Thrombocytopenia is known to occur in dengue fever, which promptly recovers usually by 9-10 days of illness. However, persistent thrombocytopenia may have following possible mechanisms:
(a) Dengue virus induces bone marrow suppression
(b) Dengue virus can bind to human platelets in presence of virus specific antibody and cause immune mediated clearance of platelets.
(c) Spontaneous aggregation of platelets to blood vessel wall cells pre-infected by virus inducing aggregation, lysis and platelet destruction.
(d) Anti-platelet antibodies generated after dengue virus infection causes destruction of platelets.
Bone marrow examination demonstrating the presence of adequate megakaryocytes, with coexistent thrombocytopenia at a time when the virus was normally expected to have been cleared will ensure that there is no marrow disease causing thrombocytopenia. Thus bone marrow examination would not be out of place. Treatment with methyl prednisolone may cause recovery of the platelet counts. I would suggest meeting a good clinical haematologist for further investigations and treatment if required.