causeative agent dengue virus
family – flavi virus
agent responsible for spread – AEDES AGYPTI mosquito.
dengue is the most common arthropod -borne viral infection in humans in the worldd.
dengue virus is the most common typ of arbovirus in indai. there are 5 sero-types of dengue virus in nature (DEN 1 TO DEN-5).
cycle of transmission in mosquito
2 weeks after a mosquito bites a patient of dengue, the mosquito itself becomes infective. such an infective mosquito becomes a carrier of dengue and an spread dengue to other humans throughout it’s life. intersting that a aedes mosquito can pass the dengue virus to it;s offspring viral its ovaries.
apart from aedes mosquito and humans, no other animal are not invovled in the cycle o dengue virus.
the aedes aegypti mosquito are day time mosquitos. meaning, they bite during day time.
these mosquitoes are breed in stagnant water. hence collections of water around our house sucha s water containers, water based cooers and tire dumps are some of the ost common locations where these mosquitoes can grow and breed.
4-10 days after bite.
after a person in bit by an aedes mosquito, the symptoms start to appear 4-10 days after the bite. before that, the person may be completely asymptomatic.
clinical symptoms of dengue
just like any other disease, a patient of dengue may even by asymtpomatic and may not show any symtoms throughand may even recover on its’s own.
but many patients of dengue do show symptoms. symptoms of dengue can be divided into 3 phases- 1. febrile phae , 2.critical 3. recovery.
FEBRILE PHASE of dengue
high grade fever for 2-7 days
some other features that may accompany fever are-
- facial flushing
- generalized body ache – termed as break bone fever
- skin erythema
- headache retrobulbar pain (pain increases of eye movement)
- sever backache
in children, high grade fever may cause convulsions/seizures, these are called as febrile convulsions.
saddle back fever- in some cases, fever may subside 3-4 days after appearing. there are no symptoms for 2 days and again symptoms return. this bi-phasic or saddle back pattern of fever is considered characteristic of dengue.
mild hemorrhagic manifestations – petechia, mucosal bleed- form mouth or nose or gums.
progrressive decrease in total white cell count
critical phase –
this usually starts on the 3rd or 7th day after starting of fever.
consequences of plasma leakage-
shock – occurs when there is critical volume of plasma leakage
body temperature – may be low/ normal when shock occurs
organ impairment – if shock is prolonged, it causes hypoperfusion of organs and leads to progressive organ impairment, metabolic acidosis and disseminated intravascular coagulation (DIC). this leads to severe hemorrhage and decrease of hematocrit in severe shock. severe organ impairment i.e. severe hepatitis , encephalitits, or myocarditis. and/or severe bleeding may also develop without obvious plasma leakage or shock.
non severe dengue – in many cases, a patient may recover completely after suffering from fever for a few days, and may not go through warning signs and or signs of plasma leakage.
warning signs –
these cases usually recover with early intra venous rehydration.some may progress will progress to severe dengue.
recovery phase –
improvement of general well being
return of appetite
disappearance of gastro intestinal symptoms
stabilization of hemodynamic status and diuresis.
some may complain of generalised pruritis throughout the body.
according to WHO, dengue is considered severe if there is one or more of the following
plasma leakage leading to shock and or fluid accumulation wiht or without respiratorty distress.
severe organ impairment
usually symptoms develop around thethe ime of improvement – 4-5 day.
in dengue,progression of increases ascular permibility due to endothelial dysfunction leads to worsening of hypovolemia and results in shock.
effect of shock-
shock progresses towards the compensatory stage wherein the body tries to correct the probelm by otslelf. once it gets out of control, shock proceeds to decompenstory phase and organ dysfunction sets in.
it may be associated with bleeding abnormlities which may lead to shock, hypotension, thromocytopenia, hypoxia, acidosis. and may eve lead to multiple organ failure and advanced disseminated intra vascular coagulation.
the diagnosis of dengue is done via sample of blood.
changes in CBC
rapid fall in WBC
fall in platelet count
rise in liver enzymes – ast/alt
dengue virus detection
isolation by tisue culture
detection of specific gene of virus RNA – by RT-PCR. in 1st to 5th day . this is most sesnsitive and specific test.
