"She told me her son was getting married and she didn't want to cause trouble for the new couple," Zhang says. 

Bone transplant surgery leaves scars on two SARS survivors' legs.

"Their fears actually became a motivation for my work. I felt I should do something to help ... Making their stories known is the first step to eliminating misunderstandings and discrimination."

To present a fuller view of the post-SARS years, in 2007, Zhang sneaked into Xiaotangshan Hospital.

The temporary shelters, which were built within a week to house more than 680 SARS patients and were shut down after operating for 51 days, were completely deserted and out of bounds to the public.

Standing in front of the hospital, she felt fear and fatigue.

Entering the shacks, Zhang fell silent as she looked at the scattered documents, dust-covered glass bottles, empty file cabinets and rusting bed railings.

"It was suffocating and I felt as though that eerie silence was trying to tell me something. I was scared and couldn't help wondering if the virus was really gone."

Zhang's first trip to Xiaotangshan lasted less than an hour, as she was haunted by both the fear of catching SARS and running into the security guard and his dog.

However, as she fled the site and noticed the new apartments cropping up nearby, Zhang knew she had to return.

"These stories had to be told before they got buried by the bulldozers," she says.

She went back to Xiaotangshan several times and remembers washing her hands repeatedly after looking at the documents.

"It was ridiculous, but I feared the virus was still attached to them," Zhang says. "I had the same reaction every time I had to touch the stuff there. "

Her photographs appeared at the 3rd Guangzhou International Photo Biennial, in 2009.

It was a small exhibition called the SARS Sequela, with fewer than 30 pictures on show.

"In a dramatically-changed society, the pain (of SARS) can be quickly forgotten. Zhang's works keep the memories alive," says Li Mei, chief curator of the photo biennial.

Meanwhile, for Zhang, the job is not yet done.