Dengue Fever: Symptoms, Causes and Treatments

Dengue fever is a mosquito-borne illness that occurs in tropical and subtropical areas. Mild dengue causes a high fever and flu-like symptoms. Severe dengue, also called dengue hemorrhagic fever, can cause severe bleeding, a sudden drop in blood pressure (shock), and death. Dengue is caused by one of four related viruses: Dengue viruses 1, 2, 3, and 4.

Causes of Dengue Fever

The primary cause of dengue fever is four types of dengue viruses. One can’t get dengue fever from being around an infected person. Instead, dengue fever is spread through mosquito bites. When a mosquito bites a person infected with the dengue virus, the virus enters the mosquito. Then, when the mosquito bites another person, the virus enters the bloodstream and causes an infection.

Symptoms of Dengue

Symptoms of dengue fever are generally mild in younger children and those who have the disease for the first time. However, older kids, adults, and those with a previous infection may have moderate to severe symptoms.

Symptoms of dengue usually develop suddenly, about 5 to 8 days after one is infected, and the common symptoms include:

• A high temperature or feeling hot or shivery
• A severe headache
• Pain behind the eyes
• Muscle and joint pain
• Feeling or being sick
• A widespread red rash
• Abdomen pain
• Loss of appetite
• Persistent vomiting.
• Bleeding from your gums or nose
• Blood in your urine, stools, or vomit
• Bleeding under the skin, which might look like bruising
• Difficult or rapid breathing
• Fatigue

Severe Dengue

A patient enters the critical phase, usually about 3-7 days after illness onset. During the 24-48 hours of the crucial stage, a small portion of patients may manifest sudden deterioration of symptoms. At this time, the fever is dropping in the patient, warning signs associated with severe dengue.

Warning signs that doctors should look for include:

• Severe abdominal pain
• Persistent vomiting
• Rapid breathing
• Bleeding gums or nose
• Fatigue
• Restlessness
• Liver enlargement
• Blood in vomit or stool.

Transmission of Dengue Fever

This section explores the different modes through which dengue fever is transmitted, including human-to-mosquito transmission, maternal transmission, and other rare transmission routes.

Human-to-Mosquito Transmission

Mosquitoes can become infected by people who are viremic with DENV. This can be someone who has an asymptomatic dengue infection, someone who is yet to have an asymptomatic infection (they are pre-symptomatic), but also people who show no signs of illness as well (they are asymptomatic)

Human-to-mosquito transmission can occur up to 2 days before someone shows symptoms of the illness up to 2 days after the fever has resolved.

The risk of mosquito infection is positively associated with high viremia and high fever in the patient; conversely, high levels of DENV-specific antibodies are associated with a decreased risk of mosquito infection. Most people are viremic for about 4-5 days, but viremia can last 12 days.

Maternal Transmission

The primary mode of transmission of DENV between humans involves mosquito vectors. However, there is evidence of the possibility of maternal transmission (from a pregnant mother to her baby). While vertical transmission rates appear low, the risk of vertical transmission is seemingly linked to the timing of the dengue infection during pregnancy. When a mother does have a DENV infection when she is pregnant, babies may suffer from pre-term birth, low birth weight, and fetal distress.

Other Transmission Modes

Rare transmission cases via blood products, organ donation, and transfusions have been recorded. Similarly, the virus’s transovarial transmission within mosquitoes has also been recorded.

Three Stages of Dengue Fever

1. Febrile Phase:

The febrile phase marks the initial onset of dengue fever, with symptoms that usually begin suddenly. This phase typically lasts between 2 to 7 days, with individuals experiencing a high-grade fever, often around 40°C. Alongside the fever, common symptoms include a severe headache, eye pain (especially behind the eyes), joint and muscle aches, and nausea. Some individuals may notice a skin rash, as well as mild hemorrhagic manifestations such as petechiae (small red spots), gum bleeding, or nosebleeds. A few patients may also experience discomfort in the abdomen or tenderness in the upper abdominal region.

2. Critical Phase:

The critical phase occurs between the third and seventh day of infection, typically following the febrile phase. During this time, the fever begins to subside, but the risk of complications increases. The critical phase is marked by the body’s response to plasma leakage, which can lead to severe dehydration, shock, or organ dysfunction. Symptoms may include persistent vomiting, extreme fatigue, significant abdominal pain, and changes in blood pressure. Some patients may develop severe bleeding, with symptoms like bloody stools, vomit, or nosebleeds. This phase requires close medical monitoring, as it may rapidly progress to life-threatening conditions, including shock and disseminated intravascular coagulation (DIC).

3. Recovery Phase:

The final stage of dengue fever is the recovery phase. This phase is characterized by the gradual stabilization of vital signs and the reabsorption of the extravascular fluid that accumulated during the critical phase. As the body recovers, the fever subsides completely, and blood pressure, pulse rate, and urine output begin to normalize. Patients often show signs of improvement, such as increased appetite and a reduction in abdominal swelling. However, some may experience minor symptoms like skin rashes or temporary fatigue as the body heals completely. The recovery phase typically lasts a few days to a week, with patients slowly regaining their strength.

Treatment for Dengue Fever

There is no specific medicine to treat dengue infection. But you can follow the below

• See a doctor
• Plenty of water intake
• Take rest
• Use pain relievers

Preventing Dengue Fever

The best way to prevent the disease is to prevent bites from infected mosquitoes, mainly if you are living in or traveling to a tropical area. This involves protecting yourself and making efforts to keep the mosquito population down. In 2019, the FDA approved a vaccine called Dengvaxia to help prevent the disease from occurring in adolescents aged 9 to 16 who have already been infected by dengue. But, there currently is no vaccine to prevent the general population from contracting it.

To Protect Yourself:

• Use mosquito repellents, even indoors.
• When outdoors, wear long-sleeved shirts and long pants tucked into socks.
• When indoors, use air conditioning if available.
• Make sure window and door screens are secure and free of holes. If sleeping areas are not screened or air-conditioned, use mosquito nets.
• If you have symptoms of dengue, speak to your doctor.

Frequently Asked Questions