Dengue Fever: Symptoms, Causes, and Treatments

What is Dengue Fever?

Dengue Fever (also known as break-bone fever) is a viral infection caused by the Dengue virus, which is transmitted to humans through the bite of infected female mosquitoes (Aedes aegypti). These dengue fever-carrying mosquitoes generally bite during the daytime (both inside and outside the house). It has been observed that these mosquitoes are most active during dawn and twilight. Dengue fever symptoms show up only six to ten days after being bitten by an infected mosquito. 
 

About Dengue Fever and Its Life Cycle

The dengue fever virus has a specific lifecycle that involves transmission between humans and Aedes mosquitoes, particularly the Aedes aegypti species. Here is a step-by-step description of this lifecycle: 

1. Aedes Mosquito Life Stages

The Aedes aegypti mosquito goes through four main life stages - Egg, Larva, Pupa, and Adult. It takes about 8 to 10 days for the mosquito to develop from an egg to an adult, increasing the chances of spreading dengue fever.

2. Egg Stage

Adult female mosquitoes lay their eggs just above the waterline on the wet walls of water-filled containers. Typically, a female mosquito lays around a hundred eggs at a time. These eggs are very resilient and can survive drying out for up to eight months, and they stick to container walls like glue. This stage is critical in the spread of dengue fever, as even a small amount of standing water can be a breeding ground.

 3. Larva Stage

The eggs then hatch into larvae once the water level rises enough to cover them, which can happen due to rain or human actions. The larvae live in the water and feed on aquatic bacteria and get transformed into a pupa.

4. Pupa Stage

The pupae continue to grow until the adult mosquito’s body is fully formed and capable of spreading dengue fever. 

5. Adult Stage

Adult Male mosquitoes feed on nectar from flowers whereas female mosquitoes feed on human and animal blood to produce eggs which ultimately results in dengue fever. 
 

Signs and Symptoms of Dengue Fever

Dengue fever is a mosquito-borne illness caused by the dengue virus. The symptoms usually appear 4 to 10 days after being bitten by an infected mosquito and can range from mild to severe. Here are the common signs and symptoms:

Mild Dengue Fever Signs and Symptoms

• High Fever - Sudden high fever (up to 104°F or 40°C) lasting for 2 to 7 days.
• Severe Headache - Intense pain in the head, often around the forehead. 
• Pain Behind the Eyes - Pain in the eye sockets, especially when moving the eyes.
• Muscle and Joint Pain - Severe pain in the muscles and joints, sometimes referred to as "breakbone fever", a nickname often used when describing dengue fever. 
• Nausea and Vomiting - Feeling nauseous and sometimes vomiting.
• Rash - A rash that appears a few days after the fever starts. It may start on the face and spread to the body and limbs.
• Fatigue - Extreme tiredness and weakness.
• Bleeding - Minor bleeding such as nosebleeds, gum bleeding, or easy bruising.

Severe Dengue Fever Signs and Symptoms 

In some cases, dengue fever can progress to severe dengue, which can be life-threatening and requires immediate medical attention. Signs and symptoms of severe dengue are:

• Severe Abdominal Pain - Intense pain in the stomach area.
• Persistent Vomiting - Frequent and severe vomiting.
• Bleeding - Severe bleeding from the nose, gums, or under the skin, which can lead to large bruises.
• Blood in Vomit or Stools - Vomiting blood or passing bloody stools.
• Breathing - Difficulty in breathing or rapid, shallow breaths.
• Fatigue and Restlessness - Severe lethargy, irritability, or restlessness.
• Organ Failure - In severe cases, there may be damage to the liver, heart, or other organs.
• Plasma Leakage - Fluid leaking from blood vessels can cause swelling and fluid accumulation in the abdomen or lungs.
• Shock - Severe drop in blood pressure, leading to shock, which can be fatal if not treated promptly.

Different Modes of Transmission and Causes of Dengue Fever

Transmission Through Mosquito Bites

• Primary Vector - The dengue fever virus is primarily transmitted to humans through bites from infected female Aedes aegypti mosquitoes. Other Aedes species, like Aedes albopictus (tiger mosquito), can also transmit the virus, with recent increases in Europe.
• Virus Replication - After biting an infected person, the virus replicates in the mosquito’s midgut and spreads to the salivary glands.
• Extrinsic Incubation Period (EIP) - This is the time from when the mosquito ingests the virus to undergo development to be able to infect humans. It is usually 8-12 days at temperatures between 25-28°C and factors like temperature fluctuations and virus genotype can influence this period.
• Lifelong Infectiousness - Once infected, the mosquito can transmit the virus for the rest of its life.

Human-to-Mosquito Transmission

• Viremic Humans - Mosquitoes become infected when they bite people with the dengue virus in their blood, whether the person is symptomatic, pre-symptomatic, or asymptomatic.
• Transmission Window - Mosquitoes can become infected up to 2 days before a person shows symptoms and up to 2 days after their fever goes down. 

Maternal Transmission

• Vertical Transmission - Though rare, dengue can be transmitted from a pregnant mother to her baby. The risk depends on the timing of the mother's infection during pregnancy.
• Impact on Babies - Infected mothers may have babies who experience pre-term birth, low birth weight, and fetal distress.

