Dengue: Symptoms and Prevention

Dengue is an infectious disease caused by the Dengue virus which is transmitted through the Aedes mosquito. This illness is encountered very commonly in various tropical regions with over 3.9 billion individuals at risk of acquiring the infection. The illness is seasonal, with epidemics occurring most frequently in the summer and monsoon or rainy months. Annually, nearly 400 million infections appear worldwide affecting all age groups. The disease is widely prevalent in Africa and the Indian subcontinent which are also the areas with the highest mortality from dengue.

The illness has varied severity of presentation ranging from asymptomatic cases that go unmissed to severe life-threatening bleeding and shock with death. The virus enters the bloodstream during a blood meal by the Aedes mosquito which itself gets the virus from an infected human. Upon entry, the virus activates the immune system to trigger a systemic immune response. This is responsible for the clinical features seen in the disease.

There are three stages if the illness as follows:

• Febrile stage: This is the initial stage marked with fever and headaches that lasts for 2-3 days
• Critical stage: In this stage, the fever resolves but there is a high risk for bleeding and shock due to a fall in platelet count and loss of fluid from the bloodstream. This is the most dangerous stage lasting 2-3 days, with a high risk of death is not managed adequately
• Recovery stage: This is the final stage of the disease with a resolution of symptoms, lasting 4-5 days. There is a return of platelets and blood cells to normal levels with recovery from low blood pressure.

Symptoms of Dengue

• Headaches
• Retro-orbital pain – this is aching pain felt behind the eyes
• Fever
• Skin rash: the rash typically appears as small red pin-point size lesions over the entire body
• Fatigue
• Generalized joint and muscle aches
• Dizziness from low blood pressure
• Bleeding from various sites including nose bleeds and bleeding gums during brushing
• Nausea, vomiting and abdominal pain may be present

Diagnosis of Dengue

Dengue is suspected clinically based on the classic symptoms in the setting of an outbreak and a history of travel or exposure to mosquitoes in an endemic area. The following tests are done to diagnose the illness

• Complete blood count: This usually reveals a falling platelet level and a decrease in white blood cell count
• Viral antigen testing: This is a blood test that detects viral antigens that trigger the immune system. This test for the NS1 antigen and is useful to confirm diagnosis within 5 days of symptom onset.
• Viral Nucleic acid testing: This is a PCR (Polymerase Chain Reaction) based test which tests for viral genetic material. This is also done within the first 5 days of the illness.
•  Antibody detection: The IgM and IgG antibodies produced against the dengue virus can be detected in the blood after 4-5 days from symptom onset.

Treatment of Dengue

There is no definitive treatment for curing dengue. The illness generally resolves on its own in about a week and requires effective supportive care.

• Adequate hydration: This is extremely important and forms the backbone of dengue management. Oral hydration in mild cases is often sufficient. Severe illness requires hospitalization with intravenous fluids.
• Shock management: severe cases may require vasopressors or medications to support blood pressure in an intensive care unit.

Prognosis of Dengue

The illness resolves in a week’s time and the individual can recover completely with no residual symptoms. The infection does not provide any immunity and in fact, a second attack of dengue is frequently more dangerous than the first one. It is important to protect oneself and their children from potential mosquito sources and bites.

Prevention of Dengue

• Protection from mosquito bites
• Avoiding areas with Aedes mosquito infestation
• Frequent spraying of indoor areas with repellents
• Wearing protective clothing to cover arms and legs
• Using mosquito repellent creams and bed nets
• Vaccine
• A new vaccine has been developed to protect from dengue called CYD-TDV which is being slowly made available across the world for use in those aged 9-45 years living in endemic regions. Several other vaccines are also under development.

References:

• Dengue and severe dengue [Internet]. World Health Organization. [cited 2018 Jun 25]

• Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, et al. The global distribution and burden of dengue. Nature. 2013 Apr 25;496(7446):504–7.