The Most Common Mosquito-Borne Diseases

Malaria

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 occurring in Africa, Southeast Asia, and the Eastern Mediterranean.

Malaria is a serious blood infection caused by any of five different species of the Plasmodium parasite—falciparum, vivax, ovale, malariae,and knowles—which is spread by Anophelus mosquitoes.

Symptoms of malaria include:

• Intermittent episodes 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 to prevent malaria for those who are at risk.

There is a vaccine to prevent malaria that is being rolled out in sub-Saharan Africa. While its not incredibly effective, it is helpful at preventing severe disease in children and therefore has the potential to save hundreds of thousands or more lives.

West Nile Virus

West Nile virus has occurred throughout the world, but it is most commonly seen in the United States, especially in southern states.

The disease 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 an increased risk of severe illness. In rare cases, the infection can even lead to death.

Symptoms of severe West Nile virus infection include:

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

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 in someone who has the infection.

A person with West Nile virus is likely to recover without intervention. Treatment, when needed, is targeted to relieve symptoms. There is no antiviral treatment or vaccine for West Nile disease.

The Centers for Disease Control and Prevention (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.

Dengue Fever

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. It rarely is fatal; 4,032 deaths from dengue fever were recorded in 2015. It occurs in Africa, Southeast 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 pain 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.

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.

Chikungunya Disease

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 does not 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, including fluid and pain medication. There is no specific curative treatment or vaccination to prevent this illness.

The WHO recommends people at risk of chikungunya disease due to local outbreaks protect themselves from mosquito bites. Precautions include insect repellants and protective clothing.

Zika Virus

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

Symptoms of Zika virus infection include fever, rash, headache, 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 impair breathing to the point of being life-threatening.

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

St. Louis encephalitis

St. Louis encephalitis is caused by a flavivirus transmitted by mosquitoes of the Culex species. The illness is widespread in the Americas; in 2015, 23 cases were reported.

This infection rarely causes symptoms, but when it does, it 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. The vast majority of people infected are believed to improve slowly without treatment, but some people have prolonged side effects. There is a very low risk of death.

Yellow Fever

Yellow fever affects 200,000 people worldwide per year.

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

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

Symptoms of severe yellow fever include:

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

Diagnosing yellow fever can be challenging. However, a blood or urine test may be able to detect the virus in the early stages. Later, a test to identify antibodies may be necessary.

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