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West Nile Virus (WNV)



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September 2012

Beyond Hot Topic is an opportunity for viewers to submit questions to the Hot Topic presenter. The opportunity to submit questions for this topic is now closed.

The following questions were submitted by viewers and answered by the presenter, Bobbi Pritt, MD, Consultant in the Clinical Microbiology Division, Associate Professor of Laboratory Medicine and Pathology and Microbiology, and Director of the Clinical Virology and Parasitology Laboratory at Mayo Clinic in Rochester, MN.

Questions are presented as submitted (unedited).

  1. Immunity

    1. Would a person infected become immune to future infections?
    2. Would an infected individual become immune to future infections or would the disease lay dormant in the body and reoccur?
    3. Once a person contracts West Nile and recovers from it , are they immune to any chance of infection in the future or can West Nile still be infective and to what possible extent?
    4. If you have a positive IgM, how long will you be immune from reinfection of West Nile?

    I will answer all of these questions together: Infection with WNV confers lifelong immunity and there is little to no risk of reinfection.

  2. Are there any specific chemicals that can be sprayed in a yard to kill the mosquito larvae?

    There are products that will kill mosquito larvae (called ‘larvicides’). Mosquito larvae require water, so larvicides are usually applied directly to the water sources around the community. Larvicides can be biological (for example, bacterial toxins that kill the larvae) or chemical products, such as surface films to prevent the larvae from getting oxygen, insect growth regulators, and organophosphates.

    Larvicides are typically used as part of a comprehensive mosquito-control program, which includes surveillance (monitoring the levels of mosquito and virus activity), public education on the importance of applying insecticides before going outdoors, and selective use of chemicals to target mosquito adults and/or larvae.

  3. Is West Nile infection epidemic in other American countries?

    Yes, WNV is endemic in Europe, the Middle East, Africa, Australia, parts of Asia, and some regions in South America.

  4. Are there studies or trials on vaccinations?

    Yes, many researchers are working to create a vaccine for humans. There is hope that a vaccine will become available in the next few years.


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