Dengue fever

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Dengue fever is a mosquito-borne viral infection that causes flu-like symptoms and can lead to potentially lethal complications. It is transmitted by the bites of infected female Aedes mosquitoes, primarily the Aedes aegypti species. Symptoms typically begin 3-14 days after infection and may include high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen glands, and rash. While many cases are mild and self-limiting, dengue can progress to severe dengue (also known as dengue hemorrhagic fever), which is characterized by severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, and fatigue. Severe dengue is a medical emergency that can result in circulatory shock, severe bleeding, organ impairment, and even death. For example, a person infected with dengue may initially experience a high fever and headache, but if left untreated, their condition could rapidly deteriorate, leading to internal bleeding and organ failure.

Prevention of dengue primarily involves controlling mosquito populations and protecting individuals from mosquito bites. This can be achieved through the use of insect repellents, wearing protective clothing, installing window screens, and eliminating mosquito breeding sites. In addition, a dengue vaccine called Dengvaxia has been developed and is approved for use in several countries. However, the vaccine is only recommended for individuals with a documented history of previous dengue infection, as it may increase the risk of severe dengue in those who have never been infected before. Researchers are working on developing new vaccines that can provide broader protection against all four dengue virus serotypes.

Terms

• Aedes mosquito: A genus of mosquito that is the primary vector for transmitting dengue virus to humans. These mosquitoes are easily recognizable by the white markings on their legs and are found in tropical and subtropical regions worldwide.
  Example: The Aedes aegypti mosquito is the main carrier of the dengue virus in many countries.

• Dengue virus: A single-stranded RNA virus belonging to the Flaviviridae family that causes dengue fever. There are four distinct serotypes of the virus (DENV-1, DENV-2, DENV-3, and DENV-4).
  Example: Infection with one dengue virus serotype provides lifelong immunity against that specific serotype but not against the others.

• Dengue hemorrhagic fever (DHF): A severe form of dengue infection characterized by high fever, damage to lymph and blood vessels, bleeding from nose and gums, enlargement of the liver, and circulatory failure. It can be fatal if not promptly treated.
  Example: The risk of developing dengue hemorrhagic fever is higher in individuals who have previously been infected with a different dengue serotype.

• Flaviviridae: A family of positive-sense single-stranded RNA viruses that includes the dengue virus, along with other notable viruses such as Zika, West Nile, and yellow fever viruses.
  Example: Viruses in the Flaviviridae family are primarily transmitted to humans through the bites of infected arthropods, such as mosquitoes and ticks.

• Vector: An organism that transmits pathogens and parasites from one infected person (or animal) to another, causing serious diseases in human populations.
  Example: Mosquitoes are vectors for various diseases, including dengue fever, malaria, and Zika virus disease.

Analogy

Imagine a bustling city where a group of thieves (the dengue viruses) is on the loose. These thieves are crafty and can only be transported by a specific type of getaway car (the Aedes mosquito). When an unsuspecting person is bitten by an infected mosquito, it's like the thief has been dropped off at their doorstep. Once inside the body, the virus begins to multiply, causing symptoms that can range from mild (like a simple break-in) to severe (like a full-scale heist targeting vital organs). Just as a city would take measures to prevent crime and apprehend the thieves, preventing dengue involves taking steps to control mosquito populations and protecting oneself from bites. In this analogy, the police and emergency services represent the immune system and medical care that work to fight off the infection and prevent severe complications.

Misconception

One common misconception about dengue fever is that it is a one-time illness. Many people believe that once they have been infected with dengue, they develop lifelong immunity against the disease. However, this is not entirely true. There are four distinct serotypes of the dengue virus, and while infection with one serotype does provide lifelong immunity against that specific type, it does not protect against the other three. In fact, subsequent infections with different serotypes can actually increase the risk of developing severe dengue.

For example, let's say a person gets infected with DENV-1 and recovers. A few years later, they travel to another country and get bitten by a mosquito carrying DENV-2. Because their immune system has previously encountered a dengue virus, it mounts a rapid response. However, this response can be exaggerated and lead to a more severe form of the disease. This phenomenon is known as antibody-dependent enhancement (ADE) and is one of the reasons why developing a dengue vaccine has been so challenging.

History

1. 1779: The first recorded dengue epidemic occurred in Asia, Africa, and North America.

2. 1906: The term "dengue" was coined, derived from the Swahili phrase "Ka-dinga pepo," meaning "cramp-like seizure caused by an evil spirit."

3. 1943-1944: The first dengue epidemics were recorded in the Pacific during World War II, affecting both military and civilian populations.

4. 1950s-1970s: Dengue began to spread globally due to rapid urbanization, population growth, and increased international travel.

5. 1981: The first major dengue hemorrhagic fever epidemic occurred in Cuba, with over 300,000 cases reported.

6. 1997: The World Health Organization (WHO) published the first comprehensive guidelines for dengue prevention and control.

7. 2000-2020: Dengue continued to spread rapidly, with the number of reported cases increasing eightfold over the past two decades. The disease is now endemic in more than 100 countries, with an estimated 390 million infections occurring annually. In recent years, several countries have experienced explosive outbreaks, such as the 2019 epidemic in the Philippines, which recorded over 420,000 cases and 1,500 deaths.

How to use it

1. Prevention: The best way to protect yourself from dengue is to prevent mosquito bites. When traveling to or living in dengue-endemic areas, use insect repellent containing DEET, wear long-sleeved shirts and pants, and stay in well-screened or air-conditioned rooms. Eliminate mosquito breeding sites by emptying standing water from containers such as flowerpots, buckets, and old tires.

2. Recognizing symptoms: Familiarize yourself with the symptoms of dengue fever, such as high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, and rash. If you suspect you have dengue, seek medical attention immediately, especially if you develop warning signs of severe dengue like severe abdominal pain, persistent vomiting, or bleeding.

3. Supporting community efforts: Participate in community-based dengue prevention programs, such as those that aim to raise awareness about the disease and its prevention. Support local vector control efforts, like the use of insecticides and the elimination of mosquito breeding sites in public areas. By working together, communities can reduce the risk of dengue outbreaks and protect public health.

Facts

• Dengue is the fastest-spreading mosquito-borne viral disease, with a 30-fold increase in global incidence over the past 50 years.

• The global annual economic cost of dengue is estimated at $8.9 billion.

• In 2019, the Philippines declared a national dengue epidemic, with over 420,000 cases and 1,500 deaths reported.

• A person can get dengue up to four times in their lifetime, once for each of the four dengue serotypes.

• The Aedes aegypti mosquito, the primary vector for dengue, can lay eggs in water volumes as small as a bottle cap.