Common Diseases Carried by Mosquitoes

An image of a mosquito
As well as being a pest, mosquitoes can carry numerous diseases that can make people and animals sick.
39 species of mosquitos have been found in Brownsville, and not all mosquitoes carry diseases. Of concern are Aedes Aegypti, Aedes Albopictus, Aedes Triseriatus, Culex Pipiens, Culex Quinquefasciatus, Culex Nigripalpus, Culex Tarsalis, Culex Tritaeniorhynchus, Anopheles Freeborni and Culiseta Melanura. 

 The following are the most common diseases found nationwide.

Zika Virus 

“Zika is the first mosquito-transmissible virus that has been shown to cause birth defects, and the first mosquito-borne sexually transmitted disease or infection.” 

Zika infection during pregnancy can cause a birth defect of the brain called microcephaly and other severe brain defects. It is also linked to other problems, such as miscarriag​e, stillbirth, and other birth defects. There have also been increased reports of Guillain-Barré syndrome, an uncommon sickness of the nervous system, in areas affected by Zika.

  • Zika is spread mostly by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). These mosquitoes bite during the day and night.
  • Zika is sexually transmitted.  Man to Female, Male to Male, Female to Female. 
  • Zika can be passed from a pregnant woman to her fetus. Infection during pregnancy can cause certain birth defects.
  • There is no vaccine or medicine for Zika.

Many people infected with Zika virus won’t have symptoms or will only have mild symptoms. The most common symptoms of Zika are

  • Fever
  • Rash
  • Headache
  • Joint pain
  • Red eyes
  • Muscle pain

ONLY 1 out 5 people will show these symptoms.
Symptoms can last for several days to a week. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. Once a person has been infected with Zika, they are likely to be protected from future infections.

West Nile Virus

West Nile virus (WNV) has been in the United States since 1999, and as been seen in Texas since 2002. West Nile virus is spread to human through a single mosquito bite. WNV is a blood-borne disease, there has not been any cases of a person contracting the virus through everyday contact with an infected individual. Although, there are records of people contracting the disease through organ transplants and blood transfusions.

There are three different gradations of WNV:
  • West Nile Virus
  • West Nile Fever
  • West Nile Nuroinvasive Disease
Most of the public who contract WNV (about 80%) will never show any symptoms, this gradation of the virus is referred to as West Nile virus.

About 20% of the population that contracts the virus will contract West Nile fever. Symptoms of this include fever, headache, nausea, and possible rash. These symptoms are very similar to flu-like symptoms, and many people who contract West Nile fever think they have the flu.

The more severe cases of West Nile (WN) are the neuroinvasive diseases. These can include encephalitis, meningitis, and mengioencephalitis. This gradation of the virus can lead to stroke-like symptoms, coma, paralysis and even death. About 1% of the population that contracts WN will get these more sever symptoms. To read more on West Nile Virus please visit the Texas Department of State Health Services website.


There are various forms of viral encephalitis transmitted by mosquitoes West Nile, St. Louis, Japanese, La Crosse, Western Equine and Eastern Equine. All are carried by wild birds, most of which show no symptoms. Infected birds are then bitten by local mosquitoes that can pass the virus on the human through future bites. Symptoms of encephalitis range from mild flu-like illness to severe brain inflammation that can cause death. West Nile virus, Western and Eastern Equine encephalitis can affect horses and other animal as well as humans. For more information please Texas Department of State Health Services website.


Malaria is much less likely to occur in Cameron County, due to the necessity for human reservoirs of the disease. Anoplheles mosquitoes, the vectors of malaria, are found in some areas of Texas, and there have been isolated instances where human reservoirs from other countries temporarily provided a source of malaria infection to local residents. For FAQs visit the Texas Department of State Health Services website.


Dengue (déng gee, déeg gáy) is a mosquito-borne infection which in recent years has become a major international public health concern. Dengue is found in tropical and sub-tropical regions around the world, predominately in urban and Peri-urban areas.

Dengue hemorrhagic fever (DHF), a potentially lethal complication, was first recognized during the 1950s, and today is a leading cause of childhood mortalities in several Asian countries. There are four distinct, but closely related, viruses which cause dengue. Recovery from infection by one provides life long immunity against that sero-type but confers only partial and transient protection against subsequent infection by the other three. Indeed, there is good evidence that sequential infection increases the risk of more serious disease resulting in DHF. For more information please visit the Texas Department of State Health Services website and view an article about Dengue (PDF).

Yellow Fever


Initial symptoms include fever, loss of appetite, headache, vomiting, and backache. As the disease progresses, the pulse slows and weakens. After three to four days, most patients improve and their symptoms disappear. However, about 15% of cases enter a "toxic phase within 24 hours. This phase is characterized by bleeding of the gums and bloody urine, and can progress to delirium, seizures, and coma. Jaundice can also occur relatively early in the disease, thus the name "yellow fever.“

Last outbreak in 1867 Galveston area.