Which virus is described as the leading cause of mosquito-borne disease and is often asymptomatic in most people?

• A. West Nile Virus
• B. Zika Virus
• C. Dengue Virus
• D. Malaria

Answer: (A)

West Nile Virus fits this description because it is a mosquito-borne virus that commonly infects people without causing noticeable illness. A large share of infections are asymptomatic or produce only mild, flu-like symptoms, which helps explain why it is considered the leading cause of mosquito-borne disease in many areas. The virus is transmitted by Culex mosquitoes that bite infected birds and then humans, with birds acting as the main reservoir. While most people don’t get seriously ill, a minority—often older individuals or those with weakened immune systems—can develop serious conditions like meningitis or encephalitis. This combination of being widespread and frequently asymptomatic is what makes West Nile Virus the best answer. Zika and dengue are also mosquito-borne but don’t have the same overall prevalence in many regions or the same typical asymptomatic pattern, and malaria is caused by a parasite, not a virus, so it doesn’t fit the description.