Dengue fever

Dengue 

Aedes aegypti

" Dengue is a mosquito-borne viral infection in human beings." "Break bone fever This disease had also been known as break-bone fever. “Dengue” is a Spanish word meaning careful. It might have been used because a person suffering from severe pain in bones and joints moves carefully It is derived from a Swahili word “Dinga ” which means “evil spirit”, Swahili is spoken in many East and North African countries. 

Rapidly spreading disease

World wide spread In a few years' time, it has become the most rapidly spreading international public health problem, particularly in urban and semi-urban areas of tropical and sub-tropical regions of the world. More than 50 million people are in contact with the disease each year.

 History  of dengue

The first reported epidemics of dengue fever occurred in 1779-1780 in Asia, Africa, and North America almost simultaneously. At that time, dengue virus and vector mosquitoes had a worldwide distribution in the tropics and subtropics. 

Vector of dengue virus

Aedes aegypti was identified as a vector of dengue virus in 1905. A global pandemic of dengue began in Southeast Asia after World War II. It has intensified during the last two decades in many countries. Sri Lanka, India, and Maldive Islands had their first major DHF epidemics in 1980s. 

Phases of dengue

Febrile Phase of dengue

 It usually lasts for 2-7 days from the beginning of the illness. In this phase temperature of the patient may rise above 102°F, with generalized pain and headache. So patients may have sore throat. It is difficult to distinguish dengue from non-dengue in early febrile phase. A positive tourniquet test increases the probability of dengue. Rash appears in 50-80 % patients, initially as flushed skin but after 4-7 days as measles like rash. 
When skin is pressed capillaries are broken, tiny red spots .Mild bleeding may occur from nose and gums. In some patients gastrointestinal bleeding also occurs. The liver often enlarges after a few days. The number of platelets and white blood cells progressively decreases. After about 2- 3 days the symptoms of the disease.

 Critical Phase of dengue

 It usually lasts for 1 -2 days. The temperature drops to normal on day 3-7 of illness. The permeability of capillaries increases. Fluid/plasma leaks for 24-48 hours and accumulates in the chest and abdominal cavities. Platelet level further decreases. It increases the leakage of plasma from the blood capillaries. This leads to decrease of fluid in circulation, hence decrease of blood supply to vital organs (liver, kidney, heart, brain etc.). It may cause organ dysfunction, severe bleeding, low heart rate and low blood pressure. 

 Dengue hemorrhagic fever (DHF) and dengue shock syndrome

 (DSS) occur in less than 5 % of cases. Dengue hemorrhagic fever is characterized by high fever, headache, small purplish spots on skin due to leakage of blood from capillaries, abdominal pain, vomiting with blood due to bleeding in stomach. People with low immunity or with secondary infection are at greater risk of developing DHF. A small proportion of DHF cases may lead to dengue shock syndrome. DSS can damage body organs like heart and kidney due to low blood supply. 

Recovery Phase  of dengue

Recovery phase lasts for 2-3 days. During this phase reabsorption of leaked fluid into the blood stream takes place. Appetite returns, bleeding, nausea and vomiting decrease, large urine output occurs; plasma level is restored, white blood cells and platelets start increasing. Fever and other symptoms rarely last for more than seven days. 

Diagnosis of dengue

 Early diagnosis is necessary for the accurate treatment and proper management of the disease. Nearest physician must be contacted for his advice. Quacks and self- medication should be strictly avoided.Clinical tests are carried out on the advice of the physician for diagnosis of dengue fever. It is a broad screening test for many diseases. Automated analyzer gives a profile of number of different types of WBCs (white blood cells), RBCs (red blood 4cells) and platelets per unit volume. 
Low WBC and platelet count may indicate dengue. Type of cells Normal Range RED Blood Cells (RBCs) 3900000-5500000/pi White Blood Cells (WBCs) 4000-10000/pi Platelets 150000-450000/pi Tourniquet Test. For this test the cuff of the blood pressure instrument is applied around the arm, inflated to a pressure about 105 mm Hg (mm of mercury) for five minutes and then removed. Small round flat dark-red spots (petechiae) may appear on the skin. 
These are formed by bleeding into the skin. Detection of Antibodies Certain antibodies produced the human body in response to viral infection e.g., Ig G and Ig M. These antibodies can be detected around the fifth day of dengue onset. Treatment Rest Complete rest is advised by the physician. It is the most effective method for controlling any kind of disease.
 Activity or anxiety uses body's energy. Sponging In the case of high fever, body temperature should be kept below 102F. Doctors advise that it may be lowered by sponging with moderately cold water. Rehydration Patient should increase fluid intake through fruit juices and ORS . It is very important to replace loss of fluid, sugar and electrolytes. Adequate fluid intake reduces the chance of hospitalizations.

