After the death of brutal terrorist Prabhakaran, Sri Lankans tend to believe that he has been rebirth as a mosquito in Aedes genus. The latest controversy in Sri Lanka is the epidemic of dengue fever all over the country mostly in Western, Wayamba, Central and Southern provinces. Currently more than 130 people including children have died due to the infection of fatal dengue virus.
What is dengue fever?
Dengue fever and dengue hemorrhagic fever (DHF) are acute febrile diseases, caused by four antigenically different but closely related, virus serotypes* (DEN-1, DEN-2, DEN-3, and DEN-4), found in the tropical and sub tropical areas. These four dengue serotypes are undergoing in a cycle that involves humans and Aedes aegypti mosquitoes or more rarely the Aedes albopictus mosquito. Because of these four different serotypes, it is possible to get dengue fever multiple times. But in each attack of dengue, the immune system produces antibodies against that particular serotype to which the patient was infected.
Dengue fever is also known as "breakbone" and "dandy fever". Victims of dengue often suffer due to the pain in joints and muscles, hence the name breakbone fever. Slaves in the West Indies call dandy fever due to the postures and gait of infected patients.
* Serotypes - closely related set of viruses that can be differentiated by the immune responses that they produced.
Group - IV single stranded (+) RNA
Family - Flaviviridae
Genus - Flavivirus
Little bit about Aedes aegypti and Aedes albopictus…..
Aedes aegypti , and Aedes albopictus are the most common Aedes species which include domestic, day-biting mosquitoes that feed on humans.A.albopictus species is also known as Asian Tiger Mosquito. White spots in all over the body are a significant feature of Aedes mosquitoes. They dwell during rainy seasons but can breed in water-filled flower pots, plastic bags, coconut husks, yogurt cups, old tires and cans throughout the year. The Aedes aegypti mosquito is a daytime biter with dominant periods of biting around sunrise and sunset. It may bite at any time of the day and is often hidden inside homes or other dwellings, especially in urban areas.
Kingdom - Animalia
Phylum - Arthropoda
Class - Insecta
Order - Diptera
Family - Culicidae
Genus - Aedes
Subgenus - Stegomyia
Species - Aedes aegypti / Aedes albopictus
Dengue is found throughout the tropics and subtropics. A wide range of geographical spreading includes Asian countries like Singapore, Malaysia, Taiwan, Thailand, Vietnam, Indonesia, Philippines, Pakistan, India, Sri Lanka, Maldives, Bangladesh and South Pacific, West Indies, South American and African countries like northern Australia ,northern Argentina, Costa Rica, , Mexico, Suriname, Puerto Rico, Jamaica, Bolivia, Brazil, Guyana, Venezuela, Barbados, Trinidad and Samoa.
According to the World Health Organization (WHO), each year they estimate 50 million cases of dengue fever with 500,000 cases of dengue hemorrhagic fever all over the world. Nearly 40% of the world's population lives in an area endemic with dengue. The disease is now epidemic in more than 100 countries.
The first reported simultaneous epidemic occurred in 1779-1780 on three continents Asia, Africa and North America. This indicates that more than 200 years ago these viruses and their mosquito vector have had a worldwide distribution in the tropics. During that time, dengue fever was recognized as a mild, nonfatal disease. Normally, between major epidemics, there were long intervals like 10-40 years. This is mainly because the introduction of a new serotype into a population occurred only if mosquito vectors could transport between populations by sailing.
After World War II, an epidemic of dengue reported in Southeast Asia and has spread around the world since then. Epidemics caused by multiple serotypes are more frequent because the geographic distribution of dengue viruses and their mosquito vectors has expanded. And dengue hemorrhagic fever (DHF) has aroused in the Pacific region and America. Epidemic DHF first appeared at 1950s in Southeast Asia, but from 1975 it devastated the lifestyle of people in Southeast region becoming a frequent cause of hospitalization and deaths.
What is typical dengue fever?The most important thing is that the typical dengue does not cause any death. It is fatal in less than 1% of cases. The severe phase of the typical dengue with fever and myalgias lasts about one to two weeks. At the first stage of recovery, a feeling of weakness (asthenia) is remained, and full recovery often takes several weeks.
What is dengue hemorrhagic fever?DHF is a specific syndrome that shows its affection in children, aged fewer than 10 and it causes abdominal pain, hemorrhage (bleeding), and circulatory shock. Therefore DHF is also called as dengue shock syndrome. Infants under a year of age are especially at risk of dying from DHF. The mortality (death rate) of DHF is considerable. It is in the range from 6%-30%. Most of the deaths occur in children.
