It probably was an asked for and given resignation rather than ‘fired’. Surgeon General is not a cabinet level position any more is it?
From Wikipedia
The Surgeon General of the United States is the operational head of the U.S. Public Health Service Commissioned Corps (PHSCC) and thus the leading spokesperson on matters of public health in the federal government of the United States. The Surgeon General's office and staff are known as the Office of the Surgeon General (OSG).While it doesn't directly say so, I'd guess the Surgeon General is not a Cabinet position - although he or she has to be confirmed by the Senate, so look for the RATs to drag this one out also.The U.S. Surgeon General is nominated by the President of the United States and confirmed by the Senate. The Surgeon General serves a four-year term of office and, depending on whether or not the current Assistant Secretary for Health is a PHSCC commissioned officer, is either the senior or next most senior uniformed officer of the PHSCC, holding the rank of a vice admiral.
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The Surgeon General reports to the Assistant Secretary for Health (ASH), who may be a four-star admiral in the United States Public Health Service, Commissioned Corps (PHSCC), and who serves as the principal adviser to the Secretary of Health and Human Services on public health and scientific issues. The Surgeon General is the overall head of the Commissioned Corps, a 6,500-member cadre of health professionals who are on call 24 hours a day, and can be dispatched by the Secretary of HHS or the Assistant Secretary for Health in the event of a public health emergency.