Clinical microbiology of the dengue virus

These dengue viruses are single-stranded RNA viruses that belong to the family Flaviviridae and the genus Flavivirus—a family which includes other medically important vector-borne viruses e.

Clinical microbiology of the dengue virus

Laboratory diagnosis methods for confirming dengue virus infection may involve detection of the virus, viral nucleic acid, antigens or antibodies, or a combination of these techniques.

After the onset of illness, the virus can be detected in serum, plasma, circulating blood cells and other tissues for 4—5 days.

During the early stages of the disease, virus isolation, nucleic acid or antigen detection can be used to diagnose the infection.

Dengue fever

At the end of the acute phase of infection, serology is the method of choice for diagnosis. Antibody response to infection differs according to the immune status of the host 1.

When dengue infection occurs in persons who have not previously been infected with a flavivirus or immunized with a flavivirus vaccine e. IgM antibodies are the first immunoglobulin isotype to appear.

IgM levels peak about two weeks after the onset of symptoms and then decline generally to undetectable levels over 2—3 months. Anti-dengue serum IgG is generally detectable at low titres at the end of the first week of illness, increasing slowly thereafter, with serum IgG still detectable after several months, and probably even for life 2 — 4.

During a secondary dengue infection a dengue infection in a host that has previously been infected by a dengue virus, or sometimes after non-dengue flavivirus vaccination or infectionantibody titres rise rapidly and react broadly against many flaviviruses. The dominant immunoglobulin isotype is IgG which is detectable at high levels, even in the acute phase, and persists for periods lasting from 10 months to life.

Early convalescent stage IgM levels are significantly lower in secondary infections than in primary ones and may be undetectable in some cases, depending on the test used 5. A range of laboratory diagnostic methods has been developed to support patient management and disease control.

Dengue: Guidelines for Diagnosis, Treatment, Prevention and Control: New Edition.

The choice of diagnostic method depends on the purpose for which the testing is done e. In general, tests with high sensitivity and specificity require more complex technologies and technical expertise, while rapid tests may compromise sensitivity and specificity for the ease of performance and speed.

Virus isolation and nucleic acid detection are more labour-intensive and costly but are also more specific than antibody detection using serologic methods. Comparison of diagnostic tests according to their accessibility and confidence.

Clinical management Dengue virus infection produces a broad spectrum of symptoms, many of which are non-specific. Thus, a diagnosis based only on clinical symptoms is unreliable.

Early laboratory confirmation of clinical diagnosis may be valuable because some patients progress over a short period from mild to severe disease and sometimes to death. Early intervention may be life-saving. Before day 5 of illness, during the febrile period, dengue infections may be diagnosed by virus isolation in cell culture, by detection of viral RNA by nucleic acid amplification tests NAATor by detection of viral antigens by ELISA or rapid tests.

Virus isolation in cell culture is usually performed only in laboratories with the necessary infrastructure and technical expertise. For virus culture, it is important to keep blood samples cooled or frozen to preserve the viability of the virus during transport from the patient to the laboratory.

The isolation and identification of dengue viruses in cell cultures usually takes several days. Nucleic acid detection assays with excellent performance characteristics may identify dengue viral RNA within 24—48 hours. However, these tests require expensive equipment and reagents and, in order to avoid contamination, tests must observe quality control procedures and must be performed by experienced technicians.

NS1 antigen detection kits now becoming commercially available can be used in laboratories with limited equipment and yield results within a few hours. Rapid dengue antigen detection tests can be used in field settings and provide results in less than an hour.

Currently, these assays are not type-specific, are expensive and are under evaluation for diagnostic accuracy and cost-effectiveness in multiple settings. After day 5, dengue viruses and antigens disappear from the blood coincident with the appearance of specific antibodies. NS1 antigen may be detected in some patients for a few days after defervescence.

Dengue serologic tests are more available in dengue-endemic countries than are virological tests. Specimen transport is not a problem as immunoglobulins are stable at tropical room temperatures. For serology, the time of specimen collection is more flexible than that for virus isolation or RNA detection because an antibody response can be measured by comparing a sample collected during the acute stage of illness with samples collected weeks or months later.

Results of rapid tests may be available within less than one hour.Dengue (pronounced DENgee) viruses belong to the family Flaviviridae, genus Flavivirus. There are four serotypes: DENV-1, DENV-2, DENV-3, and DENV-4, which belong to a larger, heterogeneous group of viruses called arboviruses.

Dengue virus infection is a disease with symptoms ranging from simple flu-like illness to severe hemorrhagic symptoms, shock, encephalitis, or death, and is caused by any of four distinct Dengue virus species (DEN-1, -2, -3, or -4).

Clinical microbiology of the dengue virus

There are four serotypes of the virus that causes Dengue fever and infection by one subtype provides lifelong. Clinical Dengue. Infection with any of the four dengue serotypes can produce the full spectrum of illness and severity. The spectrum of illness can range from a mild, non-specific febrile syndrome to classic dengue fever (DF), to the severe forms of the disease, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).

Dengue virus (DENV) belongs to the family Flaviviridae, genus Flavivirus, and is transmitted to humans by Aedes mosquitoes, mainly Aedes aegypti.

Based on neutralization assay data, four serotypes (DENV-1, DENV-2, DENV-3, and DENV-4) can be distinguished. Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection.

Clinical microbiology of the dengue virus

This may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. Recovery generally takes two to seven days. INTRODUCTION The dengue virus causes dengue and dengue hemorrhagic fever. It is an arboivirus, within thia group it is from the family Flavivirade, which includes hepatitis c, West Nile, yellow fever and Japanese and St.

Louis encephalitis. All these viruses are spread by mosquitoes.

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