Dengue in india

Impact of Dengue

During the 19th century, dengue was considered a sporadic disease that caused epidemics at long intervals, a reflection of the slow pace of transport and limited travel at that time. Today, dengue ranks as the most important mosquito-borne viral disease in the world. In the last 50 years, incidence has increased 30-fold. An estimated 2.5 billion people live in over 100 endemic countries and areas where dengue viruses can be transmitted. Up to 50 million infections occur annually with 500 000 cases of dengue haemorrhagic fever and 22,000 deaths mainly among children. Prior to 1970, only 9 countries had experienced cases of dengue haemorrhagic fever (DHF); since then the number has increased more than 4-fold and continues to rise.

Dengue fever
The clinical features of DF frequently depend on the age of the patient. Infants
and young children may have an undifferentiated febrile disease, often with a
maculopapular rash. Older children and adults may have either a mild febrile
syndrome or the classic incapacitating disease with high fever of abrupt onset,
sometimes with 2 peaks (saddle-backed), severe headache, pain behind the
eyes, muscle and bone or joint pains, nausea and vomiting, and rash. Skin
haemorrhages (petechiae) are not uncommon. Leukopenia is usually seen and
thrombocytopenia may be observed. Recovery may be associated with pro-
longed fatigue and depression, especially in adults.

Case definition for dengue haemorrhagic fever
The following must all be present:

Fever, or history of acute fever, lasting 2–7 days, occasionally biphasic.
Haemorrhagic tendencies, evidenced by at least one of the following:
— a positive tourniquet test1
— petechiae, ecchymoses or purpura
— bleeding from the mucosa, gastrointestinal tract, injection sites or other
locations
— haematemesis or melaena.
Thrombocytopenia (100 000 cells per mm3 or less).2
Evidence of plasma leakage due to increased vascular permeability, mani-
fested by at least one of the following:
— a rise in the haematocrit equal to or greater than 20% above average for
age, sex and population;


Indications for hospitalization
Hospitalization for bolus intravenous fluid therapy may be necessary where
significant dehydration (Ͼ10% of normal body weight) has occurred and rapid
volume expansion is needed. Signs of signficant dehydration include:

1. Tachychardia
2. Increased capillary refill time (Ͼ2 s)
3. Cool, mottled or pale skin
4. Diminished peripheral pulses
5. Changes in mental status
6. Oliguria
7. Sudden rise in haematocrit or continuously elevated haematocrit despite
8. administration of fluids
9. Narrowing of pulse pressure (Ͻ20 mmHg (2.7 kPa) )
10. Hypotension (a late finding representing uncorrected shock).

Essential laboratory tests
In assessing a patient’s condition, the following tests are recommended:

1. Haematocrit
2. Serum electrolytes and blood gas studies
3. Platelet count, prothrombin time, partial thromboplastin time and thrombin time
4. Liver function tests—serum aspartate aminotransferase, serum alanine ami-
5. notransferase and serum proteins.

Criteria for discharging inpatients
The following criteria should be met before patients recovering from DHF/
DSS are discharged:

• Absence of fever for at least 24 hours without the use of antifever therapy (cryotherapy or antipyretics)
• Return of appetite
• Visible clinical improvement
• Good urine output
• Stable haematocrit
• Passing of at least 2 days after recovery from shock
• No respiratory distress from pleural effusion or ascites
• Platelet count of more than 50 000 per mm3.

http://www.who.int/csr/resources/publications/dengue/Denguepublication/en/


Frequently Asked Questions

Q. What is dengue?
A. Dengue (pronounced den' gee) is a disease caused by any one of four closely related dengue viruses (DENV 1, DENV 2, DENV 3, or DENV 4). The viruses are transmitted to humans by the bite of an infected mosquito. In the Western Hemisphere, the Aedes aegypti mosquito is the most important transmitter or vector of dengue viruses, although a 2001 outbreak in Hawaii was transmitted by Aedes albopictus. It is estimated that there are over 100 million cases of dengue worldwide each year.

Q.What is dengue hemorrhagic fever (DHF)?
A.DHF is a more severe form of dengue infection. It can be fatal if unrecognized and not properly treated in a timely manner. DHF is caused by infection with the same viruses that cause dengue fever. With good medical management, mortality due to DHF can be less than 1%.

Q.How are dengue and dengue hemorrhagic fever (DHF) spread?
A. Dengue is transmitted to people by the bite of an Aedes mosquito that is infected with a dengue virus. The mosquito becomes infected with dengue virus when it bites a person who has dengue virus in their blood. The person can either have symptoms of dengue fever or DHF, or they may have no symptoms. After about one week, the mosquito can then transmit the virus while biting a healthy person. Dengue cannot be spread directly from person to person.

