Sick Leave
If an employee takes sick leave for another condition during his or her period of GRTW, it will not affect the compensation entitlement. Payment will continue to be made by both Comcare and the employer, as if the GRTW had not been affected.
The only difference is, the employee will be receiving sick leave payments instead of earnings from the employer.
This is because the employee already had certification for the compensable injury and was clearly still suffering from the condition, irrespective of the other illness.

Sick leave will continue to accrue for the employee when he or she is within the first 45 weeks of incapacity. This is in line with section 116 (a) of the Act, which states:
“... sick leave and recreation leave entitlements continue to accrue in relation to the employee during each of the first 45 weeks during which he or she is on compensation leave.”
After the first 45 weeks the employee's rate of sick leave accrual will be proportional to the amount of hours he or she is at work (if any).
Source URL: https://clik.dva.gov.au/military-compensation-reference-library/historical-information/comcare-operations-manual/volume-ten-incapacity-payments/part-four-graduated-return-work-and-reduced-work-capacity/difficult-cases-involving-grtw/sick-leave