A 32-year-old woman from Mumbai presents with fever, severe headache, and myalgia for 4 days. She reports that her 8-year-old son had similar symptoms 2 weeks ago, which resolved after 5 days. On examination, she has a petechial rash on her trunk and mild hepatomegaly. Platelet count is 85,000/μL, and NS1 antigen is positive. What is the most likely epidemiological classification of her dengue infection?