Hi and welcome to Healthcare magic. Thank you for your query.
It sound slike infection which is most commonly viral and it can cause not just hight WBC
,but low too. Inmost cases it dosent indicate something serious,but there is a risk of some hematologic disease. He needs to repeat tests in few weeks after the signs of infection subside. Than his blood picture can be adequately evaluated.
Wish you good health. If you have any question I ll be glad to help.