The majority of the patients are from the village of Starogladovskaya in the eastern part of the Northern Caucasus republic.
The first outbreak appeared several days ago, when several young girls and two schoolteachers started shivering, suffocating, and complaining of numb hands and feet. They were brought to the nearby town of Shelkovskaya for hospitalization, with the most seriously ill patients being transferred to Grozny, the republic's capital.
Sultan Alimkhadzhiyev, Chechnya's deputy health minister and the head doctor at Grozny's Republican Pediatric Hospital, told RFE/RL's North Caucasus Service that the first outbreak appeared in Starogladovskaya on 15 December.
"The following day, we learned that all people who were suffering from apparent poisoning were girls, aged between 12 and 16," Alimkhadzhiyev said. "That same day, after lunch, three children were brought [to our hospital]. One of them was in a critical condition, the other two in less serious state. They remained 24 hours in an intensive-care unit, after that we transferred them to a normal unit."
On 17 December, regional authorities said they had opened an investigation into the mysterious disease and for two days it looked as if the ailment had abated.
But Alimkhadzhiyev said new cases were reported on 19 December.
"On [19 December], another 12 children were brought to our hospital from Starogladovskaya. Most of them were suffocating, jumping on their beds, and shouting as if in a state of panic," Alimkhadzhiyev said. "It looked as if they were all suffering from psychosis. Our initial diagnosis was poisoning. That same evening, we admitted another two girls who were in an even more serious condition. Another two children were brought to us this morning. All in all, we now have 19 children [in the hospital]."
Alimkhadzhiyev said that the children suffer from bouts of sickness that last from 2 to 15 minutes and that the rest of the time they show no symptoms of illness.
Apparently, all the children affected by the mysterious disease are girls.
Health authorities have ruled out food poisoning.
Huseyn Nutayev, the head of the Shelkovskaya administrative district, has suggested that nerve gas could be responsible for the poisoning.
Nutayev on 17 December told Russia's Interfax news agency this was the third such bout of mysterious illnesses in recent years and that, in the previous two cases, doctors had not determined the cause of the ailment.
Alimkhadzhiyev, in turn, told RFE/RL's North Caucasus Service that heavy metals such as mercury could be responsible.
Meanwhile, reports from eastern Chechnya suggest the ailment has continued to spread.
Alimkhadzhiyev said two similar cases have been reported in the eastern village of Kharkovskaya. Russia's ITAR-TASS news agency on 19 December said four children from the village of Kobi, northeast of Grozny, were also being treated for similar symptoms.
The agency reported that the total number of patients was 39.
Alimkhadzhiyev said experts from Moscow were expected in Grozny soon to help their Chechen colleagues diagnose the illness.
RFE/RL's World: 2005 In Pictures
A slideshow of images related to the top news stories of 2005 from throughout RFE/RL's broadcast region with links to RFE/RL's reporting.