Dengue

August 23, 2019Diabliss1

“Recognizing its importance, Aedes aegypti should be studied as a long-term national, regional, and world problem rather than as a temporary local threat to the communities suffering at any given moment from yellow fever, dengue or other aegypti-borne disease.”

– Fred Lowe Soper, Building the Health Bridge: Selections from the Works of Fred L. Soper

Dengue fever

Dengue fever, also known as breakbone fever, is a vector-borne disease which meant that the virus takes the help of another organism to cause dengue in humans. Dengue fever is caused by Flavivirus virus belonging to the Flaviviridae family. These viruses cause infection usually through arthropod (insect) vectors. Dengue virus is transmitted through female infected Aedes aegypti mosquitoes.

The vector

This disease is one of the most common insect-borne viral illnesses in humans. The mosquitoes causing the disease are widely distributed in subtropical and tropical areas due to which the increased incidence of dengue is seen in those areas.

Where is the infection found?

The World Health Organization (WHO) regards dengue as one of the major global public health challenges in and around the equatorial regions of Africa, the Americas, South- East Asia, and the Western Pacific. The incidence is about 30 times greater than that of the epidemiological status before 1960. Researches attribute the rapid growth due to the:

• Unplanned population growth rate
• Inefficient mosquito control
• Global warming
• Frequent air travel
• Impromptu urbanization
• Inadequacy of health care facilities

Currently, about 50 million to 528 million people are infected annually with a mortality rate of about 5–20%. Dengue holds endemic status in more than 110 countries and had become a global problem since World War II.

A brief Indian historical perspective

• Though the 1st reported dengue epidemiology in the Indian subcontinent was in 1780 in Madras (now Chennai) it was after nearly two centuries later i.e. in 1963 that the 1st outbreak was seen in Calcutta (now Kolkata).
• Before 2001, this disease was endemic only to a few southern (Maharashtra, Karnataka, Tamil Nadu, and Pondicherry) and northern states (Delhi, Rajasthan, Haryana, Punjab, and Chandigarh)
• In the recent decades, dengue had recently spread to many states, as well as the union territories.
• Earlier dengue which had been restricted only to urban areas but has now spread to rural regions too.

Dengue classification

Dengue can be classified based on the disease’s severity levels. The disease can be manifested asymptomatic or may lead to undifferentiated fever, dengue fever (DF), or dengue haemorrhagic fever (DHF) with plasma leakage resulting in hypovolemic shock (Dengue Shock Syndrome, DSS). Symptoms of dengue typically begin about 3-15 days after being bitten by an infected mosquito.

Dengue Fever

1. The individual may get high fever with sudden onset at times with severe headache, pain located at the back of eyes, pain at bone and joints, nausea, vomiting and rash. Leucopaenia (reduced white blood cells) and thrombocytopenia (reduced blood platelets) are usually seen.

Dengue hemorrhagic fever

The four common signs with which DHF is typically characterized by are:

1. High fever
2. Circulatory failure
3. Hepatomagaly (increased liver)
4. Thrombocytopenia

• A sudden and unexplained rise in temperature with facial flush and other nonspecific constitutional symptoms such as the anorexia, vomiting, headache, and muscle or bone and joint pain are commonly seen in children affected with DHF.
• A steady-state of increased temperature (<102.2 °F) though observed for about 2-7 days; occasionally as high as 104-105.8 °F temperatures are reported resulting in febrile convulsions in infants.

Dengue shock syndrome

• The patients who went to shock suddenly deteriorate after 2-7 days of fever.
• The common signs of circulatory failure are:
  • Cool blotchy and congested skin
  • Bluish color around the mouth
  • Acute abdominal pain before onset of shock

DSS characterizations:

1. Faint accelerated (pulse pressure <20mmHg)
2. Reduced blood pressure (100/90 mmHg)
3. Cold clammy skin
4. Restlessness

Diagnosis of Dengue

The classic picture of high fever, skin rash with thrombocytopenia and leucopenia are the common symptoms. A complete blood picture can be performed if fever exceeded more than 2days then and a Dengue Antigen test must be done if the platelet count and WBC count are low.

Even when the definitive diagnosis isn’t yet established the following three laboratory tests help in the assessment of the real clinical conditions of the patient thereby suggesting in the supportive management:

• Total White Blood Cells Count: Reduced blood cells  could  depict dengue,  (2000-4000/μL).
• Platelet count: Thrombocytopenia (less than 100.000 per mm³) is a classic marker.
• Hemoconcentration: (increased red blood cells concentration but decreased plasma volume).