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Arbovirus

• Arboviruses (arthropod-borne viruses) are a large group of viruses that are spread mainly by blood-sucking insects. In the United States, arboviruses are most commonly spread by mosquitoes.
• Birds are often the source of infection for mosquitoes, which can then spread the infection to horses, other animals, and people.
• Most people infected with arboviruses have few or no symptoms, but arboviruses can cause serious and potentially fatal inflammation of the brain (encephalitis) as well as other complications.
• Prevention depends mainly on public health action to control mosquitoes and on individual action to avoid mosquito bites.

What is an arbovirus?

Arbovirus is short for arthropod-borne virus. Arboviruses are a large group of viruses that are spread by certain invertebrate animals (arthropods), most commonly blood-sucking insects. In the United States, arboviruses are spread mainly by mosquitoes. Birds are often the source of infection for mosquitoes, which can then transmit the infection to horses, other animals, and people. People are not an essential part of the life cycle for most arboviruses.

Where are arboviruses found?

Arboviruses are found throughout the world. The presence of an arbovirus in a particular area depends on the availability of specific types of mosquitoes that can carry it and specific birds or animals that can be infected.

What are arbovirus infections?

Arboviruses can cause four types of illness:

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• Illnesses of the central nervous system, ranging in seriousness from mild viral meningitis to encephalitis (inflammation of the brain), with coma, paralysis, and death
• Mild fever illnesses with or without rash
• Hemorrhagic fevers that can be serious and life-threatening
• Arthritis and rash, with or without fever

   

What are some important arbovirus infections?

More than 100 arboviruses cause disease in humans. Most of these are classified into groups, or families. Among the best known are: alphaviruses, flaviviruses, bunyaviruses, and reoviruses. Each causes specific types of illness. These are some examples.

Alphaviruses

• Eastern Equine encephalitis
• Western Equine encephalitis
• Venezuelan equine encephalitis

Flaviviruses

• St. Louis encephalitis
• Japanese encephalitis
• Yellow fever
• Dengue

Bunyaviruses

• LaCrosse encephalitis
• Reoviruses
• Colorado tick fever

   

What are the common signs and symptoms of arbovirus infections?

Most infected people have no symptoms. When symptoms occur, they usually start suddenly, with fever, chills, headache, muscle aches, and tiredness. In rare cases, infection can lead to encephalitis (inflammation of the brain). Symptoms of encephalitis are drowsiness, stiff neck, confusion, convulsions, tremors, and coma. Symptoms of hemorrhagic fever include signs of internal bleeding, which can lead to shock and sometimes death.

How soon after exposure do symptoms appear?

The time between exposure and symptoms can vary from 3 to 21 days.

What complications can result from arbovirus infections?

Complications of encephalitis can be serious, and include coma, permanent brain damage, and death.

How common are arbovirus infections?

Because people are not important in the life cycle of most arboviruses, arbovirus infections are generally rare in humans. When people are part of the natural cycle and are necessary for transmitting infection, such as for dengue and urban yellow fever viruses, then infection in people is more common. Most cases of arboviral encephalitis occur from June through September, when biting insects are most active. In mild parts of the country, cases can occur into the winter months.

Are arbovirus infections emerging infectious diseases?

Yes, many are increasing as people move into previously undeveloped areas where the viruses and their hosts live.

How can arbovirus infections be prevented?

Prevention centers mainly on public health action to control mosquitoes and on individual action to avoid mosquito bites. Community mosquito-control programs can reduce mosquito populations by applying pesticides and draining standing water. Individuals can avoid being bitten by mosquitoes by taking these prevention steps:

• If possible, stay inside between dusk and dark. This is when most types of mosquitoes are most active in their search for food.
• When outside in mosquito-infested areas, wear long pants and long-sleeved shirts.
• Spray exposed skin with an insect repellent.
• Screen homes to prevent mosquitoes from entering.
• Remove old tires and other water-holding containers from around homes. These can provide breeding sites for mosquitoes.

   

Vaccines are available for yellow fever and Japanese encephalitis.

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