Hello Welcome to HCM Yes,dengue is the most common cause for low platelet count.Virus causing dengue fever attacks the body s immune system by causing destruction of the platelets. In your present situation, as counts are less, along with the blood transfusion,patient needs platelets transfusion immediately to prevent bleeding diathesis like intracranial haemorrhage. Along with this supportive treatment with steroids,antipyretics and fluids is very much essential.It may also require ICU admission and more vigilant monitoring. Thank you.