"President Biden’s top aides were told on Friday that experts studying the mysterious illnesses affecting scores of diplomats, spies and their family members were still struggling to find evidence..."

"... to back up the leading theory, that microwave attacks are being launched by Russian agents. The report came in an unusual, classified meeting called by the director of national intelligence, Avril D. Haines, according to several senior administration officials who spoke on the condition of anonymity. The purpose of the meeting was to assess the investigations and efforts to treat victims of the so-called Havana syndrome — the unexplained headaches, dizziness and memory loss reported by scores of State Department officials, C.I.A. officers and their families. While Mr. Biden has said almost nothing publicly about the episodes, the National Security Council has begun an urgent effort to address the issue, and two separate task forces are now in operation...."

From "Mystery Attacks on Diplomats Leave Scores of Victims but Still Little Evidence/While the leading theory in the 'Havana syndrome' cases is directed microwave attacks, a classified session for senior government officials said months of investigation were inconclusive" (NYT).