What Is Dengue Fever?
Introduction
Dengue is an infectious disease caused by dengue viruses, which are transmitted to humans by mosquitoes. The rising level of dengue infections has become a serious international concern. When was dengue first reported, and how was the disease named? What are the symptoms of dengue? Is there a cure? In this section, we will explore the answers to these questions.
Dengue Facts
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 nonurban areas, but dengue infections are increasing in rural communities.

Figure 1: Countries and areas at risk of dengue transmission in 2007
The countries and areas at risk of dengue transmission are shaded in orange, and the geographical extension of dengue is indicated in red. Data are from the World Health Organization, 2007.
© 2010 Nature Publishing Group Guzman, M. G. et al. Dengue: A continuing global threat. Nature Reviews Microbiology 8, S7–S16 (2010). All rights reserved.

History of Dengue
Where did dengue originate? The origin of dengue is unclear, but scientists have recently proposed that dengue originated in Asian forests in an infectious cycle involving mosquitoes and primates. As early as 992, a dengue-like outbreak in humans was recorded in a Chinese medical encyclopedia. Epidemics of dengue-like illnesses were reported in the French West Indies in 1635 and in Panama in 1699.

In 1771, Dr. Jose Sabater, a physician at the military hospital in San Juan, Puerto Rico, recommended treating dengue with small quantities of rum. At the time, the disease was called “break-bone fever.” Where did this name come from? As you might guess, patients with the disease experienced a high fever accompanied by such severe bone and joint pains that they felt their bones were breaking.

In 1780, Dr. Benjamin Rush recorded an epidemic of the disease later known as dengue in Philadelphia, Pennsylvania. Rush described the symptoms of patients with the disease, which he called “bilious remitting fever.” These symptoms included fever, joint and muscle pain, headache, rash, weakness, nausea, vomiting, and bleeding.

As early as 1801, people called the disease “dengue.” In a letter written by Queen Luisa of Spain during her recovery from a dengue infection in 1801, she said, “I’m feeling better, because it has been the cold in fashion, that they call dengue, and since yesterday I’ve had some blood, which is what is making me uncomfortable, and after talking some time the throat hurts.” What does dengue mean? The word dengue is Spanish for “affectation,” “careful,” or “fastidious.” The term probably described the cautious, stiff movements of patients suffering from the muscle, bone, and joint pain caused by dengue fever. Some researchers believe that the name came from a Swahili phrase Ka dinga pepo, or a disease caused by an evil spirit.

In 1818, there was a serious dengue epidemic in Peru — 50,000 people were stricken with the illness. The first recorded dengue pandemic occurred between 1827 and 1828, and it affected the Virgin Islands, Jamaica, Cuba, Venezuela, the United States, and Mexico. Pandemics are epidemics that affect a very large region, multiple countries, or even the entire globe. Later in the 1800s, epidemics plagued Brazil, the southern United States, and the Caribbean. Dengue epidemics continued to occur more often through the first half of the 1900s. During World War II, dengue spread to new regions as large numbers of soldiers were stationed throughout the world. The first epidemic of severe dengue was reported in Manila, Philippines, in 1953, and the disease continued to spread in Southeast Asia during the next 20 years. Due to organized efforts to eliminate dengue in Central America and South America, fewer dengue epidemics occurred in these areas during the 1960s and 1970s, but when these efforts ended, dengue infections returned to these regions.

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?


Figure 2: Dengue fever symptoms
The symptoms of dengue include a fever, headache, severe body and joint pain, and a rash.
© 2011 Nature Education All rights reserved.
Doctors often have trouble diagnosing dengue because its symptoms can vary widely. Some patients show no symptoms at all. Babies and young children infected with the dengue virus typically have mild symptoms such as a fever and a rash over their entire bodies, but no other symptoms of dengue. Older children and adults may also have these mild symptoms, or they may have classic symptoms of dengue, including a high fever that lasts for two to seven days, severe pain in the muscles, bones, and joints, pain behind the eyes, severe headaches, nausea and vomiting, and a rash (Figure 2). Dengue fever is characterized by a fever response with two peaks. Near the beginning of the infection, the patient experiences a very high body temperature, which then starts to drop and suddenly climbs again for a second time.
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.

Severe Dengue
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?
Currently, there is no cure or specific medication to treat 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.
Summary
Approximately 2.5 billion to 3 billion people around the world are currently at risk of dengue infections. The symptoms of dengue can vary widely, although some patients have no symptoms at all. The classic symptoms of dengue include a high fever, severe pain in the muscles, bones, and joints, pain behind the eyes, severe headaches, nausea and vomiting, and a rash. Most patients recover from dengue infections with rest and fluids. Some patients develop severe dengue, a more serious condition that occurs when blood plasma leaks through the capillaries. Severe dengue can lead to internal bleeding, shock, and organ failure. When treated quickly with intravenous fluid replacement, most patients recover from severe dengue. There is currently no cure for dengue and no vaccine to prevent dengue infections.
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