Saturday, 23 July 2016

Revisiting Dengue

Revisiting Dengue

Dr K K Aggarwal

  • Dengue is a mosquito-borne viral infection transmitted by female Aedes aegypti mosquito.
  • Dengue is a notifiable disease. All healthcare providers are required to notify every dengue case to local authorities i.e. District Health Officer/CMO of the district concerned and Municipal Health Officer of the Municipal Corporation/Municipality concerned every week (daily during transmission period) in prescribed format.
  • There are four different serotypes of dengue virus: Den 1, Den 2, Den 3 and Den 4. A person can have dengue 4 times during his lifetime.
  • Infection from one serotype produces lifelong immunity only for that particular serotype.
  • The second dengue infection is usually more severe than the first one.
  • The four dengue-related illnesses are: Undifferentiated fever, dengue fever, dengue hemorrhagic fever, dengue shock syndrome.
  • The main symptoms of dengue are high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain and rash.
  • Retro-orbital pain presenting as pain in the eyes or pressure on eye movement is characteristic of dengue-related fever.
  • Dengue hemorrhagic fever is the more severe form of dengue fever.
  • A patient can be declared as probable case of dengue only on the basis of RDT technique of testing by using NS1 or IgM (not IgG).
  • IgM blood test may take 5 days to become positive.
  • The critical period is during defervescence - transition from the febrile to the afebrile stage - and usually occurs after the 3rd day of illness. Often people insist on a discharge from the hospital when the fever is over or do not want to get admitted once the fever is over.
  • The two dangerous clinical signs are falling systolic (upper) blood pressure and fall in pulse pressure.
  • Platelet transfusion is not required unless platelet count is less than 10,000 or there is presence of spontaneous bleeding.
  • A platelet count of less than one lakh signifies dengue hemorrhagic fever or dengue shock syndrome.
  • Remember the Formula of 20 to identify high risk patients:
o    Rise in pulse by 20
o    Fall in upper blood pressure by more than 20
o    Rise in hematocrit by more than 20 percent
o    Rapid fall in platelets to less than 20,000
o    More than 20 hemorrhagic spots on the arm in one inch after tourniquet test
o    Difference between upper and lower blood pressure is less than 20

Start fluid replacement at 20 ml/kg/hour immediately in such patients, and shift to nearest medical center for observation. 
·         The best way to reduce chances of getting the infection is to eliminate the places where the mosquito breeds. Plastic containers, buckets, drums etc. that hold water in and around the home should be kept covered or discarded properly. Outdoors, water containers like pet and animal water containers, flower planter dishes should be emptied and scrub cleaned at least once a week.

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