COMMUNICABLE DISEASES

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COMMUNICABLE DISEASES

• DENGUE FEVER
• Dr Abu Zar Taizai

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• DENGUE A MAJOR GLOBAL HEALTH PROBLEM
• Dengue in recent years has become a major
  international public health concern. Dengue is
  found in tropical and sub-tropical regions around
  the world, predominantly in urban and semi-urban
  areas.
• Dengue Haemorrhagic fever (DHF) a potentially
  lethal complication was first recognized in the
  1950s during the dengue epidemics in the
  Philippines and Thailand, but today DHF affects
  most Asian countries and has become a leading
  cause of hospitalization and death among
  children.

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

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• In 2001 alone, there were more than 609000
  reported cases of dengue in the Americas, of
  which 15000 cases were Dengue Haemorrhagic Fever.
  This is greater than double the number of dengue
  cases which were recorded in the same region in
  1995.
• Not only is the number of cases increasing as the
  disease is spreading to new areas, but explosive
  outbreaks are occurring.
• In 2001, Brazil reported over 390000 cases
  including more than 670 cases of DHF.

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Distribution Western Hemisphere
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Distribution of dengue, Eastern Hemisphere
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• An estimated 500,000 cases of DHF require
  hospitalization each year, of whom a very large
  proportion are children. At least 2.5 of cases
  die, although case fatality could be twice as
  high.
• Without proper treatment, DHF case fatality rates
  can exceed 20. With modern intensive supportive
  therapy, such rates can be reduced to less than
  1.
• The spread of dengue is attributed to expanding
  geographic distribution of the four dengue
  viruses and of their mosquito vectors, the most
  important of which is the predominantly urban
  species Aedes aegypti.
• A rapid rise in urban populations is bringing
  greater numbers of people into contact with this
  vector, especially in areas that are favourable
  for mosquito breeding, e.g. where household water
  storage is common and where solid waste disposal
  services are inadequate

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• In Asia and Amrecas the Aedes aegypti breeds
  primarily in man-made containers like
• Earthenware jars,
• Metal drums and
• Concrete cisterns used for domestic water
  storage.
• Discarded plastic food containers
• Used automobile tires and other items that
  collect rainwater.
• In Africa it also breeds extensively in natural
  habitats such as tree holes and leaf axils.

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

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• Dengue Syndrome
• Dengue fever and dengue hemorrhagic fever (DHF)
  are viral diseases transmitted by Aedes
  mosquitoes, usually Aedes aegypti.
• There are four types of this virus (serotypes 1
  to 4) and are closely related to one another.
• Recovery from infection by one provides lifelong
  immunity against that serotype but confers only
  partial and transient protection against
  subsequent infection by the other three.
• There is good evidence that sequential infection
  increases the risk of more serious disease
  resulting in DHF.

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• Dengue viruses are capable of infecting humans
  and causing disease. These infections may be
  symptomatic, or may lead to
• Classical dengue fever
• Dengue Haemorrhagic fever without shock
• Dengue Haemorrhagic fever with shock

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DENGUE VIRUS INFECTION
Asymptomatic
Symptomatic
Dengue Haemorrhagic fever
Undiffrentiated fever (viral syndrome)
Dengue fever (syndrome)
(Plasma leakage)
Dengue Shock Syndrome (DSS)
No Shock
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• CLASSICAL DENGUE FEVER
• Reservoir both man and mosquito
• The mosquito becomes infective by feeding on the
  patient from the day before onset to the 5th day
  of illness.
• After an extrinsic incubation period of 8-10
  days the mosquito becomes infective and is able
  to transmit infection.
• The illness is characterized by an incubation
  period of 3-10 days.
• Onset is sudden with chills and high fever.
  Temperature rises quickly as high as 104 F (40
  C), with relative bradycardia and hypotension.