detection of serum NS1 antigen – by ELISA . hihgly specific but less sensitive than PCR. detectable from day 1 and can remain positive till day 18th
detection of antibodies – IgM – first detected after day 5 and within 90 days. IgG is detectable during 14th to 21 days of illness. ELISA method is used to detect the presence of IgG anit-bodies. othe methods to detect anti- bodies include – HAI (hemaglutination method), CFT (compliment fixation test), neutralization test such as plaque reducito test, neutralization and microneutralization tests.
abdominal pain or tenderness
clincial fluid accumulation- ascitis, pleaural efusion
increased hemtocrit along wth rapid fall in platelet count.
complication of dengue
dengue hemorrhagic fever
diseminated intravasclar coagulation
dengue shock syndrome
polserositis acalculous cholecystitis
cerebral hemorrhage or edema
cranial nerve palsies
hemolytic uremic syndrome’
cortical venous thrombosis
vertical transmission (if infection occurs within 5 weeks of delivery)
so far there is no sepicifc treatmen for dengus in particular.
the treatment of dengue mainly aims at maintaining the adequate intra vascular volume, symptomatic treatment and preventing the complications of dengue.
during the course of treatment, it is necesary to undergo thevarious blood reports at regular intervals. this ensures that the blood parameters are in normal range and also , if needed certain complications can be prevented before they show severe symptoms.
measuring proper urine outoput. the mina stay of treatment in dengue is maintaining the water adequate intake. hence it is necessary that the urine output must be hecked all times. this will ensure weather the functioning of kidney is good and if there is oozing of fluid out from blood vessel into the lungs or peritoneum.
maintiannig the proper blood pressure, pulse and repiration.
depending on the clinical condition and the blood parameters of the patient, the patent ca be treated at home or in hosptial .
if there is fall in platelet count, there is excess dehydration or there is presence of high grade fever for many days, a patent may need hospital admision.
in cases, wherein the patient has presence of bleeding from mucous areas or there is presence of ascitic fluid or pleural effusion, the patietn may require admission in ICU.
admission criteria –
fall in platelet count
hydration levels of patient
hemodynamic stat of patient – pulse. blood pressure
presence of warning signs
phase of dengue
presence of rash or other bleeding manifestations
pre-existing medical condition such as pregannacy, old age, diabetes mellitus, renal failrure, chronic hemolytic disease.
social circumstances – living alone, living far from a health care facility.
continuous intravenous fluid
repeated CBC reporting
repeated clicnial assesment
monitor other blood parameters- creatinine, electrolytes and lier function test,
in cases of patient with signs and and symptoms of plasma leak such as – dengue shick, hemorrhages, organ impaiment.
when platelet count drops below 10,000/mm3 or patient develops bleeding problems, platelet transfusion shoudl be started.
if hemoglobun drops below 8gm%. pack red cell transfusion can be done.
if coagulopathy is ppresent, plasma transfusion can be done.
encourage to drink more fluids – these include intake of normal watere plus ORS, fruit juice and other fluids. this will maintain in maintaining the electrolyte levels of the body which have been lost by body during fever and vomiting or while fighting against the disease.
in order to control fever – paracetamol can be used. in case if fever is too high, use of cold water sping can be done.
use of NSAIDS and aspirin should be avoided in such cases.
prevention of dengue
depends on control of vector of mosquito vector or interruption of human-vector contact
control of hman – vector contact
interruption of human- vector contact
currently there is no vaccine or anti viral drug available in mmarket against dengue.
DENGAVAXIA – WHO endorsed 1st ever vaccine for dengue
criteria for dischage
nofever ofr 2 hours without the need for anti-pyretics
platelet count more than 5,000/ mm3
retrun of apatite
good urine output
visibl clinical improvement
mninmum 2-3 days after recovery from shock
no r.s distress from peural effusion/ascitis
high fever – biphasic, break bone fever, saddle back fever
maculopapular rash over chest and upper limbs
muscle and oint pain
loss of apatite
dengue hemmorhagic fever (DHF)
hihg continuos fever
thrombocytopenia (platelet count less than 1 lakh)
raised hematocrit (packed cell volume ) by 20%
evidene of hemorrha – spontaneuous bleeding feom nose/ mouth otr gums
dengue shock syndrome –