COMMUNICABLECOMMUNICABLE DISEASES DISEASES

DENGUE FEVERDENGUE FEVER

Dr Abu Zar MBBS, MPH (Distinction)Ex-Consultant WHODeputy DHO, Coordinator DHIS Nowshera

DENGUE A MAJOR GLOBAL HEALTH PROBLEMDENGUE A MAJOR GLOBAL HEALTH PROBLEM

Dengue in recent years has become a major Dengue in recent years has become a major international public health concern. Dengue is international public health concern. Dengue is found in tropical and sub-tropical regions found in tropical and sub-tropical regions around the world, predominantly in urban and around the world, predominantly in urban and semi-urban areas.semi-urban areas.

Dengue Haemorrhagic fever (DHF) a potentially Dengue Haemorrhagic fever (DHF) a potentially lethal complication was first recognized in the lethal complication was first recognized in the 1950s during the dengue epidemics in the 1950s during the dengue epidemics in the Philippines and Thailand, but today DHF affects Philippines and Thailand, but today DHF affects most Asian countries and has become a leading most Asian countries and has become a leading cause of hospitalization and death among cause of hospitalization and death among children. children.

The global prevalence of dengue has grown The global prevalence of dengue has grown dramatically in recent decades. The disease is dramatically in recent decades. The disease is now endemic in more than now endemic in more than 100100 countries in countries in AfricaAfrica, the , the AmericasAmericas, the , the Eastern Eastern MediterraneanMediterranean, , South-east AsiaSouth-east Asia and the and the Western PacificWestern Pacific..

South-east Asia and the Western Pacific are most South-east Asia and the Western Pacific are most seriously affected. seriously affected.

Before 1970 only Before 1970 only nine countriesnine countries had had experienced DHF epidemics, a number that had experienced DHF epidemics, a number that had increased more than four-fold by 1995increased more than four-fold by 1995..

Some 2500 million people - Some 2500 million people - two fifthstwo fifths of the of the world's population - are now at risk from dengue. world's population - are now at risk from dengue. WHO currently estimates there may be 50 WHO currently estimates there may be 50 million cases of dengue infection worldwide million cases of dengue infection worldwide every year.every year.

In In 20012001 alone, there were more than alone, there were more than 609000609000 reported cases of dengue in the reported cases of dengue in the Americas, of which Americas, of which 1500015000 cases were cases were Dengue Haemorrhagic Fever. This is Dengue Haemorrhagic Fever. This is greater than greater than doubledouble the number of dengue the number of dengue cases which were recorded in the same cases which were recorded in the same region in region in 19951995..

Not only is the number of cases increasing Not only is the number of cases increasing as the disease is spreading to new areas, as the disease is spreading to new areas, but explosive outbreaks are occurringbut explosive outbreaks are occurring. .

In In 20012001, Brazil reported over 390000 cases , Brazil reported over 390000 cases including more than including more than 670 cases of DHF670 cases of DHF..

Distribution Western Hemisphere

Distribution of dengue, Eastern Hemisphere

An estimated 500,000 cases of DHF require An estimated 500,000 cases of DHF require hospitalization each year, of whom a very large hospitalization each year, of whom a very large proportion are children. At least 2.5% of cases die, proportion are children. At least 2.5% of cases die, although case fatality could be twice as high. although case fatality could be twice as high.

Without proper treatment, DHF case fatality rates Without proper treatment, DHF case fatality rates can exceed 20%. With modern intensive supportive can exceed 20%. With modern intensive supportive therapy, such rates can be reduced to less than therapy, such rates can be reduced to less than 1%.1%.

The spread of dengue is attributed to expanding The spread of dengue is attributed to expanding geographic distribution of the four dengue viruses geographic distribution of the four dengue viruses and of their mosquito vectors, the most important and of their mosquito vectors, the most important of which is the predominantly urban species of which is the predominantly urban species Aedes Aedes aegyptiaegypti..

