Overview of Dengue
Dengue and dengue hemorrhagic fever (DHF) are acute febrile diseases, caused by a family of viruses that are transmitted by mosquitoes.
It is transmitted by the bite of an Aedes aegypti (rarely Aedes albopictus) mosquito that has been infected with any one of the four dengue viruses. This disease is predominant in the tropical and sub-tropical areas of the world. In fact the geographical spread of the disease is similar to that of malaria. This disease is caused by one of four closely related virus serotypes of the genus Flavivirus, family Flaviviridae. Each of these serotypes is sufficiently different. As a result there is no cross-protection and therefore epidemics are caused by multiple serotypes (hyperendemicity). The patient becomes immune for a lifetime to the serotype that caused his dengue attack.
Dengue is also known as "breakbone" or "dandy fever." The name breakbone fever was given because of the contortions caused due to the intense joint and muscle pain. The name dandy fever was given because of the postures and gait of West Indian slaves who contracted dengue.
Dengue hemorrhagic fever is a more severe form of the viral illness and can be life-threatening or even fatal.
Causes of Dengue
As said before dengue and dengue hemorrhagic fever (DHF) is caused by dengue virus which belongs to genus Flavivirus family Flaviviridae. This virus is transmitted by Aedes aegypti mosquito that has previously bitten an infected person. This species of mosquito flourishes during rainy seasons. However, they can breed all round the year in water-filled flower pots, plastic bags, and cans. One mosquito bite is strong enough to inflict the disease.
However, the virus is not contagious and does not spread from person to person. It requires the mosquito as a medium and a person-to-mosquito-to-another-person pathway.
Symptoms of Dengue
The incubation period of dengue fever is usually 5 – 6 days. However, this period at times may vary between 3 to 10 days. Dengue fever affects one and all, starting from infants to young children and adults. But it is seldom fatal in nature.
The symptoms manifested by dengue vary according to the age of the patient. Infants and young children usually have a non-specific febrile illness which is characterised by the appearance of rash.
On the other hand, the symptoms manifested by older children and adults are:
- Abrupt onset of high fever (up to 105 degrees Fahrenheit)
- Severe headache
- Severe muscle and joint pain (break bone fever)
- Rash and other haemorrhagic manifestation
However, DHF is a potentially deadly complication and the symptoms manifested are:
- High fever
- Vomiting and abdominal pain
- Haemorrhagic diathesis, commonly demonstrated by scattered fine petechiae on the extremities, face, trunk, and in the axillae
- Bleeding nose, gums, and gastrointestinal tract
- Haematuria (though a rare symptom)
- Enlargement of the liver
The fatality in DHF is caused by leakage of plasma in the pleural and abdominal cavities leading to hypovolaemic shock. A fall in platelet count and a rise in haematocrit level is a unique characteristic of DHF. Hence for diagnosis and case management purpose the haematocrit value and platelet count is continuously monitored.
The alarming signs in Dengue are:
- Bleeding nose and gums, hemetemesis
- Refusal to food or drink
- Difficulty in breathing
- Reduced urination
- Minute spots on the skin signifying bleeding within the skin
- Abnormal behaviour
Diagnosis of Dengue
The following types of test are used in the diagnosis of Dengue:
Isolation of virus in serum.
This is done through inoculation in tissue culture. The identification is confirmed using fluorescent antibody test. Viral genomic sequences are usually detected in CSF, serum or autopsy tissue sample by using PCR (Polymerase Chain Reaction).
Serological tests are used for confirming DF/DHF. These tests detect the presence of IgM antibodies. The IgM antibodies appear at the end of the first week of onset of symptoms. They remain detectable for about 1 – 3 months after the acute episode. The presence of IgM antibodies, sero-conversion of IgM antibody or a fourfold difference in titre of IgG antibody in paired sera taken at an interval of ten days confirms DF/DHF. However, high presence of IgG antibodies early in the course of illness indicates previous infection. The tests conducted are enzyme-linked immunosorbent assay (ELISA) antibody capture, monoclonal antibody, or hemagglutination.
- Electrolyte imbalances
- Elevated BUN
This test confirms the presence of occult blood in stool.
Complete blood count
- Hemoconcentration (hematocrit increased by 20%)
- Thrombocytopenia (platelet count <100 x 109/L)
Liver function tests
- Elevated transaminases
- Pleural effusion
Head CT scan without contrast
For altered level of consciousness
- Intracranial bleeding
- Cerebral edema
Treatment for dengue
Dengue is caused by a virus. There is no specific treatment or antibiotic for it. The treatment provided to a patient during dengue infection is mainly supportive in nature which is purely concerned with the relief of the symptoms (symptomatic). The patient is advised to take complete rest and increase the intake of fluids in order to prevent dehydration and significant hemo-concentration. However, if the patient is unable to maintain oral intake, supplementation with intravenous fluids may be necessary. One should avoid Aspirin and non-steroidal anti-inflammatory drugs. The patient may be given Acetaminophen (Tylenol) and codeine to provide relief from severe headache and joint and muscle pain (myalgia).
In case if the platelet level drops significantly, a platelet transfusion becomes necessary.
Patients who develop signs of dengue hemorrhagic fever require closer observation. Patients who develop signs of dehydration, such as tachycardia, prolonged capillary refill time, cool or mottled skin, diminished pulse amplitude, altered mental status, decreased urine output, rise in hematocrit levels, narrowed pulse pressure, or hypotension, should be admitted in a hospital immediately for intravenous fluid administration as well as medical observation.
Patients who are resuscitated from shock recover rapidly. However, patients with dengue hemorrhagic fever or dengue shock syndrome (DSS) may be discharged from the hospital when they meet the following criteria:
- Afebrile for 24 hours without antipyretics
- Adequate urine output
- Platelet count greater than 50,000 cells/μL
- Stable hematocrit level
- At least 48 hours since recovery from shock
- Absence of respiratory distress
- Good appetite, clinically improved condition
Typical dengue usually does not result in death. The acute phase of the illness with fever, myalgias and the rest of the symptoms lasts for about one to two weeks. Convalescence is accompanied by a feeling of weakness (asthenia). However, full recovery often takes several weeks.
Treated DHF/DSS is associated with a 3% mortality rate.
Untreated DHF/DSS is associated with a 50% mortality rate.
The best precaution for Dengue is the prevention of mosquito bites.
Some important tips:
- Use insect repellent containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535 on exposed skin.
- Wear long sleeves and pants.
- Treat the clothes with permethrin or other repellents.
- Use secure screens on windows and doors to keep mosquitoes out.
- Get rid of mosquito sources in and around the house by emptying standing water from flower pots, buckets and barrels. Also, change the water in pet dishes and replace the water in bird baths once every week. In order to drain out water, drill holes in tire swings. Moreover, keep children's wading pools empty while not at use
- Since the infection of dengue essentially requires a mosquito, the transmission of the virus to mosquitoes must be interrupted in order to prevent the illness. To achieve this, infected patients should limit his exposure to mosquito bites and remain confined under mosquito netting until the second bout of fever is over. Thereafter, the infection is no longer contagious.
Currently, no vaccine is available for the prevention of dengue infection. However, immunogenic, safe tetravalent vaccines have been developed and are undergoing clinical trials. Since the major risk factor for dengue hemorrhagic fever and dengue shock syndrome is the immunity to a single dengue strain, the developed vaccine must provide high levels of immunity to all the four strains of dengue in order to be clinically useful.
Written by: healthplus24.com team
Date last updated: August 13, 2015