The personal health information of thousands of Albertans was skimmed from the Alberta Health Services Edmonton network in May as a computer virus infected the network.

Alberta Health Services has sent letters to the 11,582 people whose information may have been captured by the virus between May 14 and May 29.

Notification has been sent by mail and should be received within the next seven business days.

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Bill Trasford, senior vice-president and chief information officer for Alberta Health Services speaks with CBC about a computer virus that attacked the AHS Edmonton network. (CBC)

"The actual virus got into our systems, and we detected it and had to wait some time ...  before we had a means from the anti-virus vendors to completely clean it out," Bill Trasford, senior vice-president and chief information officer for Alberta Health Services said Wednesday.

The computer virus that infected computers in the AHS-Edmonton network, believed to have been introduced by an external computer, was new and previously unknown to the AHS anti-virus software vendors, Trasford said. That's why the virus was not detected before it infected the network, he added.

AHS was not specifically targetted by the virus

"The way the virus worked, it would capture what was on a computer screen and then transmit it out to an external website," Trasford said. "So lab results, diagnostic imaging reports, things like that," he said.

The health information affected contains no financial information, he added.

Once the virus was detected, AHS worked quickly to remove the virus and take necessary steps to reinforce anti-virus protection, Trasford said.

After examining each of the 100 to 150 affected computers and their logs, AHS officials said they were able to identify the people whose information may have been captured by the virus.

"We can't guarantee that another virus won't get in some how, some way, so we will spend a lot of time ensuring that our ability to detect it and clean it out very very quickly is at the very very top end of the scale," he said.

AHS is currently completing a review of its Information Technology security measures.