A rapid rise in urban populations is bringing greater A rapid rise in urban populations is bringing greater numbers of people into contact with this vector, numbers of people into contact with this vector, especially in areas that are favourable for mosquito especially in areas that are favourable for mosquito breeding, e.g. where household water storage is breeding, e.g. where household water storage is common and where solid waste disposal services common and where solid waste disposal services are inadequateare inadequate

In Asia and Amrecas the In Asia and Amrecas the Aedes aegyptiAedes aegypti breeds primarily in man-made containers breeds primarily in man-made containers like:like:

Earthenware jars, Earthenware jars, Metal drums and Metal drums and Concrete cisterns used for domestic water Concrete cisterns used for domestic water

storage.storage. Discarded plastic food containersDiscarded plastic food containers Used automobile tyres and other items that Used automobile tyres and other items that

collect rainwater. collect rainwater.

In Africa it also breeds extensively in In Africa it also breeds extensively in natural habitats such as tree holes and leaf natural habitats such as tree holes and leaf axils.axils.

In recent years, In recent years, Aedes albopictusAedes albopictus, a , a secondary dengue vector in Asia, has secondary dengue vector in Asia, has become established in the United States, become established in the United States, several Latin American and Caribbean several Latin American and Caribbean countries, in parts of Europe.countries, in parts of Europe.

The rapid geographic spread of this The rapid geographic spread of this species has been largely attributed to the species has been largely attributed to the international trade in used tyres.international trade in used tyres.

Dengue SyndromeDengue Syndrome

Dengue fever and dengue hemorrhagic fever Dengue fever and dengue hemorrhagic fever (DHF) are viral diseases transmitted by (DHF) are viral diseases transmitted by AedesAedes mosquitoes, usually mosquitoes, usually Aedes aegyptiAedes aegypti. .

There are four types of this virus (serotypes 1 There are four types of this virus (serotypes 1 to 4) and are closely related to one another.to 4) and are closely related to one another.

Recovery from infection by one provides Recovery from infection by one provides lifelong immunity against that serotype but lifelong immunity against that serotype but confers only partial and transient protection confers only partial and transient protection against subsequent infection by the other against subsequent infection by the other three. three.

There is good evidence that sequential There is good evidence that sequential infection increases the risk of more serious infection increases the risk of more serious disease resulting in DHF.disease resulting in DHF.

Dengue viruses are capable of infecting Dengue viruses are capable of infecting humans and causing disease. These infections humans and causing disease. These infections may be symptomatic, or may lead to:may be symptomatic, or may lead to:

1.1. ““Classical” dengue fever Classical” dengue fever

2.2. Dengue Haemorrhagic fever without shockDengue Haemorrhagic fever without shock

3.3. Dengue Haemorrhagic fever with shockDengue Haemorrhagic fever with shock

DENGUE VIRUS INFECTION

Asymptomatic Symptomatic

Undiffrentiated fever

(viral syndrome)

Dengue fever

(syndrome)

Dengue Haemorrhagic fever

No Shock

Dengue Shock Syndrome (DSS)

(Plasma leakage)Dengue Fever

Dengue Haemorrhagic fever

CLASSICAL DENGUE FEVERCLASSICAL DENGUE FEVER

Reservoir both man and mosquitoReservoir both man and mosquito

The mosquito becomes infective by feeding on The mosquito becomes infective by feeding on the patient from the day before onset to the the patient from the day before onset to the 55thth day of illness. day of illness.

After an extrinsic incubation period of 8-10 After an extrinsic incubation period of 8-10 days the mosquito becomes infective and is days the mosquito becomes infective and is able to transmit infection.able to transmit infection.

The illness is characterized by an incubation The illness is characterized by an incubation period of 3-10 days.period of 3-10 days.

1.1. Onset is sudden with chills and high fever. Onset is sudden with chills and high fever. Temperature rises quickly as high as 104° F Temperature rises quickly as high as 104° F (40° C), with relative bradycardia and (40° C), with relative bradycardia and hypotension.hypotension.

