Header Image

Mosquito-Borne Diseases

Table of Contents

Zika Virus

Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito. These are the same mosquitoes that spread dengue and chikungunya viruses.

  • These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They are aggressive daytime biters, prefer to bite people, and live indoors and outdoors near people.
  • Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.

About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika). The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week. The illness is usually mild with symptoms lasting for several days to a week. Zika virus usually remains in the blood of an infected person for a few days but it can be found longer in some people. Severe disease requiring hospitalization is uncommon and deaths are rare.

Zika virus is not currently found in the continental United States, but cases have been reported in returning travelers. Outbreaks of Zika have been reported in tropical Africa, Southeast Asia, the Pacific Islands, and most recently in the Americas. Because the mosquitoes that spread Zika virus are found throughout the world, it is likely that outbreaks will continue to spread.

The Alabama Department of Public Health advises pregnant women to consider postponing travel to areas where the Zika virus is being transmitted, including areas in South and Central America, as well as the American territories, including Puerto Rico. Infection with the Zika virus causes only mild symptoms in the majority of the cases, but an apparent link to birth defects and other pregnancy-related poor outcomes has been associated with infection during pregnancy. Out of an abundance of precaution, the ADPH is recommending that health care providers advise their patients who are pregnant about the risk of travel to these areas.

There have been recent reports that Zika virus is spread through blood transfusion and sexual contact. Rarely, the virus may spread from mother to child around the time of birth. It also may be possible to spread the virus from a mother to her baby during pregnancy. Specific recommendations provided by the Centers for Disease Control and Prevention (CDC) include the following:

  • Pregnant women should not travel to Zika-affected areas
  • Men who have traveled to Zika-affected areas and have pregnant partners should abstain from sex or consistently and correctly use condoms for the duration of the pregnancy for all forms of sexual activity.
  • Men who have traveled to Zika-affected areas and have non-pregnant partners should consider abstaining from sexual activity or consistently and correctly use condoms.

Testing should be performed on anyone who has a travel history to an infected area and is symptomatic. In addition, providers are asked to evaluate all pregnant women with a history of travel to countries with Zika virus transmission during pregnancy regardless of whether symptomatic or not. Because of the similar geographic distribution and clinical presentation of Zika, patients with symptoms consistent with Zika virus disease should also be evaluated for dengue and chikungunya virus infection.

Alabama physicians are asked to contact the ADPH Infectious Diseases & Outbreaks Division at 1-800-338-8374 if they have patients with a travel history and signs and symptoms consistent with Zika virus infection or pregnant women with a travel history whether symptomatic or not. Providers reporting patients with suspect Zika virus or pregnant women with a travel history to Zika endemic areas should call and request the Zika Virus Consultation Form.  All specimens submitted for testing must be approved by ADPH prior to submission.

Alabama Residents Tested for Zika Virus as of February 10, 2016

Number Tested Positive

Number of Submissions

Number with Results Pending




Zika Virus Resources

back to top


  • The Centers for Disease Control and Prevention (CDC) laboratory will test for chikungunya if the criteria are met byboth the CDC and ADPH for specimen submission. Testing will not be initiated without the inclusion of all requested and completed documentation. Requests and test results may be delayed.
  • The only private lab in the U.S. performing chikungunya testing is Focus Diagnostics. Focus Diagnostics has accounts with most large reference labs (i.e. Quest, LabCorp, Mayo, ARUP) and many local hospitals. In order to receive more timely results, providers can submit their chikungunya test request to a reference laboratory that has an account with Focus Diagnostics.
  • If a healthcare provider suspects a patient to have chikungunya with recent travel history (Southern Florida, Caribbean, Africa, Asia, Europe, India, or Pacific Ocean) please review the ADPH Chikungunya Recommendations, including reporting, patient education, specimen collection, shipping, and resources.

back to top

Dengue Fever and Dengue Hemorrhagic Fever

Dengue is a disease caused by any one of four closely related dengue viruses (DENV 1, DENV 2, DENV 3, or DENV 4). Dengue hemorrhagic fever (DHF) is a more severe form of dengue infection. It can be fatal if unrecognized and not properly treated in a timely manner. DHF is caused by infection with the same viruses that cause dengue fever. Dengue is transmitted to people by the bite of an Aedes aegypti or Aedes albopictus mosquito that is infected with a dengue virus. The mosquito becomes infected with dengue virus when it bites a person who has dengue virus in their blood. The person can either have symptoms of dengue fever or dengue hemorrhagic fever (DHF), or they may have no symptoms. After about one week, the mosquito can then transmit the virus while biting a healthy person. Dengue cannot be spread directly from person to person.

The principal symptoms of dengue fever are high fever, severe headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash, and mild bleeding (e.g., nose or gums bleed, easy bruising). Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms consistent with dengue fever. When the fever declines, symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing, may develop. This marks the beginning of a 24- to 48-hour period when the smallest blood vessels (capillaries) become excessively permeable (“leaky”). This may lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected. In addition, the patient with DHF has a low platelet count and hemorrhagic manifestations, tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding.

There is no vaccine for preventing dengue. The best preventive measure for residents living in areas infested with Ae. aegypti or Aedes albopictus is to eliminate the places where the mosquito lays her eggs, primarily artificial containers that hold water. Visit the Centers for Disease Control and Prevention (CDC) Traveler’s Health for information on travel notices to dengue endemic destinations.

Items that collect rainwater or to store water (for example, plastic containers, 55-gallon drums, buckets, or used automobile tires) should be covered or properly discarded. Pet and animal watering containers and vases with fresh flowers should be emptied and cleaned (to remove eggs) at least once a week. This will eliminate the mosquito eggs and larvae and reduce the number of mosquitoes present in these areas.

Using air conditioning or window and door screens reduces the risk of mosquitoes coming indoors. Proper application of mosquito repellents on exposed skin and clothing decreases the risk of being bitten by mosquitoes. To learn more about repellents, visit these CDC websites: Insect Repellent: Use and Effectiveness, Dengue, and Dengue: FAQs.

Dengue Fever Resources

back to top

West Nile Virus

West Nile virus (WNV) is an infectious disease agent that first appeared in the United States in 1999. WNV can result in an asymptomatic infection, a mild or moderate flu-like illness, or neurological diseases such as encephalitis or meningitis. Approximately 80 percent of people who are infected with WNV will show no symptoms at all. Typically people develop symptoms 3 to 14 days after they have been bitten by an infected mosquito.

Infectious Diseases & Outbreaks Division, Field Surveillance Staff (FSS), investigate all reports of West Nile disease from notifiable disease reporters. ADPH displays the confirmed cases on the Alabama Morbidity Report, Arbovirals, and submits it to CDC's ArboNet for display by county, see West Nile Alabama Cases links below. Case counts are updated weekly.

West Nile Virus Resources

Learn How To Reduce Your Exposure to Mosquitoes
Alabama Mosquito-Borne Cases from 2005 - 2015

For the General Public:
CDC West Nile Virus Homepage
CDC West Nile Fact Sheet (4 MB)
CDC Insect Repellent Use and Safety
Mosquito Myths from the University of Florida Medical Entomology Lab

For Healthcare Professionals:
CDC West Nile Virus Information and Guidance for Clinicians
CDC West Nile and Blood Transfusion and Organ Donation
CDC West Nile Statistics and Maps

For Veterinarians:
USDA West Nile Information

For Kids:
CDC Neato Mosquito - An Elementary Curriculum Guide on Mosquito Biology and the Prevention of La Crosse Encephalitis Virus infection
The Buzz-z-z on West Nile Virus

back to top

Footer Image