Dengue fever (also known as demam denggi in Malay) is a mosquito-borne viral infection, it usually presents as a self-limiting flu-like illness that affects infants, children, and adults. It may range from having no symptoms to severe symptoms, but it seldom causes death. Symptoms of dengue fever can be observed around 4-10 days (incubation period) after the bite of an infected Aedes mosquito, and the course follows 3 phases: febrile phase, critical phase, and recovery phase. Dengue infections are increasing at a rate higher than any other communicable disease, with over 400% increase over a 13 year (2000-2013) period. It is estimated that the annual dengue incidence globally is around 100 million symptomatic cases a year, and another 300 million asymptomatic cases with the greatest burden seen in Asia (75%).

The World Health Organization (WHO) has classified dengue into 2 major categories, which are dengue (with or without warning signs) and severe dengue. The sub-classification of warning signs is aimed to help medical professionals triage patients for hospital admission to ensure close observation on those with warning signs and to minimize the risk of developing severe dengue. People who have weakened immune systems and those with a second or subsequent are at a higher risk to develop severe dengue.

Dengue should be suspected if a person lives in or has traveled to a dengue-endemic area, and present with high fever (40°C/104°F) accompanied by at least 2 of the following symptoms during the febrile phase which lasts 2-7 days:

• Muscle, bone and joint pains
• Nausea
• Vomiting
• Severe headache
• Pain behind the eyes
• Swollen glands on the neck
• Rash

Dengue may present with or without warning signs, as warning signs may be an indication of progression to severe dengue. Some warning signs of dengue that may present in the late febrile phase around the time fever subsides include:

• Severe abdominal pain
• Persistent vomiting
• Rapid breathing
• Bleeding gums or nose bleeding
• Vomiting blood, blood in the stool or urine
• Unexplained bruising or blood spots under the skin
• Fatigue 
• Restlessness 

The critical phase of dengue begins when the fever subsides (below 38°C/100°F), which is usually around 3-7 days after the first sign of illness, and typically lasts 24-48 hours. Most patients improve clinically during this phase as the symptoms recede, but potentially fatal complications and the development of severe dengue may occur during this time hence close monitoring on the presence of any warning signs is crucial so that proper medical care can be provided. Severe dengue is the result of blood vessels become damaged and leaky, it is defined as dengue with any one of the following symptoms:

• Severe plasma leakage causing shock (when the body does not get enough blood flow) with cold or clammy skin, fluid accumulation with breathing difficulties
• Severe bleeding
• Severe organ impairment such as brain, liver, or heart

Severe dengue is a medical emergency, immediate medical attention or hospitalization is needed as it may result in death.

As the patient enters the recovery phase, his well-being improves as the hemodynamic status stabilizes. There may be an appearance of a rash that may cause your skin to peel and itch. It is important to practice preventive measures to avoid contracting a second or subsequent dengue infection as it increases the risks of severe dengue which may be life-threatening.