2.2. Reddened eyesReddened eyes

3.3. Intense muscles and joint painsIntense muscles and joint pains

4.4. A flushing or pale pink rash comes over the face and A flushing or pale pink rash comes over the face and then disappears. The glands (lymph nodes) in the then disappears. The glands (lymph nodes) in the neck and groin are often swollen neck and groin are often swollen

5.5. Fever lasts 2-4 days rarely more than 7 days.Fever lasts 2-4 days rarely more than 7 days.

6.6. Recovery is completeRecovery is complete

7.7. Case fatality is very lowCase fatality is very low

Dengue Haemorrhagic Fever Dengue Haemorrhagic Fever

Dengue hemorrhagic fever is a more severe form of the Dengue hemorrhagic fever is a more severe form of the viral illness. viral illness. Caused by more than one dengue viruses. It Caused by more than one dengue viruses. It is due to double infection with dengue virus. The first is due to double infection with dengue virus. The first infection sensitizes the patient and the second appears infection sensitizes the patient and the second appears to produce immunological catastrophe.to produce immunological catastrophe.

Manifestations include:Manifestations include:

Headache, high fever (continuous and lasting 2-7 days) Headache, high fever (continuous and lasting 2-7 days) Rash, andRash, and evidence of hemorrhage in the body evidence of hemorrhage in the body

(Petechiae)(Petechiae) Bleeding in the nose or gums, Bleeding in the nose or gums, Black stools, or easy bruising are all possible signs of Black stools, or easy bruising are all possible signs of

hemorrhage. hemorrhage. This form of dengue fever can be life-threatening or This form of dengue fever can be life-threatening or

even fatal.even fatal.

Skin rash

Symptoms

THERE IS NO DRUG FOR DENGUE. THERE IS NO DRUG FOR DENGUE.

To prevent dengue fever, you must prevent the To prevent dengue fever, you must prevent the breeding of its carrier, the Aedes mosquitoes. breeding of its carrier, the Aedes mosquitoes.

TreatmentTreatment

Because dengue is caused by a virus, there is no Because dengue is caused by a virus, there is no specific medicine or antibiotic to treat it. specific medicine or antibiotic to treat it.

For typical dengue, the treatment is purely For typical dengue, the treatment is purely concerned with relief of the symptoms concerned with relief of the symptoms (symptomatic). (symptomatic).

Rest and fluid intake for adequate hydration is Rest and fluid intake for adequate hydration is important.important.

ImmunizationImmunization

Vaccine development for dengue and DHF is Vaccine development for dengue and DHF is difficult because any of four different viruses difficult because any of four different viruses may cause disease.may cause disease.

Nonetheless, progress is being made in the Nonetheless, progress is being made in the development of vaccines that may protect development of vaccines that may protect against all four dengue viruses. Such products against all four dengue viruses. Such products may become available for public health use may become available for public health use within several years.within several years.

The mosquito flourishes during rainy seasons The mosquito flourishes during rainy seasons but can breed in water-filled flower pots, but can breed in water-filled flower pots, plastic bags, and cans year-round. plastic bags, and cans year-round.

One mosquito bite can inflict the disease.One mosquito bite can inflict the disease.

Under optimal conditions, the egg of an Aedes Under optimal conditions, the egg of an Aedes mosquito can hatch into a larva in less than a mosquito can hatch into a larva in less than a day. day.

The larva then takes about four days to The larva then takes about four days to develop in a pupa, from which an adult develop in a pupa, from which an adult mosquito will emerge after two days.mosquito will emerge after two days.

Three days after the mosquito has bitten a Three days after the mosquito has bitten a person and taken in blood, it will lay eggs, and person and taken in blood, it will lay eggs, and the cycle begins again.the cycle begins again.

Facts about the mosquitoFacts about the mosquito

Only the female aedes mosquito bites as it Only the female aedes mosquito bites as it needs the protein in blood to develop its needs the protein in blood to develop its eggs. eggs.

The mosquito becomes infective The mosquito becomes infective approximately 7 days after it has bitten a approximately 7 days after it has bitten a person carrying the virus.person carrying the virus.

This is the This is the extrinsic incubation periodextrinsic incubation period, , during which time the virus replicates in the during which time the virus replicates in the mosquito and reaches the salivary glands. mosquito and reaches the salivary glands.

Peak biting is at dawn and dusk. Peak biting is at dawn and dusk.

The average lifespan of an Aedes The average lifespan of an Aedes mosquito in Nature is 2 weeks.mosquito in Nature is 2 weeks.

