Common Questions About West Nile Virus

  1. What is West Nile virus?
    West Nile virus causes a disease that is usually transmitted to humans by the bite of an infected mosquito. Thousands of people in Colorado were infected with West Nile virus in 2003. Sixty-three people died. Many people who became seriously ill are continuing to recover while others suffered permanent disabilities.
  2. Is West Nile virus still a threat in Larimer County?
    Yes, West Nile Virus is here to stay in Colorado and Larimer County. Although the seasons following 2003 have had less human cases reported, West Nile virus is now considered to be permanent in Colorado and infections can be expected each year. Infected mosquitoes have been trapped in Larimer County each year since 2003.
  3. Who is most likely to get West Nile disease?
    People of any age who spend a lot of time outdoors are more likely to be bitten by an infected mosquito and therefore develop West Nile disease. People over 50 years of age and those who have serious diseases and immune disorders are more likely than younger patients to have the most severe forms of the disease. Those who have received organ transplants and people receiving chemotherapy are also at high risk for severe disease.
  4. What are the symptoms of West Nile virus?
    West Nile virus infections cause a variety of symptoms in humans which commonly include: fever, headache, body aches, tiredness, skin rash on the trunk of the body, swollen lymph glands, nausea or vomiting. Signs of illness appear suddenly from 3 - 14 days after a person is bitten by an infected mosquito. Approximately 1 out of 5 people bitten by an infected mosquito develop West Nile Fever or even more severe forms of the infection such as West Nile Meningitis, Encephalitis, and Poliomeyelitis.
  5. What can I do to prevent West Nile virus infection?
    The best way to avoid West Nile virus is to prevent mosquito bites. Stay indoors if possible, during peak mosquito biting hours (generally from dusk to early dawn; sunset to 1.5 hours after sunset appear to be the most active "feeding time" for the species that carry West Nile virus).

    When you are outdoors, use a mosquito repellent. Those containing DEET are the most effective and long-lasting and most thoroughly tested. The Centers for Disease Control and Prevention (CDC) has added two plant-based mosquito repellents to the list of safe and effective products. These include repellents containing picaridin, or oil of lemon eucalyptus.
  6. Do I have to wear repellent if I will only be outdoors for a short time?
    Your backyard or patio is not a "safe zone." Even a brief trip out to the barbecue, mailbox or garden allows time for an infected mosquito to bite. During the peak WNV season (mid-June through August) infected mosquitoes can be found all along the Front Range so use repellent where you live, work and recreate.
  7. Can my pets get West Nile virus?
    Dogs, cats, birds, horses, alpacas and other domestic pets can get West Nile virus from mosquito bites. Dead birds do not infect pets that come into contact with them. If a pet is infected with WNV, most will not become ill or show only mild symptoms and are expected to fully recover from the disease. West Nile virus infections in unvaccinated horses may cause severe symptoms and up to one-third of unvaccinated horses die. There is no documented WNV transmission from pet animals to humans.
  8. How can I protect my horses from West Nile virus?
    Horses require 2 vaccinations within a three to six week period to prevent infection. Previously vaccinated horses require one booster shot annually. Please speak with your veterinarian regarding the specifics of the vaccination
  9. When is my DEET product too old to use?
    DEET is very stable and is effective indefinitely as a repellent. For this reason, the federal government doesn't require an expiration date on product labels. But manufacturers of repellents say that the feel, smell and appearance of their products may change after about three years. This does not reduce the DEET's ability to repel mosquitoes and ticks but may make the product less appealing to users. If you're not sure about your particular product, contact the manufacturer.