Dengue fever is a disease caused by one of a number of viruses that are carried by mosquitoes. These mosquitoes then transmit the virus to humans. It is also known as Dengue, dengue hemorrhagic fever (DHF). Homeopathy in dengue fever, Prevention of Dengue Fever
Description
The virus that causes dengue fever is called an arbovirus, which stands for arthropod-borne virus. Mosquitoes are a type of arthropod. In a number of regions, mosquitoes carry this virus and are responsible for passing it along to humans.
Dengue fever cannot be passed directly from one infected person to another. Instead, the virus responsible for dengue fever requires an intermediate vector, a mosquito, which carries the virus from one host to another. The mosquito that carries the arbovirus responsible for dengue fever is the same type of mosquito that can transmit other diseases, including yellow fever. This mosquito is called Aedes egypti. The most common victims are children younger than 10 years of age.
Etiology
Dengue is caused by Flavivirus. Flavivirus has four closely related, but antigenically distinct, virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), of the genus Flavivirus.
Infection with one of these serotypes does not provide cross-protective immunity, so persons living in a dengue-endemic area can have four dengue infections during their lifetimes.
Dengue is primarily a disease of the tropics. The viruses that cause it are maintained in a cycle involving humans and Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans. Infection with dengue viruses produces a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease.
Important risk factors for DHF include the strain and serotype of the infecting virus, as well as the age, immune status, and genetic predisposition of the patient.
Mechanism of Infection & symptoms
Dengue fever can occur when a mosquito carrying the arbovirus bites a human, passing the virus on to the new host. Once in the body, the virus travels to various glands where it multiplies. The virus can then enter the bloodstream. The presence of the virus within the blood vessels, especially those feeding the skin, causes changes to these blood vessels. The vessels swell and leak. The spleen and lymph nodes become enlarged, and patches of liver tissue die. A process called disseminated intravascular coagulation (DIC) occurs, where chemicals responsible for clotting are used up and lead to a risk of severe bleeding (hemorrhage).
After the virus has been transmitted to the human host, a period of incubation occurs which lasts for about 5-8 days. During this period, the virus multiplies.
Symptoms of the disease appear suddenly and include high fever, chills, headache, eye pain, red eyes, enlarged lymph nodes, a red flush to the face, lower back pain, extreme weakness, and severe aching in the legs and joints.
This initial period of illness lasts about 2-3 days. After this time, the fever drops rapidly and the patient sweats heavily. After about a day of feeling relatively well, the patient’s temperature increases again, although not as much as the first time. A rash of small red bumps begins on the arms and legs, spreading to the chest, abdomen, and back. It rarely affects the face. The palms of the hands and the soles of the feet become swollen and turn bright red. The characteristic combination of fever, rash, and headache are called the “dengue triad.”
Most people recover fully from dengue fever, although weakness and fatigue may last for several weeks. Once a person has been infected with dengue fever, his or her immune system keeps producing cells that prevent reinfection for about a year.
Prevention and treatment
No dengue vaccine is available. Recently, however, attenuated candidate vaccine viruses have been developed in Thailand. These vaccines are safe and immunogenic when given in various formulations, including a quadrivalent vaccine for all four dengue virus serotypes. Efficacy trials in human volunteers have yet to be initiated. Research is also being conducted to develop second-generation recombinant vaccine viruses; the Thailand attenuated viruses are used as a template. Therefore, an effective dengue vaccine for public use will not be available for 5 to 10 years.