The mosquito can lay eggs about 3 times The mosquito can lay eggs about 3 times in its lifetime, and about 100 eggs are in its lifetime, and about 100 eggs are produced each time. produced each time.

The eggs can lie dormant in dry conditions The eggs can lie dormant in dry conditions for up to about 9 months, after which they for up to about 9 months, after which they can hatch if exposed to favourable can hatch if exposed to favourable conditions, i.e. water and food. conditions, i.e. water and food.

Potential Breeding Sites

PreventionPrevention

The application of appropriate insecticides to The application of appropriate insecticides to larval habitats.larval habitats.

During outbreaks, emergency control During outbreaks, emergency control measures may also include the application of measures may also include the application of insecticides as:insecticides as:

space sprays to kill adult mosquitoes using space sprays to kill adult mosquitoes using portable or truck-mounted machines or even portable or truck-mounted machines or even aircraft.aircraft.

However, the killing effect is only transient, However, the killing effect is only transient, variable in its effectiveness because the variable in its effectiveness because the aerosol droplets may not penetrate indoors to aerosol droplets may not penetrate indoors to microhabitats where adult mosquitoes are microhabitats where adult mosquitoes are hiding.hiding.

Dengue Prevention ChecklistDengue Prevention Checklist

To prevent the spread of dengue fever, we To prevent the spread of dengue fever, we must first prevent the breeding of its must first prevent the breeding of its vector, the Aedes mosquitoes. vector, the Aedes mosquitoes.

The Aedes mosquito is easily identifiable The Aedes mosquito is easily identifiable by its distinctive black and white stripes by its distinctive black and white stripes on their body. It prefers to breed in clean, on their body. It prefers to breed in clean, stagnant water easily found in our homes. stagnant water easily found in our homes.

We can get rid of the Aedes mosquito by We can get rid of the Aedes mosquito by frequently checking and removing frequently checking and removing stagnant water in our premises.stagnant water in our premises.

CHECKLISTCHECKLIST

At all timesAt all times

Turn pails and watering cans over and Turn pails and watering cans over and

store them under shelter.store them under shelter.

Remove water in plant pot plates. Remove water in plant pot plates. Clean and scrub the plate thoroughly Clean and scrub the plate thoroughly to remove mosquito eggs. Avoid the to remove mosquito eggs. Avoid the use of plant pot plates, if possible. use of plant pot plates, if possible.

Loosen soil from potted plants to prevent Loosen soil from potted plants to prevent the accumulation of stagnant water on the the accumulation of stagnant water on the surface of the hardened soil.surface of the hardened soil.

Do not block the flow of water in scupper Do not block the flow of water in scupper drains.drains.

Cover rarely used gully traps. Cover rarely used gully traps. Replace the gully trap with non-Replace the gully trap with non-perforated ones and install anti-perforated ones and install anti-mosquito valves.mosquito valves.

No tray or receptacles should be placed beneath and No tray or receptacles should be placed beneath and or/ on top of any air-conditioning unit so as not to or/ on top of any air-conditioning unit so as not to create a condition favourable for mosquito breeding. create a condition favourable for mosquito breeding. 

Every other dayEvery other day

Change water in flower vases. Clean and scrub the Change water in flower vases. Clean and scrub the inner sides of vases. Wash roots of flowers and plants inner sides of vases. Wash roots of flowers and plants thoroughly as mosquito eggs can stick to them easily.thoroughly as mosquito eggs can stick to them easily.

Once a weekOnce a week

Clear fallen leaves and stagnant water in your Clear fallen leaves and stagnant water in your scupper drains and garden. scupper drains and garden.

These leaves could collect water or cause These leaves could collect water or cause blockages to the drains, thus resulting in the blockages to the drains, thus resulting in the build-up of stagnant water. build-up of stagnant water.

Clear any stagnant water in your air cooler unit.Clear any stagnant water in your air cooler unit.

Once a monthOnce a month

Add prescribed amounts of sand granular Add prescribed amounts of sand granular insecticide into vases, gully traps and roof insecticide into vases, gully traps and roof gutters, even if they are dry.gutters, even if they are dry.

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