Dengue Fever

Overview

Dengue fever is caused by virus that is transmitted when a specific type of mosquito bites humans.

Four related types of dengue viruses (Denv-1, 2, 3 and 4) can cause dengue fever.

In majority of cases, the mosquito named Aedes aegypti  is responsible in the spread of the disease. The Aedes aegypti mosquito is mostly found in tropical areas including sub-continent, Pakistan, Africa and Latin America.

US - Centers for Disease Control and Prevention (CDC)
US – Centers for Disease Control and Prevention (CDC)

Dengue virus infection provides life-long immunity to the patient against re-infection from the same virus type. However, the patient is not protected from infection from the other types of dengue viruses.

Dengue infection is common in areas/ countries where there is high population of mosquitoes, especially, Aedes aegypti type mosquito. About half of the world’s population is at risk of getting dengue virus infection. It causes around 100 million infections every year, globally.  Recently one vaccine that provides limited protection against dengue fever has received approval in some countries. 

In majority of cases (about 85%) dengue virus infection causes mild flu like illness with fever that gets better itself in two weeks’ time with no later complications. In rare cases, patient develops a severe form known is dengue hemorrhagic fever (DHF), which is potentially life-threatening if not diagnosed and treated properly.

Signs and Symptoms

Symptoms of dengue fever develop in 4-10 days from the day virus enters the body.

Typically dengue infection causes following symptoms:

  • Sudden high fever reaching to 104-105 F
  • Severe headache – pain behind eyes
  • Bone, muscle pain or joint pain
  • Nausea and vomiting
  • Mild bleeding (from nose or gums)
  • Some patients also experience skin rash and increased sensitivity of skin

Above symptoms usually last for a week to 14 days. Complications may include high fever, seizure (febrile) and dehydration.

Dengue Hemorrhagic Fever (DHF)

DHF is a severe form of dengue infection.

Symptoms may include:

1. High fever for 2 – 7 days, similar to mild form of dengue infection

2. After fever reduces, patient develops severe vomiting and abdominal pain with breathing difficulty. The patient should be taken to the hospital as soon as experience these symptoms.

3. Bleeding – (sometimes internal) due to drop in platelet count

4. Excessive bleeding can cause shock and sudden drop in blood pressure that can lead to death.

5. Hospital admission is strongly recommended to treat the patient

6. According to WHO, if proper treatment is initiated in timely manner, fatality due to DHF is less than 1%

Causes and Risk Factors

Dengue fever is caused by one of the following four types of dengue viruses:

  • Denv 1
  • Denv 2
  • Denv 3
  • Denv 4

The virus is transmitted through the specific type of mosquito called Aedes aegypti.

This mosquito usually bites during early morning and evening time.

To prevent dengue fever, measures at community and personal level should be undertaken to avoid standing water in the streets, parks, backyards of houses in the neighborhoods and prevent mosquito bite by using appropriate insecticide, mosquito repellent products and nets.

Dengue virus cannot be transmitted from person to person directly.

However, dengue virus completes the infection cycle when the mosquito containing one of the four type of dengue virus bites a person and transfer the virus in the body. The person develops the dengue infection. The infection further spreads when the mosquito not containing the virus bites the dengue fever patient who have the virus in the blood. The virus is then transferred in the mosquito from the patient and then further transmitted by the same mosquito biting the healthy person to spread the infection.

The number of cases of dengue infection increases exponentially as more people are infected who further transfer the virus to the mosquito which bites more healthy persons.

It is therefore, important to keep the dengue fever patient in isolation so that further spread can be stopped.

Risk of dengue infection increases for people who live in the areas where dengue fever is common due to inappropriate sanitary conditions and poor cleanliness standards. Stagnant water in ponds, open sewage, water containers in farms and cities provide perfect opportunity for Aedes aegypti mosquito to breed.

Dengue fever is common in the following regions of the world:

• Indian Sub-continent including Pakistan

• South East Asia

• Africa

• Latin America

• Caribbean island

In addition to other reasons, increase travel has contributed in the spread of the disease across continents.

Diagnosis and Testing

Dengue fever most often diagnosed with typical signs and symptoms.

Dengue infection should be suspected in patient experiencing high fever, severe headache, pain behind the eyes and joint pain.

Travel history of the patient also helps in diagnosis; in case patient has recently visited the dengue endemic area/ country.

Complete blood count (CBC) test is also carried out to monitor the platelet count in blood.

Sometimes dengue fever can be misdiagnosed as symptoms are similar with malaria and typhoid fever.

Treatment

There are no specific treatments available for dengue fever. Dengue virus infection takes its own course and most patients start to feel better in one to two weeks.

Supportive symptomatic treatment for example regular fever controlling medication along with some pain medications (analgesics) are prescribed to relieve the pain.

Aspirin should not be used by the patient as it can further dilute the blood causing internal bleeding.

Patient should consume plenty of fluids (water and juices) to prevent dehydration. Patient should also stay home and take plenty of rest.

A recently developed dengue vaccine is approved and available in some countries

Most people recover completely in 2 weeks, some people feel fatigue and weakness up to 6 weeks.

Papaya plant leaves extracts and papaya fruit peel extract are used for the treatment of dengue fever.  No scientific evidence is available to support the use of papaya leaves, however it is used very commonly in Pakistan and India. Papaya leaves and fruit peels are boiled in water to make the juice. Patients are required to drink the juice several times a day.

Prevention

A recently developed dengue vaccine is approved and available in some countries

Dengue fever can be prevented by avoiding mosquito bite. Following measures can be taken to avoid mosquito bite:

  • Wear full sleeves shirts, pants, socks to protect mosquito bite especially during early morning and evening time
  • Use appropriate insecticides and mosquito repellent products
  • Use mosquito sleeping nets, wherever possible
  • Avoid standing water in the house, streets and neighbourhoods

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