Hi,
Welcome to HCM,
Dengue is viral infection and known to reduce platelet counts, as he is in the hospital this can be monitored frequently and as he is having black stool it points out that bleeding in upper GIT hence if appropriate transfusion of PRP/Platelet concentrates may be given in consultation of treating physician.
Thrombocytopenia and other complications like DHSS are monitored.
Other supportive measures including avoiding any drugs which can possibly reduce platelets.
You can also consult a Hematologist.
Take care
Good Luck.

Hello and welcome to HCM.

Thank you for your query.

There is no specific treatment for dengue fever. The main treatment for dengue is to replace the lost platelets through platelet transfusion (if very low), although reactions are common (which sometimes make it difficult) to transfuse platelets at a rate at which it is required. There should also be antibiotic coverage. Regular and strict monitoring of the platelet count is vital. Once the platelet count stops dropping, discontinue the transfusion and watch for a rise in platelet count without any external help.

Other symptomatic treatment includes pain management, antipyretics, plenty of oral fluids, diet including prunes, etc. and rest.

I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications. I would gladly help you.

Best wishes.