Catherine Hughes' son Riley died from pertussis (also known as whooping cough) in March, 2015, at just 32 days old. She's since been campaigning for education about the dangers of whooping cough, and promoting the need for vaccination - which is offered as standard to pregnant women in the UK - through her Facebook page, Light for Riley.
Her latest update is an emotional message to all of the staff at Perth's Princess Margaret Hospital, who supported her throughout his illness and passing.
'Thank you to the nurses who helped entertain our daughter with toys and games when Riley was dying in hospital,' she wrote.
'Thank you to the clever doctor who correctly diagnosed Riley before receiving the swab results back, just by the sound of his cough.'
'Thank you to the PICU doctors and nurses who kept us calm in an environment where you feel sad, desperate and scared.'
'Thank you to the doctor who told me there was a chance Riley could die. I didn't like you at the time, purely because your words felt like huge punch in the gut, but it was important we were prepared.'
'Thank you to the kind nurses who tried to make sure we ate, drank, and rested when all we could think about was whether our son would make it or not.'
'Thank you to the doctor who put her own family's life on hold while she worked tirelessly, staying back late and coming in early.'
'Thank you to the doctor who sat with us in the family room with the unenviable task of telling us that it was unlikely Riley would survive.'
'Thank you to the nurses and doctors who gave us time and space to say goodbye to our son as he passed away in our arms.'
'Thank you to the young nurse who came down to PICU after she heard that he didn't make it, and cried with us.'
'Thank you to the nurse who carefully took his little hand-prints and foot-prints for us.'
'Thank you to the nurse who held our son's body in her arms as we left the hospital, sobbing.'
'Thank you to the nurse who stopped us in the hallway as we left, shocked that he didn't make it, and hugged us tightly.'
'Thank you to the nurse who came to Riley's funeral and said such kind words to us.'
'And thank you to all the incredible doctors and nurses out there who talk to patients about the importance of vaccines, and what can happen when babies who are too young to be vaccinated contract a vaccine-preventable disease.'
She concluded by adding: 'Doctors and nurses don't just save lives - they do so much more. I know sometimes they receive a lot of abuse, but they really deserve our gratitude and thanks for all that they do.'
The letter has since been shared more than 1,000 times, with commenters applauding Catherine's kind sentiments.
'Beautiful - as an ICU nurse i loved reading this, it so wonderfully described the ICU care we work tirelessly to provide for patients & families,' one said. 'We grieve with families every day - it shakes us & tests us on every level but no matter what happens we keep going to be there in those darkest hours to do everything we can & we exhaust ourselves as well as every option to pull our patient's through.'
Another agreed: 'I am honoured being a nurse as it means I get to meet such gracious and loving families such as yours. To me nursing is not just a job, it's part of who I am. I am so sorry for the loss of Riley.
'What a legacy you are making in his memory, so thank you for speaking out on the importance of vaccination.'