What is Arboviruses

What is Arboviruses (Symptoms, Causes, Test and Treatment)

Arbovirus is a term used to describe a group of viral infections transmitted to humans by a group of insects known as arthropods. There are many strains of arboviruses. We shall discuss it like (Symptoms, Causes, Test and Treatment. Arboviruses are caused by insect bites in the arthropod family. This can include ticks, mosquitoes and fleas. You can read more about Infectious diseases here

Types of arbovirus:

There are many types of arboviruses. The different types of arboviruses are divided into specific genera.

There are  three main types of genera for arboviruses that cause infections in humans are as follows:

  • bunyavirus
  • flavivirus
  • togavirus

 

Overview:

More than 100 arthropod-borne viruses (arboviruses) are known to cause human disease. Although most infections are subclinical, the symptomatic illness usually manifests as 1 of 3 primary clinical syndromes: generalized febrile illness, neuroinvasive disease, or hemorrhagic.

Clinical Manifestations for Select Domestic and International Arbleoviral Diseases Tab
Clinical Manifestations for Select Domestic and International Arboviral Diseases

Generalized feverish illness:

 Most arboviruses can cause a systemic febrile illness that often includes headache, arthralgia, myalgia, and rash. Some viruses can cause more characteristic clinical manifestations, such as focal neurologic defects (Chapter 163, West Nile Virus), severe polyarthralgia, or jaundice (eg, Yellow Fever Virus). With some arboviruses, fatigue, malaise, and weakness can persist for weeks after the initial infection.

Neuroinvasive disease:

Many arboviruses cause neuroinvasive diseases, such as aseptic meningitis, encephalitis, or acute flaccid myelitis. The disease usually presents with a prodrome similar to systemic febrile illness followed by neurological symptoms. The Specific symptoms vary by virus, but can include vomiting, stiff neck, changes in mental status, seizures, or focal neurological deficits.

West Nile virus can cause acute flaccid myelitis syndrome, either in conjunction with meningoencephalitis or as an isolated finding. The full range of neurological manifestations of Zika virus is unclear. The severity and long-term outcome of the disease vary depending on the etiologic agent and underlying characteristics of the host, such as age, immune status, and pre-existing medical condition.

Hemorrhagic fever:

Hemorrhagic fevers can be caused by dengue or yellow fever viruses. After several days of nonspecific febrile illness, the patient may develop overt signs of bleeding (eg, Petechiae, ecchymosis, bleeding from the nose and gums, hematemesis, and melena) and shock (eg, decreased blood pressure). peripheral circulation, azotemia, tachycardia and hypotension).

Hemorrhagic fever and shock caused by yellow fever viruses have a high mortality rate and can be confused with rodent-borne hemorrhagic fevers (eg, Argentine hemorrhagic fever, Bolivian hemorrhagic fever, and Lassa fever) or Lassa fever. caused by the Ebola or Marburg viruses. Although dengue can be associated with severe bleeding, shock is primarily attributed to a capillary leak syndrome which, if properly treated with fluids, can result in a high rate of recovery.

Cause of Arboviruses:

Arboviruses are RNA viruses that are transmitted to humans primarily through the bites of infected arthropods (mosquitoes, ticks, sand flies, and biting mosquitoes. The viral families responsible for most arbovirus infections in Humans are Flaviviridae (genus Flavivirus), Togaviridae (genus Alphavirus), and Bunyaviridae (genus Orthobunyavirus and Phlebovirus). Reoviridae (genus Coltivirus) are also responsible for fewer human arbovirus infections.

Epidemiology:

Most arboviruses maintain transmission cycles between birds or small mammals and arthropod vectors. Humans and domestic animals are generally infected incidentally as “dead” hosts (see Table 6.2). Important exceptions are dengue, yellow fever, chikungunya, and the Zika virus, which can be transmitted from person to arthropod to person (anthroponotic transmission). In the case of other arboviruses, humans often do not develop a sufficiently high or sustained level of viremia to infect biting arthropod vectors. Direct person-to-person transmission of arboviruses can occur through blood transfusions, organ transplants, sexual transmission, intrauterine transmission, perinatal transmission, and breast milk.

