Dengue Fever (Aedes aegypti)

Dengue Fever

Dengue (DENG-gee) fever, also known as “Breakbone fever” is a viral fever caused by dengue virus transmitted by the bite of mosquito named Aedes aegypti (A.aegypti) in the tropical and subtropical areas. Open water sources are the main breeding places for mosquitos (A.aegypti), the main culprit of the dengue fever.

Dengue Virus

Aedes aegypti

Introduction & Background

Dengue fever, also known as “Breakbone fever” is a viral infection caused by dengue virus transmitted by the bite of mosquito named Aedes aegypti (A.aegypti) in the tropical and subtropical areas. Typical symptoms of the dengue fever include fever, headache, characteristic skin rash, generalized muscle and joint pain and pain behind the eyes. Dengue fever may be in mild form or may be in severe form depending upon the infection. The dengue fever is wide spread in its distribution throughout the world but it is especially notorious in tropical as well as in subtropical areas, such as

South east Asia
India
Pakistan
Sri Lanka
Mexico
China
Taiwan
Central and South America
Caribbean Islands
Africa
Pacific lands

Areas With Risk Of Dengue

Millions of cases of dengue fever occur worldwide every year. Dengue fever is most common in Asia (mainly Pakistan, Sri Lanka & India) and Pacific islands, but its incidence is increasing in America and Africa as well.

Distribution Of Dengue In The World

Dengue virus is a single stranded RNA virus that belongs to family Flavivridae, genus Flavivirus. Dengue has 5 serotypes and all the 5 serotypes can cause dengue fever. The genome of dengue virus consists of 11000 bases that code for structural as well as non-structural proteins. There are three basic structural proteins of dengue virus, capsid protein C, membrane protein M and envelope protein E. There are also 7 other main non-structural proteins such as NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5. Short coding regions are present on both 3’ and 5’ end of the genome.

What is Dengue Fever?

Dengue fever is a viral infection caused by dengue virus that is transmitted by the mosquito (A.aegypti). Dengue fever may be of mild form or may be severe form in terms of its severity depending upon the infection. The symptoms of the mild form of dengue fever include sudden onset of fever, headache, generalized body rash, joint and muscle pain throughout the body and pain behind the eyes. In small proportion of people the dengue fever may become life threatening and is known as dengue hemorrhagic fever. Dengue hemorrhagic fever is the sever form of the dengue fever. Dengue hemorrhagic fever has some additional signs and symptoms in addition to the typical symptoms of mild form of dengue fever, such as bleeding from the nose and mouth, significant fall in blood pressure which results in shock and this this condition is known as “dengue shock syndrome”.

Signs & Symptoms of Dengue Fever

Most of the people (80%) affected with dengue virus are asymptomatic i.e., they do not show the typical symptoms of dengue fever. The incubation period of the dengue fever ranges from 3-14 days but may be of short duration (4-7 days). Signs and symptoms of dengue fever may vary depending upon the severity of the disease. The dengue fever may be in mild form or may appear in severe form which is also known as “Dengue hemorrhagic fever”. Children may show signs and symptoms that may be quite similar to that of common cold and gastroenteritis i.e., vomiting and diarrhea etc. The characteristic signs and symptoms of dengue fever are fever which is of sudden onset form, rash, headache and joint pain etc.

Signs & Symptoms Of Dengue Fever

The signs and symptoms of dengue fever are following,

Headache
Malaise
Fever (106 °F or 41 °C)
Pain behind the eyes
Joint pain
Bleeding from nose or gums
Rash all over the body
Nausea
Vomiting

Dengue Symptoms

The fever present in dengue fever is characteristically biphasic in nature i.e., breaking and then again returning within one or two days.

Most of the people show mild form of dengue fever and recover within a week or sometimes more. In some cases, the symptoms persist and worsen and may become life-threatening for the patient. The platelet count is decreased which results in bleeding from nose and mouth due to leaky blood vessels. Other sign and symptoms in “Dengue hemorrhagic fever” form of dengue fever are following,

Bleeding from mouth and nose
Continuous vomiting
Abdominal pain
Petechial hemorrhages under the skin (Minor bleeding under the skin)
There may be complications of the heart, liver and lungs

When to See Your Doctor

Headache need not concern much if you are generally healthy and got signs and symptoms of joint pain, generalized body rash and pain behind the eyes, and then visit your doctor because it may be life threatening for you if you ignore these symptoms. International or national travel history is very important for the diagnosis.

