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Introduction    Causes of Dengue    Sign and symptoms    The cycle of Dengue    Diagnosis of Dengue    Treatment of Dengue    Prevention and Control of Dengue    Recent outbreak of Dengue in Delhi    History of Dengue    Dengue and Chikungunya     Introduction  According to the World Health Organization's estimates released on January 25, 2012, over 2.5 billion people - over 40% of the world's population are now at risk from dengue. WHO estimates there may be 50-100 million dengue infections worldwide annually. Before 1970, only nine countries had experienced severe dengue epidemics. The disease is endemic in more than 100 countries. Cases across the Americas, south-east Asia and western Pacific have exceeded 1.2 million cases in 2008 and over 2.2 million in 2010.   In 2010, 1.6 million cases of dengue were reported in the Americas alone, of which 49 000 were severe dengue. An estimated 500, 000 people with severe dengue require hospitalization each year, a large proportion of whom are children. About 2.5% of those affected die, says the WHO. According to a Union health ministry note, dengue has been identified as one of the 17 neglected tropical diseases by the UN body. It has been listed among the 40 emerging diseases of global importance.   Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans, is the most common Aedes species. Infections produce a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. Some 2500 million people,  two fifths of the world's population are now at risk from dengue. Unprecedented population growth, mostly in developing tropical countries, has resulted in enormous urban sprawl, and unsanitary housing, water, sewage and waste systems. The result has been more  mosquitoes living closer to more  people. Now, dengue is the most important mosquito-borne viral disease  affecting humans; its global distribution is comparable to that of malaria, and an estimated 2.5 billion people live in areas at risk for epidemic transmission. In 2003 more than 220 people have been killed by two mosquito-borne viruses in India's largest state U.P. alone in three months.  Now in September 2010 the epidemic of Dengue is spreading rapidly all over India and more in Delhi. WHO currently estimates there may be 50 million cases of dengue infection worldwide every year.   Dengue is a very fatal disease. The worst thing is that there is no specific medicine to treat dengue. However, if proper steps are taken, then one can recover within two weeks.

Aedes aegypti  mosquitoes          Eggs of Aedes       Do you know ? * According to the WHO estimates released on January 25, 2012, over 2.5 billion people - over 40% of the world's population  are now at risk from dengue. * Dengue fever is a viral disease common in the  tropics, particularly in areas where mosquitoes   are not controlled.   * Dengue fever is transmitted by the bite of an  Aedes aegypti  mosquito.    * The disease is now endemic in more than 100 countries including India. It is a day biter.  * Symptoms: Severe joint pain, high fever, headache  backache, nausea and vomiting  *Danger: Internal bleeding or shock  *Treatment: Fluids; acetaminophen for pain, fever      .

Causes of Dengue    Dengue is a mosquito-borne seasonal viral infection infection caused by any one of four closely related viruses ((DENV 1-4 or DEN-1, DEN-2, DEN-3 or DEN-4).  Dengue viruses are transmitted to humans through the bites of infected female Aedes aegypti mosquitoes. These domestic mosquitoes thriving around human habitations typically bite in daylight hours.   Mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for 8-10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus, to susceptible individuals for the rest of its life. Infected female  mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of virus to humans has not yet been delineated.  Humans are the main amplifying host of the virus, although studies have shown that in some parts of the world monkeys may become infected and perhaps serve as a source of virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for two to seven days, at approximately the same time as they have fever; Aedes mosquitoes may acquire the virus when they feed on an individual during this period.    As the  major global demographic changes have occurred, the most important of which have been uncontrolled urbanization and concurrent population growth. These demographic changes have resulted in substandard housing and inadequate water, sewer, and waste management systems, all of which increase Aedes aegypti population densities and facilitate transmission of Aedes  aegypti borne disease.  Changing life styles, in particular the spread of non-degradable plastic packaging, which makes ideal larval habitats for Aedes aegypti mosquitoes. Another factor is the dramatic increase in automobiles and discarded tires, which are equally useful to mosquito larva. Increased commercial air travel is ideal for transporting dengue viruses (they travel inside their human victims) between population centers. Lastly, effective mosquito control is virtually nonexistent in most dengue-endemic in most of countries including India.   Sign and symptoms   After the virus enters the human body, it takes 4-6 days for the symptoms  to become visible. The main symptoms of dengue are high fever (103-105 degrees fahrenheit), severe headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash, and mild bleeding from nose or gums. Because of severe joint pain, dengue is also known as break-bone fever.   The symptoms, following an incubation period of five to eight days, are high fever, chills, severe headache, pain in the joints, nausea and vomitting, eye pain sweating, and prostration. Symptoms subside in two to seven  days, but after a remission lasting from a few hours to two days there is another rise in temperature, and a generalized  rash appears. Convalescence is sometimes prolonged, with weakness and low blood pressure.    While the initial symptoms are similar to those in dengue, in dengue haemorrhagic fever, small purplish spots appear on the skin, which is caused by blood leaking out of the vessels. This is caused by the decrease in  platelets, the cells in blood that help to stop bleeding.   The smallest blood vessels (capillaries) become excessively permeable (leaky) allowing the fluid component to escape from the blood vessels to organs of the body. As the disease progresses, large bruises appear on the patient's body and bleeding happens in the stomach with the patient vomiting blood. Severe haemorrhage may lead to failure of the circulatory system and shock, which might also cause death.    The cycle of Dengue   Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for the mosquitoes. The viruses are transmitted from human to human through the bites of the female Aedes mosquitoes, which acquire it while feeding on the blood of an infected person.

