By: dr. A. A. Ngr. Andika Damarnegara,S.Ked
The Dengue Virus (DENV) causes a wide range of diseases in humans, from a self-limited Dengue Fever (DF) to a life-threatening syndrome called Dengue Hemorrhagic Fever (DHF) or Dengue Shock Syndrome (DSS). It is a mosquito-borne single positive-stranded RNA virus of the family Flaviviridae. It was first isolated in 1943, and have been identified to four serotypes (DENV1-4), although the fifth type have been founded in a report in 2013. The incidence of dengue has grown dramatically around the world in recent decades. The actual numbers of dengue cases are underreported and many cases are misclassified. One recent estimate indicates 390 million dengue infections per year (95% credible interval 284–528 million), of which 96 million (67–136 million) manifest clinically (with any severity of disease). The disease is now endemic in more than 100 countries in the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. The America, South-East Asia and Western Pacific regions are the most seriously affected.
The Aedes Aegypti mosquito is the primary vector for the dengue virus. The virus is transmitted to humans through the bites of infected female mosquitoes. These mosquitos usually live between the latitudes of 35o North and 35o South below an elevation of 1000 meters. And they typically bite during the early morning and in the evening, but may bite and spread the virus at any time of day. After virus incubation for 4-10 days in the mosquito, the infected mosquitoes are capable to transmit the virus for the rest of its life. In human, the infected person can be symptomatic or asymptomatic, and they will be the main carriers and multiplier of the virus, and will become a source of the virus for uninfected mosquito.
People infected with dengue virus are 80% asymptomatic or have only mild symptoms such as an uncomplicated fever. Others have more severe illness and in a small proportion it is life-threatening. And the symptoms appear after an incubation period (time between exposure and onset of symptoms) ranges from 3 to 14 days, but most often it is 4 to 7 days.
In children the symptoms are often similar to those of the common cold and gastroenteritis (vomiting and diarrhea). The characteristic symptoms of dengue are sudden-onset fever, headache, pain behind the eyes, severe joint and muscle pain, fatigue, nausea, vomiting, skin rash (which appears two to five days after the onset of fever), and mild bleeding. And the course of infection is divide into three phases: febrile phase, critical phase, and recovery phase.
The febrile phase involves high fever, potentially over 40oC and associated with generalized pain, headache, nausea and vomiting and rash may occur in 50-80% of the infected people, this phase usually last two to seven days. The fever itself is classically biphasic or saddleback in nature, breaking and then returning for one or two days.
In some people, the disease proceeds to the critical phase when the fever resolves. There is leakage of plasma from the blood vessels, and typically lasting one to two days. This may result depletion of fluid from circulation and decreased blood supply to vital organs. And may also be organ dysfunction and severe bleeding. Shock (DSS) and hemorrhage (DHF) occur in less than 5% of all cases of dengue. And people with secondary infection are at an increased risk and commonly in children and young adults.
The recovery phase occurs with resorption of the leaked fluid into the bloodstream and last two to three days. The improvement is often striking and can be accompanied with severe itching and slow heart rate. And during this stage, a fluid overload state may occur. And if it affects the brain may cause a reduced level of consciousness or seizures. And feeling of fatigue may last for weeks in adults.
The first dengue epidemics occurred almost simultaneously in Asia, Africa, and North America in the 1780s, after the identification and naming of the disease in 1779. A pandemic began in Southeast Asia in the 1950s, and in 1975 DHF become a leading cause of death among children in the region, and the first case of DHF was reported in Manila around 1953 through 1954. And by the late 1990s, dengue was the most important mosquito-borne disease affecting humans after malaria, with around 40 million cases of dengue fever and several hundred thousand cases of DHF each year. Significant outbreaks of DF tend to occur every five or six months. The cyclical rise and fall in numbers of dengue cases is the result of seasonal cycles interacting with a short-lived cross-immunity for all four strains in people who have had dengue.
The DHF is one of the leading causes of hospitalization and death in children in many southeast Asian countries, and Indonesia reporting the majority of DHF cases. In Indonesia, young adults in Jakarta and provincial areas make up a larger percentage of infected patients. In Singapore in the year 2004, there were seven deaths from DSS, and in 2013 there was a major outbreak with a total of 21,324 cases by the end of the year.
In the 2015 dengue outbreak in Taiwan, a significant rise in the number of dengue fever cases was reported in Tainan City, Kaohsiung City, and Pingtung City. As of the end of 2015, official data showed that more than 40,000 people and more than 200 people death, mostly in these three cities, were infected in 2015. This epidemic began in the summer of 2015, with the first reported occurrence in the North District, Tainan. There were several documented cases in other cities and counties but none resulted in death or were of such large scale.
The diagnosis of DENV infection is usually made clinically. The classic picture is high fever with no localizing source of infection, a petechial rash with low thrombocyte and relative low white blood cell. Care has to be taken as diagnosis of DHF can mask end stage liver disease and the other disease. If someone have persistent fever more than that 2 days then they should go for complete blood check, and if the thrombocyte and white blood cell are below than their range, they should go for Dengue Antigen test.
In DENV infection there are three essential laboratory tests may help in the evaluation of the real clinical conditions of the patient and its early supportive management:
And for a diagnosis of DHF grade I, each of four criteria must be met. Fever that’s not specific and constitutional symptoms and the only haemorrhagic proof being positive tourniquet test. Grade II is similar to grade I, but has specific haemorrhagic manifestations, and the sign of circulatory failure or hypertension are graded under Grade III, and profound shock with pulse and blood pressure that is undetectable is under Grade IV.
Because the DF is caused by a virus, the only treatment is to treat the symptoms. For typical dengue, the treatment is purely concerned with relief of the symptoms, rest and fluid intake for adequate hydration. The treatment with aspirin, ibuprofen and non-steroidal anti-inflammatory drugs should be avoided as these drugs may worsen the bleeding tendency associated with some of these infections. Patients may receive paracetamol preparations to deal with these symptoms if dengue is suspected. And any medicines that decrease platelets should be avoided.
Prevention depends on control of and protection from the bites of the mosquito that transmits the DENV and eradication of mosquitoes (anti-vectorial prevention). For the protection from the mosquitos bite use insect repellent on skin while indoors or out, mosquito traps or mosquito nets. There are common insect repellants include:
Wear also long sleeves and pants for additional protection. Also make sure windows and door screens are secure and without holes and if available use air-conditioning. And sleep under a mosquito bed net if you are overseas or outside and are not able to protect yourself from mosquito bites.
The elimination of the mosquitos is an important thing for prevention of DENV infection. The best way to reduce the mosquitos is to eliminate the places where they lay her eggs, like artificial containers that hold water in and around the home. Periodic draining or removal of artificial containers is the most effective way of reducing the breeding grounds for mosquitos.
For majority of adult peoples infected with DENV, the prognosis is excellent with complete recovery, although they feel very ill during the first one or two weeks of the acute illness and weak for about one month. And people who have been infected by one DENV type are still able to be infected by the remaining three types. And the second infection increases the possibility that complications will develop, so peoples with second-time DF have a less optimal prognosis.
And the peoples who develop DHF or DSS have a range of outcomes from good to poor prognosis, depending on their underlying medical problems and how quickly supportive measures are given. For example, DHF and DSS have about 50% fatality rate if untreated but only about a 3% rate if treated with supportive measures. Overall, the fatality rate is about 1% for all dengue fever infections. While this rate may seem low, worldwide it means that about 500,000 to 1 million people die each year from dengue fever. This is a concern since the worldwide case numbers and outbreaks are increasing