Maricopa County Maricopa County | Site Map | Search | Phone Directory | Departments | Services
corner image corner image
Maricopa County Public Health logo
A to Z Index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Mosquito-Related Diseases


Yes, Maricopa County does have mosquitoes and at times, we have high numbers of the blood suckers. Unfortunately, with our mosquitoes have come mosquito-related diseases. The best thing each of us can do to protect ourselves and our families from these diseases is to prevent getting bit by mosquitoes and to eliminate breeding sites on our own property.

Zika Virus (pronounced Zee-Ku) is:

  • a virus that is spread through mosquito bites - the same Aedes mosquitoes that can spread dengue and chikungunya.

  • a risk to anyone traveling to a region where Zika virus is found.

Signs & Symptoms

Approximately 1 in 5 people infected with Zika virus will become ill. Symptoms usually begin within a few days to two weeks after being bitten by an infected mosquito.

The principal symptoms are:

  • fever
  • rash
  • joint pain
  • Conjunctivitis (red eyes)

Other less common symptoms may include:

  • muscle pain
  • headache
  • pain behind the eyes
  • vomiting

Zika virus infection during pregnancy may lead to birth defects such as microcephaly (smaller than normal head size in infants due to incomplete brain development).

Helpful Links & Materials

Chikungunya (pronunciation: \chik-en-gun-ye) is:

  • a virus that is spread through mosquito bites - the same Aedes mosquitoes that spread dengue.

  • a risk to anyone traveling to a region of the world where chikungunya is found.

Signs & Symptoms

Symptoms usually begin 3-7 days after being bitten by an infected mosquito.

  • fever and severe joint pain, often in the hands and feet

  • headache

  • muscle pain

  • joint swelling

  • rash

Most patients will feel better within a week. Some people develop longer-term joint pain that can last weeks to months. Death is rare but can occur.

People at increased risk for severe disease include:

  • newborns exposed during delivery,

  • older adults (≥65 years),

  • people with medical conditions such as high blood pressure, diabetes, or heart disease.

Helpful Links & Materials

Dengue (pronounced den' gee) is:

  • a virus that is spread through mosquito bites - the same Aedes mosquitoes that can spread chikungunya.

Signs & Symptoms

The principal symptoms of dengue are:

  • High fever and at least two of the following:
    • Severe headache

    • Severe eye pain (behind eyes)

    • Joint pain

    • Muscle and/or bone pain

    • Rash

    • Mild bleeding manifestation (e.g., nose or gum bleed, petechiae, or easy bruising)

    • Low white cell count

Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Watch for warning signs as temperature declines 3 to 7 days after symptoms began.

Go IMMEDIATELY to an emergency room or the closest health care provider if any of the following warning signs appear:

  • Severe abdominal pain or persistent vomiting
  • Red spots or patches on the skin
  • Bleeding from nose or gums
  • Vomiting blood
  • Black, tarry stools (feces, excrement)
  • Drowsiness or irritability
  • Pale, cold, or clammy skin
  • Difficulty breathing

Helpful Links & Materials

West Nile Virus (WNV) is:

  • an infection that can cause serious disease. WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall.

  • it is spread by the bite of an infected mosquito. Mosquitoes become infected by feeding on infected birds. In a very small number of cases, WNV has also been spread directly from an infected person through blood transfusions, organ transplants, breastfeeding and during pregnancy from mother to baby.

Signs & Symptoms

No symptoms in most people. Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.

Febrile illness in some people. About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Severe symptoms in a few people. Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues).

  • The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.

  • People with certain medical conditions, such as cancer, diabetes, hypertension and kidney disease are also at greater risk for serious illness.

  • Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent.

  • About 10 percent of people who develop neurologic infection due to West Nile virus will die.

Helpful Links & Materials

St. Louis Encephalitis (SLEV) is:

a rare disease that is caused by a virus spread by infected mosquitoes. SLEV is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain (encephalitis).

Signs & Symptoms

Many persons infected with SLEV have no apparent illness. People with mild illness often have only a headache and fever.

More severe disease is marked by:

  • fever

  • headache

  • neck stiffness

  • stupor

  • disorientation

  • coma

  • tremors

  • occasional convulsions (especially in infants)

  • spastic (but rarely flaccid) paralysis.

The risk of severe disease generally increases with age.

Helpful Links & Materials