About what fraction of the world’s population has chronic diseases that are vector-borne?

• A. 1/4
• B. 1/2
• C. 3/4
• D. All

Answer: (B)

The main idea here is how widespread vector-borne diseases are and their long-term health effects. Vectors like mosquitoes, ticks, and sandflies reach many regions across the world, especially in tropical and subtropical areas. Diseases spread by these vectors—such as malaria, dengue, leishmaniasis, lymphatic filariasis, and Chagas—affect a large portion of people and often lead to chronic health issues, either through ongoing infections or lasting complications after the initial illness. Because these vectors are so widely distributed, roughly half of the world’s population lives in areas where vector-borne diseases are present and can contribute to chronic health problems. That makes about one-half a reasonable general estimate of global exposure and impact. The other options underestimate or overstate the reach, and saying all people are affected would be inaccurate.