This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
According to International Health Regulations, there is no risk of spread of yellow fever if the Aedes aegypti index remains below: 
Select and explain. 
A. 1%, B. 5%, C. 8%, D. 10%
A: 1%
Answer: A: 1% 
Explanation: 1%