A Fredericton teenager hospitalized with a potentially fatal strain of E. coli is slowly getting better and was allowed outside for the first time in two weeks over the weekend.

"She felt the sun on her face and started crying," said Victoria Boer, referring to her daughter Micaella Boer.

"And then she asked for a triple-triple Tim Hortons. It was small pleasures. So she got her little coffee and was just sitting there so happy."

Micaella, 18, has been hospitalized since July 3 and is being treated with blood plasma transfusions.

But doctors and nurses at the Saint John Regional Hospital said she could go outside "as long as she didn't go out for very long," said Boer.

"She gets very, very tired. And they were concerned about her falling, or whatever. So they agreed that if they put her in the wheelchair, she could sit outside," Boer said.

Boer smiles as she enjoys a Tim Hortons triple-triple coffee. (Facebook)

Micaella and one of her young male friends are two of the four confirmed cases of E. coli O157:H7 in Fredericton.

That's the same strain of E. coli that killed seven people during the tainted water scandal in Walkerton, Ont., in 2000.

Public health officials have not released any results from their investigation into the source of the outbreak of the infectious bacteria that can multiply quickly.

Dr. Denis Allard, the province's acting chief medical officer of health, has said lab results may be available this week, but also noted that in many E. coli outbreaks, the source is never identified.

Micaella developed severe symptoms shortly after Canada Day and is being treated with blood plasma transfusions up to twice a day. She may need at least 100 treatments, her mother has said.

Her friend is also undergoing blood plasma transfusions, according to Boer.

E. coli O157: H7 secretes a powerful toxin that can destroy red blood cells leading to severe illness, high blood pressure and kidney damage.

The main symptom for this strain of E. coli is bloody diarrhea, but it can also cause vomiting and stomach cramps. There is no fever.

Those most at risk of developing serious complications include pregnant women, young children, seniors and people with a weakened immune system, such as those on chemotherapy.

Doctors believe Micaella and her friend may have a slightly different strain, her mother has said.

The Fredericton cases follow an outbreak in Miramichi in April. At least 13 people were infected with the potentially deadly strain and another 11 people may have also been infected by the same strain, officials had said.

Romaine lettuce was recently determined to be the likely source of that outbreak.