 Hospitalization of Dengue patients 

Dengue patients in hospital

 

All patients need not to be hospitalized. They may be sent home by the physician after early diagnosis of mild symptoms. Most of the dengue patients can be treated as “out patients” and advised to immediately rush to hospital in the case of emergency. 
 Isolation  of dengue patients
Complete isolation of the patient is not required, however, use of mosquito net is mandatory so that a mosquito may not get virus from the patient. Hospital environment should be insect free. Travelling The patient should not travel to long distance to avoid spread of disease to other areas.

 Platelet Transfusion of dengue patient

Platelet transfusion is not required in most of the cases. A qualified doctor regularly monitors the platelet count and decides the time for transfusion. Platelet transfusion from a suitable donor should be carried out under his supervision in a hospital. Proper screening and cross matching of donor and recipient is necessary. 
Concentrated form of platelets separated from single donor is called mega unit of platelets. These separators quickly isolate only the platelets and simultaneously return rest of the blood back to the donor. Control Presently there is no specific vaccine available for dengue fever. Therefore, the only choice left is to control the vector involved in the transmission of dengue virus. 
Control of mosquito also helps to control other diseases like malaria and yellow fever. 

 Protection  from dengue

 ♣ Bed nets should be used to protect the people from mosquito bite. Aedes mosquito mostly bites during the day and Anopheles at night. Bed nets are more effective when they are treated with an insecticide or insect repellent. 
 ♣ Mosquito repellent in the form of body lotions may help avoid mosquito bite. Aerosol insecticides, vaporising mats and mosquito coils should be used in rooms. Curtains may also be sprayed with mosquito repellents. 
♣ Minimise area of exposed skin by wearing full sleeve shirts and long pants. Wearing socks and closed shoes further reduces the risk. Mosquito repellent can also be applied to clothes for further protection. Avoid wearing dark and tight clothes, because mosquito attacks more on dark colours and can easily bite through tight clothes. 
♣Screening of Houses, Offices etc: Screening of windows and doors with fine wire net bans entry of mosquitoes. Dengue patient should always be kept in screened room to avoid viral spread from the patient. 
♣ People should reschedule the pattern of daily activities of life. We should avoid going outside during the peak hours of mosquito activity. Moreover, we should avoid visiting areas of epidemics. 
 ♣ Vaccines are weak or killed germs, which when introduced in the body induce immunity against the healthy germs. Dengue vaccine is not yet available. A quadrivalent vaccine for all four dengue serotypes is still awaited. 
♣ Aedes breed mainly in stagnant clean water bodies such as earthenware jars and domestic water storage tanks. But discarded plastic food containers, toys, old tyres, tree holes and leaf axils that can collect rain water, gutters and drains are also potential breeding sites. Following measures should be taken to destroy these breeding sites.
 ♣ Cover any water container. Remove any bottle, plastic bag, pot, old pan, tin and old tyre. 
♣Remove any water standing in lawn, flower beds and pots.Change water in vases/bowls, flower pots and plates on alternate days.Close and dry all swimming pools and fountains during breeding season of mosquito. 
 ♣Drain out or regularly change water from room cooler. Also drain out water coming out from air conditioners. 
 ♣Change water regularly in fish aquarium.Drain any stagnant rain water, fill these sites with sand and soil. 
 ♣Remove trash from streams and drains. 
♣Clean toilet and gully trap every day. 
 ♣Turn over all water storage buckets and small tubs.Clear any blockage in roof drain pipes regularly. 
♣ Remove water from leaf axils and tree holes or add some insecticides. 
♣Adult mosquito can be killed by the use of insecticides. Insecticides should be used carefully. 
 ♣ Avoid any direct inhalation of spray or smoke. Insecticides should be sprayed inside buildings, particularly on walls, behind the curtains, under the bed and sofa. 
 ♣Doors should be closed for some time after the spray. Fogging should be used to kill the mosquitoes in open places 
♣Unwise use of insecticides may cause health hazards and may produce resistant strains of mosquitoes. 
 ♣Different types of electric mosquito killers are used. These include electric vaporizer, electric mosquito trap, electric mosquito catcher, mosquito mat etc. 
♣ Biological control should be adopted to avoid the harmful effects of chemicals. In biological control living organisms are used to kill the mosquitoes. 
♣Spiders, lizards and dragon flies are the natural predators of mosquito. Introduction of these organisms can markedly reduce the number of mosquitoes.
 ♣ Horticulture Discipline: Regularly cut the grass and weeds where mosquitoes may hide. 
♣ Chemical control: Application of larvicidal chemicals to the breeding sites reduces the mosquito population. Spray of kerosene oil on water blocks the air tube/siphon of mosquito larvae and kills them, but these chemicals also destroy useful animal and plant life in water bodies. 
 ♣ Living organisms can be used to destroy the mosquito larvae. Many fishes and copepods predate upon mosquito larvae. A bacterium produces toxins which kill mosquito larvae. It can also be used for biological control. 
 ♣We can destroy the eggs by using ovitraps. Ovitraps are black plastic water containers with paddles that are in contact with the surface of water. These ovitraps attract the female mosquito to lay eggs. In these ovitraps either the female is trapped or eggs are killed by chemicals mixed with water in ovitrap. Ovitraps should be used with care.
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