Which of the following is a major factor contributing to the emergence of new infectious diseases?

• A. Widespread use of vaccines
• B. Increased international travel
• C. Improved sanitation practices
• D. Decreased human population density

Answer: (B)

Verified step by step guidance

1. Understand the concept of 'emergence of new infectious diseases,' which refers to the appearance of new infections in a population or the rapid increase in incidence or geographic range of a disease.
2. Consider how human behaviors and environmental changes influence the spread and evolution of infectious agents.
3. Evaluate each option by thinking about its impact on disease transmission: widespread use of vaccines generally reduces disease spread; improved sanitation also reduces infection rates; decreased human population density tends to lower transmission opportunities.
4. Focus on 'increased international travel' as it facilitates the rapid movement of people and pathogens across the globe, allowing diseases to spread to new regions and populations quickly.
5. Conclude that increased international travel is a major factor contributing to the emergence and global spread of new infectious diseases due to enhanced connectivity and exposure.