Dengue fever is a severe illness. So you most likely are suffering from Telogen Effluvium. Here the illness affects the hair growth and throws all the hair in the 'growth' phase into the Telogen or 'falling ' phase. It is a natural phenomenon. But this I am saying based on the nature of your complaint. A physical examination is needed to confirm what I said or otherwise.
Visit an allopathic dermatologist near you. Before you choose your dermatologist read this: http://www.skinmatra.com/single-post/2016/07/03/Skin-Troubles-Here-is-WHAT-NOT-TO-DO
Do not self medicate or use medicines based on hearsay.