The Most Common Mosquito-Borne Diseases

Mosquito bites are not usually dangerous, but some mosquitoes spread diseases like malaria and West Nile fever. Mosquitos cause diseases by biting a person and depositing an infectious organism into their body, like a virus or a parasitic egg.

Not all mosquitos carry disease, and different species of mosquitos carry different diseases. While your risk of catching a disease from a mosquito bite can be very low in some regions, you could be at higher risk in certain areas or at specific times of the year. Taking steps to prevent mosquito bites can help you avoid catching a mosquito-borne illness.

Habitat Preferences

Mosquitos need a certain temperature, foliage, and water supply to survive. Each mosquito species is able to thrive—and transmit disease—in its own habitat.

For example, Culex pipiens, the mosquito species that spread West Nile, live in stagnant, polluted, and dirty water. And Anopheles mosquitos, which transmit malaria, survive near permanent water sources, such as lakes, ponds, and swamps.

In contrast, Aedes aegypti, which transmits the Zika virus, dengue, and chikungunya, is a floodwater mosquito that can breed in relatively small amounts of water, including small containers. Aedes aegypti can thrive in urban areas, which is why the Zika virus disease has been identified in wet, damp, heavily populated environments like those of Brazil.



Anopheles Mosquito

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Worldwide, malaria is the most widespread mosquito-borne illness. According to the World Health Organization (WHO), malaria is responsible for approximately 405,000 deaths a year, with most cases of malaria occurring in Africa, Southeast Asia, and the Eastern Mediterranian.

Malaria is a serious blood infection caused by any of four different species of the Plasmodium parasite, which is spread by Anophelus mosquitoes.

Common symptoms of malaria include:

  • Intermittent attacks of fever, sweating, and chills
  • Headache
  • Vomiting
  • Myalgia (muscle pain)

Complications include hemolytic anemia (bursting of red blood cells), thrombocytopenia (destruction of platelets), and splenomegaly (enlarged spleen). Severe malaria infections cause life-threatening organ damage.

Malaria is diagnosed based on a microscopic examination of a blood sample, which can identify the parasitic organism.

Antimalarial drugs, including chloroquine and hydroxychloroquine, are used to treat malaria. Some antimalarial drugs can also be used as prophylaxis to prevent malaria for those who are at risk. There is no vaccine available to prevent the infection.


West Nile Virus

Culex Pipiens mosquito on a person's arm

 Seraficus / Getty Images

West Nile disease has been described worldwide, but it is most commonly seen in the US, especially in southern states. It is the most common mosquito-borne illness in the US.

West Nile disease, also called West Nile fever, is caused by an infection with the West Nile virus, which is transmitted by the Culex pipiens mosquito.

Most people infected with West Nile virus either don't experience any effects or develop mild symptoms, including fever, vomiting, diarrhea, rash, and generalized aches and pains.

Older adults are at a higher risk of severe illness. And rarely, the infection can even lead to death.

Symptoms of severe West Nile disease include:

  • High fevers
  • Neck stiffness
  • Convulsions
  • Muscle weakness
  • Disorientation

While this disease is associated with birds (mosquitos spread it from birds to humans), it shouldn't be mistaken for bird flu, which is a different condition.

Diagnosis of West Nile virus infection involves blood tests that can identify the virus or its antibodies. But the virus and antibodies can be undetectable even if you have the infection.

You are likely to recover without any intervention. Treatment, when needed, is symptomatic and supportive. There is no antiviral treatment or vaccine for West Nile disease.

The CDC recommends preventing the disease with environmental mosquito control measures and personal protection from mosquito bites. This is especially important in summer and fall in areas where the disease is known to be prevalent.



Aedes aegypti

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Dengue fever is an infection caused by the dengue virus and spread by the Aedes aegypti mosquito and the Asian tiger mosquito (Aedes albopictus). This infection affects almost 300 million people per year, but it is rarely fatal, with 4,032 deaths recorded in 2015. It occurs in Africa, South-East Asia, South America, and the Western Pacific.