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• Reddened eyes
• Intense muscles and joint pains
• A flushing or pale pink rash comes over the face
  and then disappears. The glands (lymph nodes) in
  the neck and groin are often swollen
• Fever lasts 2-4 days rarely more than 7 days.
• Recovery is complete
• Case fatality is very low

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• Dengue Haemorrhagic Fever
• Dengue hemorrhagic fever is a more severe form
  of the viral illness. Caused by more than one
  dengue viruses. It is due to double infection
  with dengue virus. The first infection sensitizes
  the patient and the second appears to produce
  immunological catastrophe.
• Manifestations include
• Headache, high fever (continuous and lasting 2-7
  days)
• Rash, and evidence of hemorrhage in the body
  (Petechiae)
• Bleeding in the nose or gums,
• Black stools, or easy bruising are all possible
  signs of hemorrhage.
• This form of dengue fever can be life-threatening
  or even fatal.

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Symptoms
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• THERE IS NO DRUG FOR DENGUE.
• To prevent dengue fever, you must prevent the
  breeding of its carrier, the Aedes mosquitoes.

Treatment Because dengue is caused by a virus,
there is no specific medicine or antibiotic to
treat it. For typical dengue, the treatment is
purely concerned with relief of the symptoms
(symptomatic). Rest and fluid intake for
adequate hydration is important.
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• Immunization
• Vaccine development for dengue and DHF is
  difficult because any of four different viruses
  may cause disease.
• Nonetheless, progress is being made in the
  development of vaccines that may protect against
  all four dengue viruses. Such products may become
  available for public health use within several
  years.

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• The mosquito flourishes during rainy seasons but
  can breed in water-filled flower pots, plastic
  bags, and cans year-round.
• One mosquito bite can inflict the disease.
• Under optimal conditions, the egg of an Aedes
  mosquito can hatch into a larva in less than a
  day.
• The larva then takes about four days to develop
  in a pupa, from which an adult mosquito will
  emerge after two days.
• Three days after the mosquito has bitten a person
  and taken in blood, it will lay eggs, and the
  cycle begins again.

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• Facts about the mosquito
• Only the female aedes mosquito bites as it needs
  the protein in blood to develop its eggs.
• The mosquito becomes infective approximately 7
  days after it has bitten a person carrying the
  virus.
• This is the extrinsic incubation period, during
  which time the virus replicates in the mosquito
  and reaches the salivary glands.

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• Peak biting is at dawn and dusk.
• The average lifespan of an Aedes mosquito in
  Nature is 2 weeks.
• The mosquito can lay eggs about 3 times in its
  lifetime, and about 100 eggs are produced each
  time.
• The eggs can lie dormant in dry conditions for up
  to about 9 months, after which they can hatch if
  exposed to favourable conditions, i.e. water and
  food.

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Potential Breeding Sites
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• Prevention
• The application of appropriate insecticides to
  larval habitats.
• 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 hiding.

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• Dengue Prevention Checklist
• To prevent the spread of dengue fever, we must
  first prevent the breeding of its vector, the
  Aedes mosquitoes.
• The Aedes mosquito is easily identifiable by its
  distinctive black and white stripes on their
  body. It prefers to breed in clean, stagnant
  water easily found in our homes.
• We can get rid of the Aedes mosquito by
  frequently checking and removing stagnant water
  in our premises.

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• CHECKLIST
• At all times
• Turn pails and watering cans over and store them
  under shelter.

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

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• Loosen soil from potted plants to prevent the
  accumulation of stagnant water on the surface of
  the hardened soil.
• Do not block the flow of water in scupper drains.

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

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• No tray or receptacles should be placed beneath
  and or/ on top of any air-conditioning unit so as
  not to create a condition favourable for mosquito
  breeding. 
• Every other day
• Change water in flower vases. Clean and scrub
  the inner sides of vases. Wash roots of flowers
  and plants thoroughly as mosquito eggs can stick
  to them easily.

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• Once a week
• Clear fallen leaves and stagnant water in your
  scupper drains and garden.
• These leaves could collect water or cause
  blockages to the drains, thus resulting in the
  build-up of stagnant water.
• Clear any stagnant water in your air cooler unit.
• Once a month
• Add prescribed amounts of sand granular
  insecticide into vases, gully traps and roof
  gutters, even if they are dry.

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• Thanks

• DENGUE FEVER
• Dr Abu Zar Taizai