Dengue Fever

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Dengue  virus  is  an  arbovirus  transmitted  by  aedes  mosquitoes  (both  Ae.  aegypti  and  Ae.  albopiticus).  Dengue  fever  is  caused  by  four  serologically  distinct,  but  closely  related  Dengue  viruses: dengue virus (DENV) 1, 2, 3, and 4 of the Flaviviridae family. Dengue fever is an emerging  pandemic  that  has  spread  globally  during  the  past  30  years  as  a  result  of  changes  in  human  ecology. Dengue haemorrhagic fever (DHF) is a potentially deadly complication that has become a  leading  cause  of  hospitalization  and  death  among  children  in  Asia  and  Africa.  There  is  good  evidence that sequential infection with the different serotypes of dengue virus increases the risk of  more severe disease that can result in dengue shock syndrome (DSS) and death.  

Infected humans are the main carriers and multipliers of the virus, serving a source of the virus for  uninfected  Aedes  aegypti  mosquitoes  which  maintain  the  urban  dengue  transmission  cycle.  The  virus circulates in the blood of infected human for 2-7 days, at approximately the same time that they  have a fever. A sylvatic transmission cycle has been documented in West Africa where DENV-2 has  been found in monkeys. There is no evidence of person-to-person transmission. 

DENV is frequently transported from one place to another by infected travelers; when susceptible  vectors  are  present  in  these  new  areas,  there  is  the  potential  for  local  transmission  to  be  established. 

Case DefinitionDengue Fever Suspected case: Any person with acute febrile illness of 2-7 days duration with 2 or  more  of  the  following:  headache,  retro-orbital  pain,  myalgia,  arthralgia,  rash,  haemorrhagic  manifestations, leucopenia. 

Dengue  Fever  Confirmed  case:  A  suspected  case  with  laboratory  confirmation  (positive  IgM  antibody, four-fold or greater rise in IgG antibody titres, positive PCR or viral isolation). 

Dengue Haemorrhagic Fever: A probable or confirmed case of dengue with bleeding tendencies  as evidenced by one or more of the following: positive tourniquet test; petechieae, ecchymoses or  purpura; bleeding: mucosa, gastrointestinal tract, injection sites or other; haematemesis or melaena;  and  thrombocytopenia  (100,000  cells  or  less  per  mm3)  and  evidence  of  plasma  leakage  due  to  increased vascular permeability, manifested by one or more of the following: 20% rise in average  haematocrit  for  age  and  sex,  20%  drop  in  haematocrit  following  volume  replacement  therapy  compared to baseline, signs of plasma leakage (pleural effusion, ascites, hypo-proteinaemia). 

Dengue Shock Syndrome: All the above criteria, plus evidence of circulatory failure manifested by  rapid  and  weak  pulse,  and  narrow  pulse  pressure  (≤  20  mm  Hg)  or  hypotension  for  age,  cold,  clammy skin and altered mental status. 

Laboratory Investigations 

  • Reverse Transcriptase–Polymerase Chain Reaction (RT–PCR) 
  • Rapid Tests for Dengue NSI antigen 

Serological methods, such as Enzyme-Linked Immunosorbent Assays (ELISA) for IgM and IgG  anti-dengue antibodies FBP 

Management There is no specific treatment for dengue, but appropriate medical care frequently saves the lives of  patients with dengue haemorrhagic fever. 

Non-Pharmacological Treatment 

  • No specific treatment is available for Dengue fever.  

Pharmacological Treatment:  

A:  paracetamol (PO/IV) 15mg/kg 8hourly for 3days 

A: Maintainance fluid (Ringers lactate, NS) intravenously if one cannot take enough fluid orally  

B: Blood transfusion and clotting factors. 

B: Oxygen and manage hypoglycaemia if present 

Note: 

  • No antibiotics are of proven value.  
  • Children below 12 years require close monitoring for dangerous form.  
  • Steroids should not be used. 
  • Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) such as ibuprofen and aspirin should  be avoided. These anti-inflammatory drugs act by thinning the blood, and in a disease  with risk of hemorrhage, blood thinners may exacerbate the prognosis .

Prevention 

At  present,  the  only  method  of  controlling  or  preventing  dengue  virus  transmission  is  to  combat the vector mosquitoes using environmental management and chemical methods. 

  • Prevent dengue by avoiding mosquito bites by Aedes. aegypti and Aedes. albopictus bite during the day  and night  (using  mosquito  repellant,  bed  nets  and  removing reservoirs). 
  • All four dengue viruses are spread primarily  through the bite of an infected Aedes mosquito. 
  • A dengue vaccine is available for use in some parts of the world. 

Public Health Control Measures 

  • Wear full sleeve clothes and long dresses to cover the limbs 
  • Use mosquito repellents 
  • Use mosquito nets – to protect babies, old people and others, who may rest during the day.  Effectiveness  of  such  nets  can  be  improved  by  treating  them  with  permethrin  (pyrethroid insecticide). Curtains (cloth or bamboo) can also be treated with insecticide and  hung at windows or doorways, to repel or kill mosquitoes