In hantaviruses it is the internal bleeding you die from as over the progression of the disease cappliary beds ossmotic pressure that keeps the blood in the blood vessels change causing uncontrolled leakages into the interstial spaces. Hence people with hanta will have petechia in the eyes as the vessels there leak and bloddy noses and from the ears you eventually will see as they approach death.
Treatment is palliative care and support. And alot of crossing of fingers.