Look at these two pictures of Viktor Yushchenko, the opposition leader in the Ukraine. It’s hard to believe this is the same man, and the pictures were taken only four months apart. The AP reports that there are all sort of theories about what has happened to Yushchenko.

As Ukraine’s popular pro-Western opposition leader claimed victory Tuesday in hotly contested presidential elections, the mystery surrounding an appearance-altering illness that twice prompted him to check into a Vienna hospital persisted.

Yushchenko accused the Ukrainian authorities of poisoning him. His detractors suggested he’d eaten some bad sushi.

Adding to the intrigue, the Austrian doctors who treated him have asked foreign experts to help determine if his symptoms may have been caused by toxins found in biological weapons.

Medical experts said they may never know for sure what befell Yushchenko.

But the illness, whatever it was, has dramatically changed his appearance since he first sought treatment at Vienna’s private Rudolfinerhaus clinic on September 10.

Known for his ruggedly handsome, almost movie star looks, Yushchenko’s complexion is now pockmarked. His face is haggard, swollen and partially paralyzed. One eye often tears up.

Doctors at Rudolfinerhaus declined to comment Tuesday. By the time Yushchenko checked out of the clinic last month after returning for follow-up treatment, physicians said they could neither prove nor rule out that he had been poisoned.

Dr. Nikolai Korpan, who oversaw Yushchenko’s treatment in Vienna, said the cause of his illness remained “totally open.”

Doctors were unable to confirm suspicions of poisoning because Yushchenko first checked into the clinic four days after the symptoms appeared — too late for tests to show if poisoning had occurred, Korpan said.

At Rudolfinerhaus, Yushchenko underwent a week of intensive treatment for several illnesses, including acute pancreatitis, a viral skin disease and nerve paralysis on the left side of his face, Korpan said.

Clinic director Michael Zimpfer said doctors were unable to explain some of Yushchenko’s symptoms, particularly his strong backaches.