Dengue fever is a viral infection caused by dengue virus. Dengue is spread by mosquitoes of the Aedes species, principally A. aegypti. The virus has five different types, infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications.
Mostly infection with dengue virus is asymptomatic or have mild flue like symptoms (80%) but few can have more severe illness (5%), and in a small proportion it is life-threatening. Children have a greater risk of severe complications.
Signs and symptoms
Fever: Fever is usually very high, lasts two to seven days. It may be associated with headache (typically located behind the eyes), generalized pain (Muscle and joint pains) and nausea and vomiting. The fever itself is biphasic in nature, breaking and then returning for one or two days.
Rashes: A rash occurs in 50–80% of those with symptoms. The rash of dengue fever in the acute stage of the infection blanches when pressed. The rash that commonly forms during the recovery from dengue fever with its classic islands of white in a sea of red. They may also be presence of red spots (petechiae) which do not disappear when skin is pressed. Some mild bleeding can occur from the mucous membranes of the mouth and nose.
Dengue shock syndrome (DSS) and Dengue hemorrhagic fever (DHF): In some people, the disease proceeds to a critical phase causing DSS and DHF, this occur after 3-5 days of fever. During this phase, fever has often come down and patients who remain ill, despite their temperature returning to normal, are more likely to develop shock. Shock generally occurs on day 3–4 of the illness. During this period there is leakage of plasma from the blood vessels causing fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood supply to vital organs, thrombocytopenia is a characteristic finding at this stage. This may cause organ dysfunction and severe bleeding, typically from the gastrointestinal tract. Death is usually due to severe haemorrhage or intractable shock with multiorgan failure.
Symptoms of DSS and DHS are similar to dengue fever but also have additional associated features like:
Severe and continuous pain in abdomen
Bleeding from the nose, mouth and gums, injection sites or other locations and skin bruising.
Frequent vomiting with or without blood
Black stools, like coal tar
Excessive thirst (dry mouth)
Pale, cold clammy skin
Restlessness, or sleepiness
During recovery phase there is resorption of the leaked fluid into the bloodstream. It may sometimes cause a state of fluid overload.at this stage there may be involvement of brain due to fluid overload causing reduced level of consciousness or seizures. Recovery stage may be accompanied with severe itching and a slow heart rate. A feeling of fatigue may last for weeks in adults.
Risk factors for the development of dengue shock
DHF/DSS is more likely to occur in infants and the elderly.
Dengue infection also appears to be more severe in females, in patients with chronic illness such as diabetes mellitus or asthma.
The serotype of the infecting virus may influence the severity of dengue; DEN-1 infection, followed by DEN-2 infection, has been reported to be associated with worse outcome.