Brief Answer:
several things

Detailed Answer:
hello and thank you for your question
While an infection is a common cause of an elevated White blood count (WBC) several other things can cause it.
A common cause is an auto immune reaction. These are things like rheumatoid arthritis and lupus where the body's immune system turns on itself.
Certain drugs or medications can cause a reaction in the body that elevated the WBC.
Diseases of the bone marrow like leukemia or lymphoma can be a cause.
Severe allergic reactions and any sort of trauma to the body like an accident or surgery can cause it.
Smoking can also cause an elevated WBC.
Please remember that sometimes it is elevated one day and not the next, it is only concerning if it is persistent or increasing.
Please let me know if you have further questions.
Dr. Robinson

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