Tabble for arboviral diseases
Genus, Geographic Location, Vectors, and Average Number of Annual Cases Reported in
the United States for Selected Domestic and International Arboviral Diseases

 

Transmission through percutaneous, mucosal, or aerosol exposure to some arboviruses has occurred rarely in workplace and laboratory settings. In the United States, arbovirus infections occur primarily from late spring to early fall, when mosquitoes and ticks are most active. The number of reported domestic or imported arboviral disease cases in the United States varies widely by specific etiology and year. Underreporting and underdiagnosis of milder diseases make it difficult to determine the actual number of cases. In general, the risk of serious clinical illness for most arbovirus infections in the United States is higher in adults than in children. A notable exception is La Crosse virus infection, for which children are at increased risk of severe neurological disease and possible long-term sequelae. Eastern equine encephalitis virus causes a low incidence of the disease but a high case fatality rate (40%) in all age groups.

Incubation periods for arboviral diseases typically range from 2 to 15 days. Longer incubation periods can occur in immunosuppressed individuals and for tick-borne viruses such as tick-borne encephalitis and Powassan viruses.

Diagnosis & Tests:

Arboviral infections are most often confirmed by detection of virus-specific antibodies in serum or cerebrospinal fluid (CSF). Acute phase serum samples should be tested for virus-specific immunoglobulin (Ig) M antibodies. With clinical and epidemiological correlation, a positive IgM test result has good diagnostic predictive value, but a cross-reaction with related arboviruses of the same viral family (e.g., West Nile and St. Louis, which are both flaviviruses). For most arbovirus infections, IgM is detectable 3 to 8 days after disease onset and persists for 30 to 90 days, but longer persistence has been documented, especially with West Nile virus. Therefore, a positive serum IgM test result can sometimes reflect a previous infection. Serum collected within 10 days of illness onset may not have detectable IgM, and the test should be repeated on a convalescent specimen. IgG antibody is generally detected in serum shortly after IgM and persists for years.

A plaque reduction neutralization test can be performed to measure virus-specific neutralizing antibodies and to discriminate between cross-reactive antibodies in primary arbovirus infections. Seroconversion or a four-fold or greater increase in virus-specific neutralizing antibodies can be used between acute and convalescent serum samples collected 2 to 3 weeks apart to confirm recent infection. In patients who have been immunized or infected with another arbovirus of the same virus family in the past (i.e., a secondary infection), cross-reactive antibodies in IgM and neutralizing antibody assays can make it difficult to identify which arbovirus is causing the infection. patient’s illness. For some arbovirus infections (eg, Colorado tick fever), the immune response may be delayed, with IgM antibodies not appearing until 2 to 3 weeks after disease onset and neutralizing antibodies taking up to a month to develop. With significant immunosuppression (eg, patients who have received a solid organ transplant or recent chemotherapy) may have a delayed or attenuated serological response.

When interpreting results, vaccination and travel history, date of onset of symptoms, and information on other arboviruses known to circulate in the geographic area and which may be cross-reactive in serological tests should be considered. Viral Culture and Nucleic Acid Amplification Testing (NAAT) for RNA can be performed on serum, CSF, or acute phase tissue samples.

Arboviruses that are most likely to be detected by culture or NAAT in the early stages of the disease include Colorado tick fever, dengue fever, yellow fever, and Zika viruses. For other arboviruses, the results of these tests are often negative even early in the clinical course due to the relatively short duration of viremia. Immunohistochemical (IHC) staining can detect specific viral antigens in fixed tissue. Antibody tests for common household arboviral diseases are performed in most state public health laboratories and in many commercial laboratories. Confirmatory tests for plaque reduction neutralization, viral culture, NAAT, immunohistochemical staining, and tests for less common national and international arboviruses are performed at the Centers for Disease Control and Prevention (CDC; phone: 970-221-6400). and other selected reference laboratories. Confirmatory tests are generally arranged through state and local health departments.

Treatment of Arboviruses:

The primary treatment for all arboviral diseases is supportive. Although various antiviral and immunologic therapies have been evaluated for several arboviral diseases, none have shown clear benefits.

People who develop symptoms of an arbovirus should seek a diagnosis to ensure that they receive proper treatment and that public health problems are recorded.

A doctor will check to see if a person with suspected arbovirus meets certain clinical criteria. Clinical criteria differ depending on whether or not the arbovirus is neuroinvasive or non-neuroinvasive.

 

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