Other Transmission Modes

Rare cases of transmission via blood products, organ donation, and transfusions have been recorded. 

Who do Dengue Fever Viruses affect the most?

Dengue fever has a Global Impact as more than half of the world's population is at risk of dengue due to living in or traveling to these regions - Central and South America, Africa, Parts of Asia, The Pacific Islands, and Some parts of the United States. In short, dengue fever can affect anyone in regions where the virus is prevalent, with children and the elderly at a higher risk for serious illness if they get infected by dengue fever virus. 

Can One Be Immune to Dengue Fever? 

Yes, one can become immune to a specific strain of the dengue virus once they've been infected with it. However, there are four different strains of the dengue virus (DENV-1, DENV-2, DENV-3, and DENV-4). After one gets infected with one strain, they become immune to that strain. 

Our immune system has tools called antibodies that recognize and fight infections. These are specific to each virus, fitting them like a key fits a lock. Antibodies attach to the virus, and our immune system destroys it. Once our body knows how to fight a specific strain of the virus, we are unlikely to get sick from that same strain again. 

Diagnosis and Treatment of Dengue Fever

Diagnosis of Dengue Fever Virus

Doctors can diagnose dengue fever in the following steps:

• Medical History 
  • Mosquito Contact - They can ask about any recent contact with mosquitoes.
  • Travel History - They can check if one has traveled to areas where dengue is common.

• Physical Examination
  • Tourniquet Test - A tight band or blood pressure cuff is wrapped around the patient’s upper arm for a specific period to see if the patient has bleeding spots under the skin. 

• Laboratory Tests
  • Complete Blood Count (CBC) -This test checks a patient’s blood components. A low platelet count and increased red blood cell concentration may indicate dengue.
  • Immunological Tests - These tests look for specific antibodies or antigens related to the dengue virus, such as, 
    • Dengue NS1 Antigen - Detects the virus early in the infection.
    • Dengue IgM and IgG - Detect antibodies of one’s body produced in response to the virus.
  • PCR (Polymerase Chain Reaction) - This molecular test detects the genetic material of the dengue virus and identifies which of the four strains a patient has.

Treatment of Dengue Fever Virus 

• Once diagnosed, doctors aim to treat dengue fever and help patients recover quickly. Treatment focuses on managing symptoms and preventing complications.
• Using Intravenous (IV) Fluids - If a patient has significant fluid loss, persistent vomiting, diarrhea, or low blood pressure, the doctor gives fluids to a patient through a vein to replace lost fluids.
• Pain Relievers -  Medications like paracetamol (acetaminophen) can be given to patients to reduce fever and relieve muscle and joint pain.
• Oral Rehydration Salts (ORS) - These are given to replace lost fluids and prevent dehydration.
• Blood Transfusion - If a patient undergoes significant bleeding, either internally or externally, the doctor may give them a blood transfusion to prevent shock and manage blood loss.
• Patient Monitoring - Doctors frequently check patient’s blood to monitor platelet levels, white blood cell counts, and red blood cell concentration.

Preventive Measures of Dengue Fever 

To prevent dengue fever, follow these dengue fever prevention steps:

• Use Mosquito Repellent -  Apply repellents that contain DEET (20%-30%) or other EPA-registered ingredients to keep mosquitoes away.
• Wear Protective Clothing - Wear long sleeves, long pants, and socks. Especially when outdoors and at night, ensure that your skin is covered to prevent mosquito bites.
• Eliminate Breeding Sites - Remove standing water from containers such as buckets, bird baths, old tires, and any other places where water can collect.
• Netting on Doors - Install mosquito netting on doors to prevent mosquitoes from entering your home.
• Dengue Vaccine  - Recommended for individuals aged 4-60 years who have previously had dengue. This vaccine can reduce the risk of severe dengue if infected again by a different strain. It is not recommended for those who have never had dengue before, as it may increase the risk of severe dengue (antibody-dependent enhancement).
• Take Travel Precautions - Pregnant women and others should avoid traveling to areas where dengue is common if possible.

Which Healthcare Professional Research on Dengue?

Virologists are the ones who do advance research on dengue virus. To become a virologist, one has to do a bachelor's or master's in molecular biology. 

Colleges Offering Molecular Biology Courses and Corresponding Fees

You can use Docthub to find colleges that are offering molecular biology or microbiology courses. 

FAQs

How is Dengue fever transmitted? 

Dengue is primarily transmitted through the bites of infected Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus. These mosquitoes become carriers of the dengue virus after biting an infected person. 

How long do the symptoms last?

Dengue fever symptoms typically last between 2 to 7 days. Most people start to feel better after about a week. 

Can Dengue Fever be prevented?

Yes, dengue fever can be prevented through several measures to reduce mosquito bites and control mosquito populations. To learn more, read the preventive measures section of the blog. 

What are the complications of Dengue Fever?

Dengue fever can lead to severe complications like Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS), which involve severe bleeding, plasma leakage, and dangerously low blood pressure. Immediate medical attention is crucial for severe cases. 

How is Dengue Fever diagnosed?

The whole process of diagnosing dengue virus has been discussed in the blog. To know more, read the blog.