girls. Local authorities have closed down all kindergartens and schools in the area until at least 26 December.
Officials say experts have not yet established the cause of the ailment, whose symptoms reportedly include sudden bouts of tremors, nausea, and shortness of breath.
Chechnya's top prosecutor, Valeri Kuznetzov, said on 22 December that experts have ruled out toxic or chemical poisoning as possible causes of the disease. He said radioactivity levels in the Shelkovskaya district were below permitted levels.
He said psychological disorders linked to long-time emotional stress were believed a likely cause of the illness.
The first case of the mysterious ailment was registered in Chechnya on 16 December.