Doctors in Toronto have been working for weeks to try to pinpoint the cause of the second SARS outbreak. Now, after poring over medical records and retracing patient movements, a connection is emerging between the first and second outbreaks.

Health investigators had been calling the two SARS outbreaks phase one and phase two. Now they say, they are really just one protracted outbreak. At the daily briefing, health officials called it "good news."

"The outbreak is one continuous outbreak, with a quiet period in the middle when the cases were relatively asymptomatic, very difficult to spot," explained Ontario Commissioner Of Public Safety, Dr. James Young.

Phase two, they say, has roots in the original outbreak at Scarborough Grace when an 80 year old woman was discharged March 17. She had been next to another patient who later developed SARS. But she never went into quarantine. And -- most importantly -- she never had any symptoms doctors considered to be SARS.

The woman's daughter, with whom she lived, is a nurse at North York General who developed signs of the pneumonia 13 days later. Public health officials think she carried it to the floor where the 96-year-old man considered the first case of SARS outbreak two later died.

But the connection raises a troubling question. The nurse never had any contact with the 96-year-old and was wearing masks and gloves while at work, until she went home ill. So how could she have given him the virus?

"When you are putting together a puzzle with pieces and you don't even know what the picture looks like it is a challenge," said Dr. Barbara Yaffe of Toronto Public Health. "So the investigation is continuing."

"It's a complicated picture. It's a puzzle."

Public health wouldn't make the link because the 80-year-old mother of the nurse, because she never had symptoms of SARS.

"The individuals who were affected through a perfectly asymptomatic individual, and these cases were investigated by Toronto public health and experts deemed them not to be SARS cases," says infection disease specialist Dr. Barbara Mederski.

Doctors now suspect that the virus was then spread from patient to patient either through contaminated surfaces, or hand to hand contact.

Officials point out that the new theory linking the nurse to these new cases is still just a theory. There is still an investigation underway.

With reports from CTV's Avis Favaro and Canadian Press