How Dengue Fever is diagnosed?

The dengue fever is diagnosed clinically on the basis of clinical signs and symptoms as well as on the basis of physical examination. Early symptoms of dengue fever are difficult to differentiate from other viral infections. A probable diagnosis is made on the symptoms of fever, nausea, vomiting, rash, malaise, joint pain and low platelet count.

Diagnosis Of Dengue

Diagnosis is made in the persons who were being in the subtropical or tropical areas representing with fever within a week or so. Dengue fever is difficult to differentiate from Chikungunya. For this clinical investigations are done to differentiate between these two conditions. Similarly, laboratory investigations are required to exclude other similar conditions such as,

Malaria
Influenza
Typhoid fever
Measles
Viral hemorrhagic fever
Leptospirosis
Meningococcal disease

The initial detectable change on laboratory investigation is the fall in white blood cells (WBCs) count. Elevated levels of aminotransferases (AST & ALT) are also associated with fall in platelet count and plasma leakage. While plasma leakage in return is associated with pleural effusion or ascites.

The diagnosis of dengue fever is confirmed by laboratory investigations. Following laboratory investigations are performed to diagnose dengue fever,

Cell cultures
PCR for nucleic acid detection
Specific antigens detection
Specific antibody detection

For first 7 days, specific antigens and PCR are most accurate tests for the diagnosis of the acute dengue fever. Laboratory investigations for dengue specific antibodies are also helpful. I_gM and I_gG are also helpful in the diagnosis. A rise in titer of I_gM is associated with primary infection with dengue virus.

Risk Factors

The factors which can predispose a person to dengue fever are following,

Travelling to subtropical or tropical areas of the world
Previous infection with dengue virus
Compromised immune system
Female sex
High body mass index (BMI)
Diabetes
Asthma

Complications

In the severe form of dengue fever, the dengue virus can affect heart, liver and lungs. The blood pressure may fall to a dangerous level, the condition known as dengue shock syndrome. There is a risk of inflammation of brain by dengue virus. Other rare complications associated with dengue fever are following,

Guillain-Barŕe syndrome
Transverse myelitis
Acute liver failure
Infection of the heart

Treatment

There is no specific medication for the treatment of dengue fever except maintaining fluid level of the body. Over the counter (OTC) pain killers are advised to relieve the joint pain, headache and pain behind the eyes but those painkillers are contraindicated in dengue fever which increase the bleeding tendency such as aspirin, naproxen and ibuprofen. Paracetamol (acetaminophen) is used for the treatment of fever.

Treatment Of Dengue

The patients with severe dengue fever are admitted to intensive care unit (ICU) and then following interventions are required,

Blood pressure monitoring and maintenance
Supportive care
Maintaining body fluid level

Preventions

Do not come outside wearing half sleeves shirt.
Ensure that public health bodies and communities are strengthened.
There should be adequate collaboration between the health and other sectors (public and private).
Maximize use of health resources to control disease with an integrated approach.
Decisions should be made to ensure that all interventions are targeted appropriately.
Provide an adequate response to the local situation.
Open water sources are the breeding places of the mosquitoes. Eliminate the breeding places of mosquitoes.
Spraying with organophosphorus insecticides.
The main method of controlling A. aegypti, main cause of dengue fever, is by eliminating its natural breeding places. This is mainly done by eliminating open sources of water.
Always wear long sleeves shirts and long pants in the areas of mosquitoes.

Lifestyle modifications & Home Remedies

The juice of papaya leaf has been seen to inhibit the destruction of platelets.

Papaya Fruit

Papaya Leaf

The main method of controlling A. aegypti, main cause of dengue fever, is by eliminating its natural breeding places of mosquitos. This is mainly done by eliminating open sources of water.
Always wear long sleeves shirts and long pants in the areas of mosquitos.
Stay in well screened rooms in order to avoid mosquitos.
Use mosquito repellents.