Q.What are the symptoms of the disease?
A. The principal symptoms of dengue fever are high fever, severe headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash, and mild bleeding (e.g., nose or gums bleed, easy bruising). Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.

Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms consistent with dengue fever. When the fever declines, symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing, may develop. This marks the beginning of a 24- to 48-hour period when the smallest blood vessels (capillaries) become excessively permeable (“leaky”), allowing the fluid component to escape from the blood vessels into the peritoneum (causing ascites) and pleural cavity (leading to pleural effusions). This may lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected. In addition, the patient with DHF has a low platelet count and hemorrhagic manifestations, tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding.

Q.What is the treatment for dengue?
A. There is no specific medication for treatment of a dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with acetaminophen and avoid those containing aspirin. They should also rest, drink plenty of fluids, and consult a physician. If they feel worse (e.g., develop vomiting and severe abdominal pain) in the first 24 hours after the fever declines, they should go immediately to the hospital for evaluation.

Q.Is there an effective treatment for dengue hemorrhagic fever (DHF)?
A. As with dengue fever, there is no specific medication for DHF. It can however be effectively treated by fluid replacement therapy if an early clinical diagnosis is made. DHF management frequently requires hospitalization. Physicians who suspect that a patient has DHF may want to consult the Dengue Branch at CDC, for more information.

Q. Where can outbreaks of dengue occur?
A.Outbreaks of dengue occur primarily in areas where Ae. aegypti (sometimes also Ae. albopictus) mosquitoes live. This includes most tropical urban areas of the world. Dengue viruses may be introduced into areas by travelers who become infected while visiting other areas of the tropics where dengue commonly exists.

Q.What can be done to reduce the risk of acquiring dengue?
A.There is no vaccine for preventing dengue. The best preventive measure for residents living in areas infested with Ae. aegypti is to eliminate the places where the mosquito lays her eggs, primarily artificial containers that hold water.

Items that collect rainwater or to store water (for example, plastic containers, 55-gallon drums, buckets, or used automobile tires) should be covered or properly discarded. Pet and animal watering containers and vases with fresh flowers should be emptied and cleaned (to remove eggs) at least once a week. This will eliminate the mosquito eggs and larvae and reduce the number of mosquitoes present in these areas.

Using air conditioning or window and door screens reduces the risk of mosquitoes coming indoors. Proper application of mosquito repellents containing 20% to 30% DEET as the active ingredient on exposed skin and clothing decreases the risk of being bitten by mosquitoes. The risk of dengue infection for international travelers appears to be small. There is increased risk if an epidemic is in progress or visitors are in housing without air conditioning or screened windows and doors.

Q.How can we prevent epidemics of dengue hemorrhagic fever (DHF)?
A.The emphasis for dengue prevention is on sustainable, community-based, integrated mosquito control, with limited reliance on insecticides (chemical larvicides, and adulticides). Preventing epidemic disease requires a coordinated community effort to increase awareness about dengue fever/DHF, how to recognize it, and how to control the mosquito that transmits it. Residents are responsible for keeping their yards and patios free of standing water where mosquitoes can be produced.
http://www.cdc.gov/dengue/fAQFacts/index.html
http://www.cdc.gov/dengue/prevention/index.html
http://www.healthmap.org/dengue/index.php

Methods for environmental management
Environmental management methods to control Ae. aegypti and Ae. albopictus
and reduce human–vector contact include the improvement of water supply
and storage, solid waste management and the modification of man-made larval
habitats. Table 5.2 summarizes the primary methods of environmental manip-
ulation used to control Aedes larval habitats.
Environmental management should focus on the destruction, alteration,
disposal or recycling of containers and natural larval habitats that produce the
greatest number of adult Aedes mosquitos in each community. These pro-
grammes should be conducted concurrently with health education programmes
and communications that encourage community participation in the planning,
execution and evaluation of container-management programmes (e.g. regular
household sanitation or clean-up campaigns).


