What is Dengue Virus (DENV) and How to Detect It?
Affecting around 100-400 million people each year, dengue fever remains among the major causes of serious illness and death in many parts of the world. The global incidence of dengue has grown rapidly throughout the recent decades. Since the majority of dengue infections are asymptomatic, mild, or self-managed, dengue infections are largely underreported. Moreover, a significant portion of dengue cases are misdiagnosed as other febrile diseases such as malaria, influenza, and leptospirosis. With the recent emergence and circulation of SARS-CoV-2 in dengue virus (DENV)-endemic areas further complicate the diagnosis of dengue. Altogether, the actual incidence of dengue is likely to be much higher than reported.
Thus, the ability to promptly detect and differentiate dengue infections proves to be of prime importance to clinicians, especially in tropical and subtropical countries. Thankfully, significant progress is being made in the detection and differentiation of dengue infections. With the advancements in diagnostics, various forms of diagnostic tests with different methods, characteristics, and purposes have become available in the diagnosis of dengue. Moreover, notable developments in rapid detection technologies offer promising benefits for case management, surveillance, and public health. Read along to learn more about dengue virus (DENV) and the current methods available for its diagnosis.
What is dengue virus (DENV)?
Dengue virus (DENV) is the virus responsible for causing dengue fever. Dengue virus (DENV) is a mosquito-borne, single positive-stranded RNA virus of the Flavivirus genus in the family Flaviviridae. It shares the Flavivirus genus with various viruses such as the West Nile virus, yellow fever virus, and Zika virus. So far, four serotypes of dengue viruses have been identified, which are DENV-1, DENV-2, DENV-3, and DENV-4. While it has not been confirmed yet, a fifth serotype of dengue virus (DENV) has recently been reported. Due to the lack of cross-protection between these serotypes, while infection with one serotype allows for life-long immunity against future infections with the same serotype, it provides little immune protection against infection with the other serotypes.
How do dengue viruses (DENV) transmit?
Dengue viruses transmit through the bite of infected female mosquitoes of the Aedes species, primarily Aedes aegypti. Although their life cycle originally involved transmission between Aedes mosquitoes and non-human primates, dengue viruses are known to almost exclusively transmit between humans and Aedes mosquitoes in the present day. Apart from rare cases of reported transmission via blood products, organ donation and transfusions, human-to-human transmission of dengue viruses (DENV) has not been recorded.
How common is dengue fever?
According to the World Health Organization the incidence of dengue has increased 30-fold throughout the last 50 years. Today, the agency estimates that dengue affects up to 100-400 million people each year in more than 100 endemic countries across Africa, the Americas, South-East Asia, the Western Pacific and the eastern Mediterranean.
What are the common symptoms of dengue fever?
Approximately 80% of dengue infections are asymptomatic or mild. However, dengue viruses may also occasionally manifest as severe flu-like illness, which may develop into a potentially fatal complication called severe dengue. Symptoms of dengue typically appear following an incubation period of 4 to 10 days and last for 2 to 7 days. Common symptoms of dengue include high fever which may be combined with severe headache, nausea, vomiting, swollen glands, myalgia, joint pain, pain behind the eyes, or a characteristic skin rash.
Critical phase for the risk of severe dengue typically starts 3 to 7 days following illness onset. Severe dengue is a life-threatening complication which may result in blood plasma leakage, fluid accumulation, respiratory distress, severe bleeding, and organ impairment. During the critical phase, signs that might be indicative of severe dengue include severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums/nose, fatigue, liver enlargement, and blood in vomit/stool.
Which diagnostic methods are available for the detection of infections with dengue virus (DENV)?
There are several diagnostic methods available for the detection of infections with dengue virus (DENV). Depending on the time of patient presentation and the level of access to laboratory technology, the application of different diagnostic methods may be more or less suitable.
Nucleic acid amplification tests (NAAT), including reverse transcriptase–polymerase chain reaction (RT–PCR) tests, detects the viral RNA of the dengue virus (DENV) with the highest level of specificity at the early onset of infection. However, in areas where access to laboratory equipment and trained personnel may be insufficient, these methods may not be easily available.
On the other hand, antigen-detection tests, including NS1-based assays such as our Dengue NS1 Ag Rapid Test Kit, detects antigens specific to dengue virus (DENV). Compared to Nucleic acid amplification tests (NAAT), antigen-based tests demonstrate a lower level of sensitivity especially during the acute phase of secondary dengue infections. However, they offer a simplified method which does not require laboratory equipment or specially trained personnel.
Serological tests, such as our Dengue IgG/IgM/NS1 Combo Rapid Test Kit which also covers NS1 antigens, detect the presence of anti-dengue IgG and/or IgM antibodies in order to check for the presence of a recent of past dengue infection. Detectable during the period between 7 days to 3 months following infection, the presence of IgM antibodies indicates a recent infection. IgG antibodies, on the other hand, require more time to develop, and indicates a past infection. As IgG antibodies can remain in the body for years, their presence may be associated with long-term immunity against a serotype of dengue virus (DENV).
How can you prevent infections with dengue virus (DENV)?
The only vaccine currently available against dengue virus (DENV) is Dengvaxia (CYD-TDV) by Sanofi-Pasteur. Combining a weakened version of the yellow fever virus, and each of the four dengue serotypes, Dengvaxia (CYD-TDV) has become commercially available in 2016 and has been approved for use in Mexico, Brazil, El Salvador, Costa Rica, Singapore, Paraguay, United States, along with many countries in Europe. Due to evidence suggesting that the vaccine may worsen subsequent infections with dengue viruses (DENV), the vaccine has not been found suitable for mass immunization. However, when used in endemic areas and/or in individuals with prior dengue infections, Dengvaxia (CYD-TDV) has demonstrated 66% efficacy. Moreover, it was found to prevent more than 80-90% of severe cases caused by dengue.
Further prevention can be achieved through the elimination of mosquito breeding sites, proper disposal of waste or stagnant water, and sufficient access to mosquito nets, repellents, and other protective items. The primary personal precaution that can help prevent infections with the dengue virus (DENV) is to avoid mosquito bites as much as possible and to refrain from activities near mosquito-breeding sites.
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