Diagnosis of Dengue   The diagnosis of dengue is usually made clinically. There exists a WHO definition of dengue haemorrhagic fever; all four criteria must be fulfilled: Fever:  Haemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea)  Thrombocytopaenia:  (Less than 100 platelets per mm³ or estimated as less than 3 platelets per high power field)   Evidence of plasma leakage (haematocrit more than 20% higher than expected, or drop in haematocrit of 20% or more from baseline following IV fluid, pleural effusion, ascites, hypoproteinaemia)   Dengue shock syndrome is defined as dengue haemorrhagic fever plus: Weak rapid pulse, and Narrow pulse pressure (less than 20 mm Hg)  or, Hypotension for age; Cold, clammy skin and restlessness.  Serology and PCR (polymerase chain reaction) studies are available to confirm the diagnosis of dengue if clinically indicated. Treatment of Dengue > There is no specific medication for treating a dengue infection or DHF.  However, careful clinical management by experienced physicians and nurses frequently saves the lives of DHF patients. With appropriate intensive supportive therapy, mortality may be reduced to less than 1%. Maintenance of the circulating fluid volume is the central feature of DHF case management.   Antibiotics do not help and generally paracetamol is the drug of choice to bring down fever and joint pain. Other medicines like aspirin and Brufen or any medicine that can decrease the platelet count should be avoided, since they can increase the risk of bleeding. As it has no specific medication, most patients with dengue fever can be treated at home. Those who are suffering from dengue should have proper bed rest, drink lots of fluids and water and take medicines to reduce fever.   Prevention and Control of Dengue   At present, the only method of controlling or preventing dengue and DHF is to combat the vector mosquitoes. In Asia and the Americas, Aedes aegypti breeds primarily in man-made containers like earthenware jars, metal drums and concrete cisterns used for domestic water storage, as well as discarded plastic food containers, used automobile tyres and other items that collect rainwater. In Africa it also breeds extensively in natural habitats such as tree holes and leaf axils. In recent years, Aedes albopictus, a secondary dengue vector in Asia, has become established in: the United States, several Latin American and Caribbean countries, in parts of Europe and in one African country. The rapid geographic spread of this species has been largely attributed to the international trade in used tyres. Vector control is implemented using environmental management and chemical methods. Proper solid waste disposal and improved water storage practices, including covering containers to prevent access by egg laying female mosquitoes are among methods that are encouraged through community- based programmes.   The application of appropriate insecticides to larval habitats, particularly those which are considered useful by the householders, e.g. water storage vessels, prevent mosquito breeding for several weeks but must be re-applied periodically. Small, mosquito-eating fish and copepods (tiny crustaceans) have also been used with some success. During outbreaks, emergency control measures may also include the application of insecticides as space sprays to kill adult mosquitoes using portable or truck- mounted machines or even aircraft. However, the killing effect is only transient, variable in its effectiveness because the aerosol droplets may not penetrate indoors to microhabitats where adult mosquitoes are sequestered, and the procedure is costly and operationally very demanding. Regular  monitoring of the vectors' susceptibility to the most widely used insecticides is necessary to ensure the appropriate choice of chemicals. Active monitoring and surveillance of the natural mosquito population should accompany control efforts in order to determine the impact of the programme.  You can help to control Dengue:   1. Change water in your room cooler every day or at least after 3 days.  2. Add two spoonful of petrol or kerosene to stagnant water every week to check mosquito.   3. Avoid the use of potted plants. If you have them at home, change water every alternative days.   4  Be careful about storing pails and watering cans.  5  You should keep the surrounding environment of your house and office clean.   Recent outbreak of Dengue in Delhi      Recent Dengue toll reported on September 17, 2010 the number of dengue cases in Delhi has gone up to 2,153 . With about 2,000 domestic breading checkers (DBCs) on strike, MCD says dengue cases on rise in the city. Around 700 Dengue cases have come up in the last 10 days. Several countries have expressed concerns over the rising Dengue cases in Delhi. Many athletes and officials are reportedly reluctant to participate in Commonwealth Games 2010 because of Dengue menace in Delhi. According to the MCD officials, the dengue cases are more than what were reported in past three yeras.   The spread of dengue is taking a serious turn in India. The dengue  fever is rapidly spreading in  northern states of India mainly U.P., Punjab, Dehli, Rajasthan, M.P etc.   Delhi is most affected by Dengu fever. Within last six weeks.

