In the event the employee is not eligible or does not elect to retire under the Employees' Retirement System of Georgia, if eligible to do so after contracting tuberculosis or infectious hepatitis, the state institution, agency, or department by which he is employed shall continue to make contributions to the Employees' Retirement System of Georgia, based on the employee's total or reduced compensation, for the duration of his illness, not to exceed a maximum of 350 weeks. The employee may elect to continue his contributions to the Employees' Retirement System of Georgia based on his total compensation or on the reduced compensation received from the institution, agency, or department. The retirement credits and benefits of an employee receiving compensation under Code Section 31-29-1 shall be based upon the compensation elected and contributed on by the employee.