Still no mosquito-borne transmission in continental U.S.


Knoxville, Tenn. – The Knox County Health Department (KCHD) received laboratory confirmation today from the Tennessee Department of Health of Knox County’s first Zika virus case. The individual recently returned to the U.S. from an area overseas with active mosquito-borne transmission of Zika. The individual is expected to fully recover. As of July 20, 2016, 1,404 cases of Zika have been reported in the continental U.S. and Hawaii, including 14 in Tennessee. None of these have been the result of local spread by mosquitoes.


“We’ve been expecting a travel-associated case of Zika virus and believe more are likely as people travel to and from areas with active Zika transmission,” said KCHD Director Dr. Martha Buchanan. “It’s important for the public to know that we still have not seen local transmission in the continental U.S. However, it’s also crucial for the public to know that they play a major role in preventing local transmission by taking precautions to prevent mosquito bites and by eliminating mosquito habitats on their properties and at their businesses.”


Zika is spread primarily through the bite of an infected Aedes mosquito. These mosquitoes are aggressive daytime biters and they can also bite at night. Zika can also be transmitted through sexual contact. Most people infected with Zika do not become ill, and those who do become ill have mild symptoms that may include fever, rash, joint pain and conjunctivitis. No vaccine or medications are yet available to prevent or treat Zika. Symptoms are treated with plenty of rest, fluids and medicine to relieve fever and pain. Severe illness requiring hospitalization is uncommon, and deaths are rare.


“Just like with other diseases we monitor, our staff will work closely with any local Zika cases, including their family members and all individuals in the household, to prevent further spread of the virus,” said KCHD Deputy Director Mark Miller. “And in addition to our increased mosquito trapping and surveillance efforts, we will conduct door-to-door education in the community where the cases live per our emergency preparedness and response plan, which is in line with the Tennessee Department of Health.”


Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects. Until more is known, the Centers for Disease Control and Prevention (CDC) recommends that all pregnant women consider postponing travel to areas where Zika virus transmission is ongoing. Women who are pregnant or planning to become pregnant and must travel to these areas should first consult with their health care provider and take extra care to protect themselves from mosquito bites. Males who have traveled to affected countries should abstain from sexual activity or use condoms consistently and correctly for the duration of their partner’s pregnancy. All those who become ill after returning from areas with active Zika transmission should contact their medical provider.


Preventing mosquito bites, both at home and when traveling, is important to avoid the spread of disease. Tennessee is home to many types of mosquitoes, including the Aedes species, which are capable of transmitting several serious diseases. While mosquito transmission of Zika has not been documented in Tennessee, mosquitoes are known carriers of other diseases seen each year in the state, including West Nile virus and La Crosse encephalitis. They can also carry dengue fever, yellow fever and Chikungunya virus although not currently in Tennessee.


Officials recommend the following:

  • Apply repellants to skin often; these can include lotions, liquids or sprays. The CDC recommends the use of repellants that contain DEET, Picaridin, oil of lemon eucalyptus or para-menthane 3, 8-diol and IR3535. The duration of protection varies by repellant; read labels on products to determine when reapplications are necessary for optimal protection.
  • Wear long, loose and light-colored shirts and pants and wear socks.
  • Treat clothing with permethrin or purchase pretreated permethrin clothing.
  • Dispose of, regularly empty, or turn over any water holding containers on your property such as tires, cans, flower pots, children’s toys or trash cans.
  • Fill in hollow tree stumps and rot holes, a common breeding ground for the Aedes mosquito, with sand or concrete.
  • To prevent breeding in large water-holding devices, including bird baths or garden pools, use larvicides such as mosquito torpedoes or mosquito dunks. If used properly, larvicides will not harm animals.
  • Check the CDC’s travel webpage before traveling outside the U.S. because it’s important to be aware of the diseases impacting your destination(s), including those spread by mosquitoes, and take steps to prevent infection.


More information/resources:


Note: To protect privacy per federal law, KCHD will not release any further details on the individual case, including the area of Knox County in which he or she lives. International travel coupled with a location could aid in identification of the individual. This policy is in step with the Tennessee Department of Health.