05/10/2012 04:00 EDT | Updated 07/09/2012 05:12 EDT

Helene Campbell, Double Lung Transplant Patient, Back In Hospital

A Lung Story/Twitter

TORONTO - Helene Campbell, the 21-year-old Ottawa woman recovering from a double-lung transplant, is back in Toronto General Hospital after experiencing shortness of breath.

A blog posting late Wednesday by her mother, Manon, says Helene was readmitted to hospital on Sunday night.

She is undergoing various tests to help determine the reasons for her shortness of breath and to help the medical team decide on a course of treatment.

Manon Campbell writes that infection and rejection remain major risks as it is for all transplant patients, especially at this stage of recovery.

She adds that while waiting for more tests and results, Helene’s attitude remains ”strong and positive.”

Campbell became the unofficial face of organ donation in Canada after attracting celebrity endorsements for her cause.

She was diagnosed with advanced idiopathic pulmonary fibrosis last October and underwent surgery at Toronto General Hospital earlier this month.

Pop superstar Justin Bieber helped catapult Campbell into the spotlight by endorsing her campaign.

Campbell later appeared on Ellen DeGeneres' daytime talk show via Skype and has been invited to return in person once she recovers.

Campbell has been keeping her supporters posted on her progress through her blog _ _ and her Twitter account, which currently boasts more than 14,000 followers.