Improvement of water supply and storage
One method for controlling urban Aedes vectors, particularly Ae. aegypti, is to
improve domestic water supplies. The mere delivery of potable water to neigh
bourhoods or individual homes is not, however, sufficient to reduce the use of
the water storage containers that play a dominant role in Ae. aegypti breeding
in many urban areas. For example, after piped water had been supplied to
households in one municipality in Thailand, approximately eight water storage
jars were still kept by each household. Similar situations have been reported
elsewhere in Asia and the Caribbean. Households typically continue to store
water because water supplies are not reliable. With such water storage comes
the concomitant problem of Ae. aegypti breeding and the increased risk of
dengue infection. Therefore, potable water must be delivered in sufficient
quantity, quality and consistency to reduce the use of water storage containers
that serve as larval habitats, such as drums, overhead tanks, and jars. Water
piped to households is preferable to wells, communal standpipes, rooftop
catchments and other delivery systems. If storage tanks, drums and jars are
required for water storage, they should be covered with tight lids or screens.
Many people fail to cover water containers because lids and screens are not
designed in such a way that they will seal containers while nevertheless enabling
users to withdraw water easily. Water storage systems, however, can be de-
signed to prevent Ae. aegypti oviposition or adult emergence. In Sarawak,
Malaysia, for example, mosquito-proof rainwater collection and storage con-
tainers made of high-density polyethylene have fibreglass screens in the lids that
allow rainwater to enter but prevent adult mosquitos from emerging. Covered
containers should be routinely inspected because even the best-designed lids
and screens can tear or deteriorate in harsh climates and with age.
Solid waste management
Vector control efforts should encourage effective and environmentally sound
waste management by promoting the basic rule of “reduce, reuse, recycle”. In
some parts of Africa, plastic containers that may serve as potential larval
habitats are effectively recycled. Used tyres are another form of solid waste that
is of critical importance to urban Aedes control; they should be recycled or
disposed of by proper incineration in waste transformation facilities (e.g. incin-
erators, energy-production plants, lime kilns). If cut into halves, shredded, or
chipped, tyres can be mixed with other wastes and buried in landfills, as local
sanitary regulations allow. Whole tyres should be buried in a separate area of a
landfill, to avoid their rising upwards under compaction and disrupting soil
cover.
Modification of man-made larval habitats
Common-sense approaches should be employed to reduce the potential for Ae.
aegypti mosquitos to breed in and around human habitats. For example, fences
and fence posts made from hollow stems, such as bamboo, should be cut to the
node; tyres and containers stored outside should be covered or placed in a shed,
and buckets and other small containers should be inverted if stored outdoors.
Ant traps used to protect food storage cabinets can be filled with oil or salty
water instead of fresh water; condensate-collection pans under refrigerators
and air-conditioning units should be drained and cleaned regularly. Floor
drains should be cleaned and kept covered. Roof gutters, outdoor sinks, laun-
dry basins and similar items that can retain water and serve as larval habitats
should be drained and kept free of debris. Ornamental pools and fountains can
be either chlorinated or populated with larvivorous fish. Where possible, hous-
ing should be designed or modified to reduce opportunities for mosquitos to
enter, i.e. without open eaves and with screened doors and windows. These
measures and others will help reduce or prevent the breeding of vector mosqui-
tos near humans, and thereby diminish the risk of dengue viral disease.
Chemical control
Chemicals have been used to control Ae. aegypti since the turn of the century.
In the first campaigns against yellow fever in Cuba and Panama, in conjunction
with widespread clean-up campaigns, Aedes larval habitats were treated with oil
and houses were dusted with pyrethrins. When the insecticidal properties of
DDT were discovered in the 1940s, this compound became the principal
method for Ae. aegypti eradication programmes in the Americas. When resist-
ance to DDT emerged in the early 1960s, organophosphate insecticides, in-
cluding fenthion, malathion, fenitrothion and temephos, were used for Ae.
aegypti control. Current methods for applying insecticides include larvicide
application, perifocal treatment and space spraying.
Application methods
Larvicidal or “focal” control of Ae. aegypti is usually limited to containers
maintained for domestic use that cannot be eliminated. Three larvicides can be
used to treat containers that hold drinking-water: 1% temephos sand granules,
the insect growth regulator methoprene in the form of briquettes, and BTI
(Bacillus thuringiensis H-14), which is considered below in the section on bio-
logical control. All these larvicides have extremely low mammalian toxicity, and
properly treated drinking-water is safe for human consumption.
Perifocal treatment involves the use of hand or power sprayers to apply
wettable powder or emulsifiable-concentrate formulations of insecticide as a
spray to larval habitats and peripheral areas. This will destroy existing and
subsequent larval infestations in containers of non-potable water, as well as kill
the adult mosquitos that frequent these sites. This method can be used to treat
containers that are preferred by Ae. aegypti, whether or not they hold water.
The internal and external walls of containers are sprayed until they are covered
by a film of insecticide; spraying is also extended to cover any wall within 60 cm
of the container. The surface of non-potable water in containers is also treated.


Selected insecticides and dosages for cold-spray control of Aedes aegypti a Dosage (grams of active ingredient per ha)

Organophosphates
Malathion
Fenitrothion
Naled
Pirimiphos-methyl
Pyrethroids
Deltamethrin
Resmethrin
Bioresmethrin
Permethrin
Cypermethrin
Lamda-cyhalothrin