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.

incubation period

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
• myalgia
• arthralgia
• malaise
• headache retrobulbar pain (pain increases of eye movement)
• sever backache
• anorexia
• nausea
• vomiting

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.

laboratory findings

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-

pleural effusion

ascites

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.

severe dengus

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 bleeding

severe organ impairment

dengue shock-

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.

diagnosis

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.

warning signs

abdominal pain or tenderness

clincial fluid accumulation- ascitis, pleaural efusion

muscosal bleeding

leahtargy/ restlessness

hepatomegaly

increased hemtocrit along wth rapid fall in platelet count.

complication of dengue

dengue hemorrhagic fever

diseminated intravasclar coagulation

hemophagocytic lymphohistiocytosis

dengue shock syndrome

polserositis acalculous cholecystitis

acute pancreatitis

cerebral hemorrhage or edema

cranial nerve palsies

rhabdomyolysis

hemolytic uremic syndrome’

heapatitis

encephalitis

myocarditis

aseptic meningitis

GB syndrome

cortical venous thrombosis

pericaritis

atrial fibrilation

hert blocks

cardiomyopathy

vertical transmission (if infection occurs within 5 weeks of delivery)

treatment –

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

urnie output

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.

admission

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.

platelet transfusion-

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.

home treatment-

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

dengue fever

high fever – biphasic, break bone fever, saddle back fever

maculopapular rash over chest and upper limbs

frintal headaha

muscle and oint pain

lymphadenopathy

loss of apatite

nausea

vomiting

dengue hemmorhagic fever (DHF)

hihg continuos fever

heaptmagaly

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 –