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Clinical course

The course of infection is divided into three phases: febrile, critical, and recovery.

The febrile phase involves high fever (40 °C/104 °F), and is associated with generalized pain and a headache; this usually lasts two to seven days. There may also be nausea, vomiting, a rash, and pains in the muscle and joints.

Most people recover within a week or so. In about 5% of cases, symptoms worsen and can become life-threatening. This is called severe dengue (formerly called dengue hemorrhagic fever or dengue shock syndrome). Severe dengue can lead to shock, internal bleeding, organ failure and even death. Warning signs include severe stomach pain, vomiting, difficulty breathing, and blood in the nose, gums, vomit or stools.

During this period, there is leakage of plasma from the blood vessels, together with a reduction in platelets. This may result in fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood supply to vital organs.

The recovery phase usually lasts two to three days. The improvement is often striking, and can be accompanied with severe itching and a slow heart rate.