Which of the following is a preventive measure against West Nile Virus?

Using an approved insect repellent when going outside is a highly effective preventive measure against West Nile Virus. This virus is primarily transmitted to humans through the bite of infected mosquitoes. Therefore, employing insect repellent acts as a barrier to prevent mosquito bites, significantly reducing the likelihood of infection. Effective repellents typically contain ingredients such as DEET, picaridin, or oil of lemon eucalyptus, which have been proven to deter mosquitoes.

While other options might address different health concerns, they do not specifically target the transmission pathways of the West Nile Virus. Consuming boiled water, for instance, is important for preventing waterborne diseases but does not have any impact on mosquito-related transmission. Walking outdoors only during the day does not provide protection against mosquitoes, as some species that carry the virus can be active at different times, including dawn and dusk. Ignoring standing water can actually contribute to the problem since stagnant water is a breeding ground for mosquitoes, perpetuating the cycle of transmission. Thus, using insect repellent directly corresponds to preventing mosquito bites and thereby reducing the risk of contracting West Nile Virus.