Which statement about Yellow Fever is correct?

• A. Not transmitted by mosquitoes
• B. Human vaccine available but with some adverse side effects
• C. Last U.S. epidemic in 1905
• D. It is not transmitted by humans or mosquitoes

Answer: (B)

Yellow fever knowledge hinges on how it spreads and how we prevent it. The virus is carried by mosquitoes, mainly Aedes aegypti in urban settings, and humans can be bitten and become infected, helping sustain transmission in at-risk areas.

The statement about a human vaccine being available but with some adverse side effects is the best answer because there is an effective live-attenuated yellow fever vaccine in use that provides strong protection. Like many vaccines, it carries a risk of adverse events for a small number of recipients. Most people have only mild, short-lived reactions, but rare serious events can occur (for example, severe vaccine-associated adverse outcomes). This nuance—highly protective vaccine with occasional adverse effects—captures the real-world balance of yellow fever prevention.

The other statements aren’t correct. Yellow fever is transmitted by mosquitoes, so saying it is not transmitted by mosquitoes is false. The idea that it’s not transmitted by humans or mosquitoes is also false because humans can become infected and mosquitoes transmit the virus between people. As for the historical note, while there was a major epidemic in the United States in the early 1900s, that does not reflect current control and prevention practices, and the key point for public health today is the existence and safety profile of the vaccine.