This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'True about HIV epidemiology - \nSelect and explain. \nA. Children rarely affected, B. <10% of HIV infected person progress to AIDS, C. Southern africa have 72% of total global burden, D. Seminal secretion is more infectious than vaginal secretion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Key facts about Epidemiology of HIV infection Reservoir: Cases and carriers Source: Virus is in greatest concentration in blood, seen and CSF (Lower concentrations in tear, saliva, breast milk, urine, cervical and vaginal secretions) Children under 15 years make only 3% cases Basic modes of transmission Sexual Blood and blood products Neddles/syringes Mother to child transmission (MTCT) Incubation period : few months to 10 years Ref: Park 25th edition Pgno : 363-367', 'role': 'assistant'}]