Total WBC count of 2600 / cu.mm is something really to be worried. It commonly suggest septicemia
/ infection. However, the report should be correlated with child's clinical condition. It would be more helpful if you mentioned the complete investigation reports. Other causes like leukemia, bone marrow depression
, corticosteroid therapy, genetic disorders are possible. Thorough examination and investigations are necessary to diagnose the cause.
Please, get your child examined by pediatrician
IMMEDIATELY. He may require inject able antibiotics / other medicines.