How is dengue infected?The Flavivirus is infected after biting of an Aedes aegypti or rarely Aedes albopictus mosquito which has previously bitten an infected person. One mosquito bite can infect the disease. The Flavivirus is not contagious and so it cannot be infected directly from person to person. Therefore there must be a person-to-mosquito-to-another-person pathway.
What are the signs and symptoms?After being bitten by a mosquito carrying the Flavivirus, the incubation period of the virus ranges from 3 to15 (generally 5 to 8) days. Dengue starts with chills, headache, pain upon moving the eyes and low backache. Legs and joints aches occur and the temperature rises quickly as high as 104° F (40° C), with relative low heart rate (bradycardia) and low blood pressure (hypotension). The eyes become reddened. A flushing or pale pink rash comes over the face and then disappears. The glands (lymph nodes) in the neck and groin are become swollen. Fever continues for two to four days, followed by rapid drop in temperature (defervescence) with utmost sweating. Before this a period with normal temperature and a sense of well-being lasts about a day. Along with the second rapid rise in temperature, a characteristic rash appears and spreads from the extremities to cover the entire body except the face. Bright red and swollen palms and soles may be appeared.
At the initiative level in DHF, it starts with high continuous fever and headache and later it shows respiratory and intestinal symptoms including sore throat, cough, nausea, vomiting and abdominal pain. The circulatory shock occurs two to six days after occurring the symptoms like sudden collapse, weak pulse, cool and clammy extremities (but the trunk is often warm) and blueness around the mouth (circumoral cyanosis).And also in DHF we can see apparent symptoms like bleeding with easy bruising, bleeding gums, nosebleed (epistaxis), blood spots in the skin (petechiae), spitting up blood (hematemesis), and blood in the feces (melena). There is a high opportunity in infecting Pneumonia and inflammation of the heart (myocarditis) can be occured.
What are the treatments?There is no specific medicine or antibiotic to treat dengue because it is caused by a virus. There is a vaccine undergoing clinical trials, but there are no proofs that it will be safe or effective.
For typical dengue, the treatment is purely concerned to give relief for the symptoms. It is important to rest and intake fluid to adequate hydration. Aspirin and non-steroidal anti-inflammatory drugs should be avoided. Acetaminophen (Tylenol) and codeine may be given for severe headache and for the joint and muscle pain (myalgia).
Patients with DHF must be monitored tightly for first few days because unobservant shock may occur or recur. Cyanotic (bluish) patients are given oxygen. Vascular collapse (shock) requires immediate fluid replacement. Bleed controlling can be done by transfusion of blood.
How can dengue fever be prevented?The Aedes aegypti mosquito is dominant in daytime with peak periods of biting around sunrise and sunset. It can bite at any time of the day and is often hidden inside homes or other dwellings, especially in urban areas. The transmission of the virus to mosquitoes must be restricted to prevent the illness. For that patients are kept under mosquito netting until the second active term of fever is over and then they are no longer contagious.
The prevention of dengue needs control or eradication of the mosquito vectors that carry the Flavivirus. People in the nations, pandemic by dengue fever are urged to empty stagnant water from the places where water can be collected like old tires, trash cans, plastic bags, coconut husks, yogurt cups and flower pots. Governments of epidemic countries also initiate for the eradication of mosquitoes.
For personal protection, wear long pants and long sleeves, use mosquito repellent sprays when visiting places where dengue is endemic. Limiting exposure to mosquitoes and clean regularly the places where standing water can be collected will help for the dengue prevention.
The future Outlook of Dengue.At this moment no dengue vaccine is available. But recently, attenuated candidate vaccine viruses have been developed. Efficacy trials using human volunteers have yet to be started. There is a research being conducted to create second-generation recombinant vaccine* viruses. So an effective dengue vaccine will not be available for 5 to 10 years for public use.
Recombinant vaccine* -creating an attenuated virus using the technique of recombination which exposes an immune response against the particular viral strain and then can be used as a vaccine for humans.
http://www.phac-aspc.gc.ca/tmp-pmv/2007/dengue070823_e.html
http://www.who.int/tdr/publications/publications/pdf/planning_dengue.pdf
http://www.cdc.gov/ncidod/dvbid/dengue/ http://www.medicinenet.com/dengue_fever/page3.htm
http://en.wikipedia.org/wiki/Dengue_fever#Diagnosis
http://www.cdc.gov/NCIDOD/DVBID/DENGUE/