New research on dengue      Scientists in London have identified two genes which they claim increase a person's risk of getting dengue, with nearly 100 million infections occurring annually worldwide. An international team has found changes in the DNA code located in two genes - MICB on chromosome 6 and PLCE1 on chromosome 10 - which increases a person's susceptibility to dengue shock syndrome, a discovery that offers ofering vital clues to how the body responds to the infection.   MICB plays a role in the body's immune system and the team believes that a variant of this gene may affect the activation of natural killer cells or CD8 T-cells, two types of cells that play a key role in combat viral infection. If these cells malfunction, their ability to eliminate the dengue virus is impaired. This hypothesis is consistent with evidence that increased viral loads occur in tissues of patients with severe dengue. Mutations in PLCE1 have previously been linked to nephrotic syndrome, a childhood disease characterized by impairment of the normal barrier and blood filtering functions of kidney cells.  The scientists believe that PLCE1 may also contribute to the normal functioning of the vascular endothelium, the thin layer of cells that lines interior surface of blood vessels, with some variants of PLCE1 predisposing an individual to leakage from the blood vessels.   Lead author Prof Cameron Simmons from the Oxford University Clinical Research Unit, Vietnam , said: "Dengue is a potentially life-threatening disease, it confirms epidemiological evidence that some people are naturally more susceptible to severe forms of the disease than others."         Dengue appears to be spreading fast in the capital with 33 fresh cases being reported as on October 11, 2012, the highest so far for a day this season. In 2011 the capital saw 216 cases of dengue, including eight originating from outside, and three deaths. In 2010, there were 4,108 cases, including 24 from outside, and five deaths while the figures for 2009 were 29 dengue cases and no deaths. In 2008, there were 550 dengue cases and two deaths.

History of Dengue:        Dengue haemorrhagic fever (DHF), a potentially lethal complication,  was first recognized in the 1950s during the dengue epidemics in the  Philippines and Thailand. The global prevalence of dengue has grown  dramatically in recent decades. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. South-east Asia and the Western Pacific are most seriously affected. Before 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995. In 2001 alone, there were more than 609 000 reported cases of dengue in the Americas, of which 15 000 cases were DHF. This is greater than double the number of dengue cases which were recorded in the same region in 1995. In 2001, Brazil reported over 390 000 cases including more than 670 cases of DHF.  An estimated 500 000 cases of DHF require hospitalisation each year, of whom a very large proportion are children. At least 2.5% of cases die.   Dengue and Chikungunya   The same  mosquito-borne virus that can cause an extremely painful, debilitating illness is making a comeback in parts of India and the southwest Indian Ocean. Chikungunya showing symptoms:  include sudden fever followed by a crippling pain in the joints that can cause patients to curl up. There is no vaccine or treatment other than painkillers. Chikungunya is rarely fatal, but it has the potential to temporarily incapacitate. It's potentially catastrophic, not only for health care, but also for workforce implications.