Tobin Chisnall has opened his eyes and tried to pull out his feeding tube, the first sign of improvement from the little boy in almost a week.
Read more: Mother's love comes to fore as illness strikes twice
The 3-year-old twin has been in a coma since contracting swine flu last Friday, which triggered a rare genetic disorder that causes his immune system to attack the brain.
Yesterday, the Herald told how Tobin had succumbed to the same disorder that left his sister Lucia, now 7, brain damaged and almost blind.
Parents Jared and Sarah Chisnall have watched helplessly as three viral infections - chickenpox, swine flu and tonsillitis - activated acute necrotising encephalopathy of childhood (ANEC) in Lucia three times in her short life, rendering her with the cognitive function of a 2-year-old.
The immune regulation dysfunction is rare, with only 250 known cases worldwide. There is no cure.
So when Tobin, the Franklin couple's only son, became comatose from a viral illness last week, they feared the worst.
But just hours after their story was published, prompting a surge in donations to their Givealittle fundraising page, Tobin began responding for the first time in six days.
"It's really amazing and quite unexpected," Mrs Chisnall said. "He's opened his eyes a couple of times and he's trying to pull his feeding tube out, and he's tried to sit up a couple of times." She said the family were trying not to get too excited.
"Even though there is some improvement, we know the journey that's in front of him and it's harrowing."
She said Tobin's response began when he made a noise while being given a shower yesterday morning.
"It's just phenomenal ... until that point he was just a floppy rag doll."
After the family's story went public yesterday the Givealittle fund more than doubled to $57,500 last night.