Dengue fever causes high fevers, a rash, and headaches. The infection can also cause severe muscle, joint, and bone pains. This pain can be so intense that dengue fever has been called "breakbone fever."

Diagnosis involves blood tests that can identify the virus or its antibody. There is no cure or antiviral therapy for dengue fever. It is treated with supportive care and symptom management.

Most people with dengue fever recover, but some go on to develop dengue hemorrhagic fever, which can be deadly. Medical care in these instances includes intravenous fluids and blood transfusions.

A dengue vaccine is available, but it is not recommended for everyone who is at risk of the infection. When someone is exposed to the virus after having been vaccinated, there is an increased risk of severe dengue. Therefore the WHO recommends the vaccine only for people who already have antibodies to the dengue virus.



Asian Tiger Mosquitos

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Chikungunya virus can be transmitted by both Aedes aegypti and Aedes albopictus. The disease caused by the virus occurs in warm climates throughout the world, including Africa, India, and parts of the Caribbean and South America, affecting between 100,000 and 200,000 people worldwide per year.

It often doesn't cause symptoms, and it can cause a mild-self limited illness characterized by fevers, headaches, a rash, and joint aches and pains. However, in some cases, the aches and pains persist for several years.

Chikungunya disease is managed with supportive treatment, like fluids and pain medications. There is no specific curative treatment or vaccination to prevent this illness.

The WHO recommends that people who are at risk due to local outbreaks protect themselves from mosquito bites. Precautions include insect repellants and protective clothing.


Zika Virus

Aedes aegypti zika mosquito
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Zika virus is primarily spread by Aedes aegypti. The illness had been rarely identified in Asia and Africa and it became more widely recognized when an outbreak of the infection occurred in Brazil in 2015 

Symptoms of Zika virus infection include fevers, a rash, headaches, and joint pain. This infection generally improves on its own, but it can cause microcephaly (a small head and underdeveloped brain) and other birth defects in babies born to infected mothers.

Additionally, Zika virus infection can lead to Guillan barre syndrome, an acute nerve disease that can be life-threatening due to impaired breathing.

Zika virus is diagnosed with blood tests that can identify the virus or its antibodies. And there is no cure for the condition—it is treated symptomatically.


St. Louis encephalitis

St. Louis encephalitis is caused by a flavivirus transmitted by mosquitos of the Culex species. The illness primarily occurs in the US, where it has been reported throughout the country, affecting less than 20 people per year since 2009.

This infection affects the brain and can cause dizziness, headaches, nausea, and confusion. It is diagnosed with a blood test or lumbar puncture sample of cerebrospinal fluid, which may identify the virus or antibodies to the virus.

There is no specific treatment or vaccination for St. Louis encephalitis, and the vast majority of those infected are believed to improve slowly without treatment, but some people have prolonged effects and there is a very low risk of death.


Yellow Fever

Print of Panama Canal Construction c. 1890

Print Collector / Contributor / Getty Images

Yellow fever is rare in the US and uncommon worldwide, but it does occur.

This disease, which is most prevalent in Africa and South America, is caused by a the arbovirus flavivirus, a virus spread by the Aedes aegypti mosquito.

Symptoms of yellow fever can be mild, causing a flu-like illness with fevers, chills, and headaches that improve without specific treatments. But a severe illness, which affects approximately 15% of those infected, can result in death.

Symptoms of severe yellow fever illness include:

  • Jaundice (yellow discoloration of the eyes and skin)
  • Persistent fevers
  • Dark urine
  • Vomiting or vomiting blood (which can look dark red or black)
  • Seizures
  • Arrhythmias (irregular heart rhythm)
  • Shock
  • Coma

Yellow fever is diagnosed based on several tests, such as a urine test that can identify blood or protein, or a blood or urine test used to detect the virus.

Treatment for yellow fever is focused on symptomatic management with fluids and medications for control of fever and pain relief. There is no specific antiviral medication.

Vaccination is recommended for the prevention of yellow fever for people who live in or are traveling to an endemic region.

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Article Sources
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