Dengue fever is a painful, debilitating mosquito-borne disease caused by any one of four closely related dengue viruses. These viruses are related to the viruses that cause West Nile infection and yellow fever.
Each year, the World Health Organization reports that approximately 50 million people are infected with dengue, although some researchers estimate that this number could be as high as 100 million. Typically, dengue causes a severe flu-like illness with high fever, headache, and severe body and joint pains. Most patients recover from dengue infections.
A more dangerous form of dengue infection, however, called severe dengue, hospitalizes an estimated 500,000 people — most of them children — every year. In some regions of the world, severe dengue is fatal for more than 5% of patients. An estimated 2.5 billion to 3 billion people around the world are currently at risk of dengue infections, and most of these people live in tropical, urban regions of Southeast Asia, the Americas, Africa, and the Pacific (Figure 1). The risk of dengue is higher in urban regions than in non-urban areas, but dengue infections are increasing in rural communities.
History of Dengue
Dengue viruses have been on the march for more than 100 years. Dengue originated in monkeys and spilled over into humans as long as 800 years ago. It was restricted to Africa and Southeast Asia until the mid-20th century. The dengue viruses in viremic individuals and their Aedes aegypti mosquito vectors spread throughout tropical Southeast Asia via maritime shipments.
In 1943, Ren Kimura and Susumu Hotta first isolated the dengue virus. These two scientists were studying blood samples of patients taken during the 1943 dengue epidemic in Nagasaki, Japan.
Rising Dengue Infections
In recent years, the number of dengue cases reported to the World Health Organization has risen dramatically. Dengue is becoming a greater threat to public health than it has been in the past. Epidemics have occurred in nearly all tropical and some subtropical regions of the world. Dengue has spread to new countries, including Nepal and Bhutan, and the incidence of dengue has increased thirty-fold since the 1960s. Why are dengue outbreaks becoming more frequent? This increase in dengue transmission may be due to a number of factors, including population growth, more long-distance travel, growing urban areas, lack of sanitation, and poor mosquito control. The higher numbers may also be the result of better surveillance and official reporting of dengue cases. The rapid spread of dengue is a serious international concern.
What Are the Symptoms of Dengue Fever?
Symptoms, which usually begin four to six days after infection and last for up to 10 days, may include:
- Sudden, high fever (105 degree)
- Severe headaches
- Pain behind the eyes
- Severe joint and muscle pain
- Skin rash, which appears two to five days after the onset of fever
- Mild bleeding (such a nose bleed, bleeding gums, or easy bruising)
Sometimes, symptoms are mild and can confuse for those of the flu or another viral infection. Younger children and people who have never had the infection before tend to have milder cases than older children and adults. However, serious problems can develop. These include dengue hemorrhagic fever, a rare complication characterized by high fever, damage to lymph and blood vessels, bleeding from the nose and gums, enlargement of the liver, and failure of the circulatory system. The symptoms may progress to massive bleeding, shock, and death. This is called dengue shock syndrome (DSS).
Other symptoms of dengue fever include a decrease in the number of white blood cells and a low level of platelets in the blood. Patients with dengue fever may have skin hemorrhages (bleeding under the surface of the skin) that appear as red or purple spots on the body. Dengue fever can also cause bleeding from the skin, nose, and gums. Recovery from dengue fever is often lengthy, lasting several weeks, and patients can experience lingering fatigue and depression.
People with weakened immune systems as well as those with a second or subsequent dengue infection can get at greater risk for developing dengue hemorrhagic fever.
Infection with the dengue virus can also cause a disease called severe dengue, which is more serious than dengue fever. Although the early symptoms of severe dengue are similar to dengue fever, severe dengue has a much higher death rate. As with dengue fever, patients with severe dengue have a high fever, experience bleeding, and have a reduced white blood cell count. What makes severe dengue more serious than dengue fever?
The major symptom of severe dengue is leakage of blood plasma out of the capillaries. This leakage occurs 24 to 48 hours after the patient’s fever drops, a period doctors refer to as the critical phase. Patients who improve after their fever drops are said to have dengue, but patients who deteriorate have severe dengue. In people with severe dengue, the escape of the plasma from the circulatory system can cause fluids to collect in body cavities. Scientists can detect plasma leakage by observing a higher-than-normal concentration of red blood cells and an abnormally low protein level in the blood. Another sign of severe dengue is severe bleeding. In some cases, stomach and intestinal bleeding can cause death. In addition, patients with severe dengue have a tendency to bruise easily and experience changes in blood pressure and pulse rate. Most patients recover from severe dengue with intravenous fluid replacement.
What happens if a patient with severe dengue is not treated?
The loss of plasma and protein can cause the patient to experience a condition called shock. Patients in shock show signs of circulatory failure. The lack of blood circulation causes the patient to have cold, clammy, bluish skin. Patients experiencing shock seem restless, and their blood pressure and pulse may be undetectable. Severe dengue can also lead to respiratory distress and injury of other organs. If untreated, shock can lead to death within 24 hours, but if treated quickly with intravenous fluid replacement, patients can recover.
Is There a Cure for Dengue Infections?
Individuals who believe that they may have dengue should consult a physician. The pain symptoms associated with dengue can be managed with pain relievers that do not increase the risk of bleeding. In addition, dengue patients require rest and fluids. It is important that patients with dengue be carefully monitored for signs of severe dengue so that they can be treated with fluid replacement in a timely manner and make a full recovery.
Diagnosing Dengue Fever
Doctors can diagnose dengue infection with a blood test to check for the virus or antibodies to it. If you become sick after traveling, let your doctor know. This will allow your doctor to evaluate the possibility that your symptoms can be a dengue infection.
Treatment for Dengue Fever
There is no specific medicine to treat dengue infection. If you think you may have dengue fever, you should rest, drink plenty of fluids and see a doctor. If you start to feel worse in the first 24 hours after your fever goes down, you should get to a hospital immediately to be checked for complications.
Preventing Dengue Fever-
The best way to prevent the disease is to prevent bites by infected mosquitoes. 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.
- To reduce the mosquito population, get rid of places where mosquitoes can breed. Regularly change the water in outdoor bird baths and pets’ water dishes, emptying stagnant water from buckets.
If someone in your home gets dengue fever, be especially vigilant about efforts to protect yourself and other family members from mosquitoes. Mosquitoes that bite the infected family member could spread the infection to others in your home.