DETAILED DISCUSSION ON CLASSIFICATION OF Dengue Fever

DETAILED DISCUSSION ON CLASSIFICATION OF Dengue Fever

ASYMPTOMATIC DENGUE PATIENT:

These are the patients who previously had dengue infection. They developed life long immunity against the serotype they got infected with and 6 months immunity against other serotypes. So if the previous serotype infection would occur anytime in life or any serotype infection would occur within 6 months of dengue infection then the patient would remain asymptomatic. He would develop no symptoms and is good to go.

SYMPTOMATIC DENGUE PATIENT:

It’s the patient who develops symptoms of dengue fever. He has not got immunity against the serotype he is being infected with. Now we will discuss that what can be different types of patients in this category
1. UNDIFFERENTIATED FEVER:
These are the neonates who are born to mothers who ever had dengue infection. The mothers developed anti bodies against the serotype they were infected with and those anti bodies travelled through the placenta and got transferred to the baby. Though the baby never got dengue fever but he has got the anti bodies but they are less in number so he has partial immunity. So if baby gets bitten by aedes egypti he would develop undifferentiated fever just like other viral infections in which the symptoms are undifferentiated and not clear. Fever would not be high grade and baby would get fine on its own in couple of days with mild disease.
2. DENGUE CLASSICAL FEVER
Dengue classic fever can be of three types
i) DENGUE CLASSIC FEVER WITHOUT THROMBOCYTOPENIA
Now in these patients after the common duration we will see that there would be no change in CBC. Fever would subside in around 5 days and patient would get fine and might not even know that he had dengue fever. These cases rarely present to doctors and sometimes get fine even by self medication
ii) DENGUE CLASSIC FEVER WITH THROMBOCYTOPENIA WITHOUT UNUSUAL HEMORRHAGES
In these patients after common duration the only change in CBC would be fall in platelet count. Normal platelet count being 150,000 to 450,000 per microlitre of blood. The platelets would start to fall from 4^th day and would keep on falling till 6^th or 7^th day. Fever subsides same way on day 5^th to 7^th. After 7^th day platelets start to rise again on their own. All rest things on the lab tests would be in normal range. In these patients we would not see any presentation of any bleeding from nose or GIT or in cough or any internal bleeding. That’s the reason why this category is named as being “without unsusual bleeding”.
iii) DENGUE CLASSIC FEVER WITH THROMBOCYTOPENIA WITH UNUSUAL HEMORRHAGES
In these patients after common duration again the only change in CBC would be fall in platelet count. Normal platelet count being 150,000 to 450,000 per microlitre of blood. The platelets would start to fall from 4^th day and would keep on falling till 6^th or 7^th day. Fever subsides same way on day 5^th to 7^th. After 7^th day platelets start to rise again on their own. All rest things on the lab tests would be in normal range. In these patients we would surely see any presentation of any bleeding from nose or git or in cough or any internal bleeding. That’s the reason why this category is named as being “with unsusual bleeding”.
3.DENGUE HEMORRHAGIC FEVER:
(Further Classification Of Dengue Hemorrhagic Fever is Explained in the end of this page)
Now is the time to discuss what dengue hemorrhagic fever actually is. Basically the differentiating point between hemorrhagic and other forms of dengue fever is CAPILLARY LEAK. In Dengue hemorrhagic fever the capillaries of patient become leaky and that’s why from 4^th day onwards the intravascular fluid of patient starts oozing out into the extra vascular compartment. But the patient does not get edema which is also a fact. Now due to the transfer of intravascular fluid into the extra vscular compartment we see some typical changes in the lab tests of the patient.
First of all surely the platelets of the patient decrease and the decrease may be more and quicker than what we see in dengue classical fever with thrombocytopenia. The fever may show biphasic pattern as well which is seen in some cases but its not always seen. From 4^th day onwards the hematocrit of the patient starts to increase. Due to capillary leakage and oozing of fluid into extravscular compartment RBCs gets concentrated in the intra vascular compartment and so we see a rise in hematocrit. The diagnostic value is more than 20 percent rise in the reference value of HCT of the same patient. That’s where the CBC of the patient we did in first three days of disease gets beneficial. Further more plasma albumin accompanies the fluid and goes into extra vascular compartment showing a decrease in plasma albumin (less than 3.5d/dl). Moreover the serum cholesterol of the patient may decrease (less than 100) but it may not be a good index as its very variable unless and until we have a recent cholesterol report of the patient in near past. All these derangements would start on 4^th day and would remain for 48 hours after which the capillary leak would stop and all values would start to come back to normal. This period of 48 hours is very dangerous period as we have to manage patient accordingly during this time.
Clinically after three days the features of dengue hemorrhagic fever may be:
Restlessness
Mucosal bleed
Positive hess test or tourniquet test
Platelets less than 100000
HCT increase by 20 percent
Albumin less than 3.5
Cholesterol less than 100
Pain RHC
Ultrasound showing ascites
Xray chest showing pleural effusion

As discussed in General Classification Of Dengue ;
Patient of dengue hemorrhagic fever can present to us in 2 forms :
i) DENGUE HEMORRHAGIC FEVER WITHOUT SHOCK
In dengue haemorrhagic fever without shock we would have all the features described above but the patient would not be in shock and so the pulse pressure of the patient would be normal. Pulse pressure is the difference between systolic and diastolic blood pressure. Keep in mind that 140/130 has low pulse pressure but 90/50 has normal pulse pressure.
ii) DENGUE SHOCK SYNDROME
In dengue shock syndrome we would have all the features of dengue hemorrhagic fever as well as the patient would be in shock and the pulse pressure of the patient would be narrow. Patient may be drowsy, unconscious, having fits etc like presentation.
Its worth stressing again here that a mismanaged case of dengue classic fever does not get converted into dengue hemorrhagic fever and that both diseases start separately from the very beginning though both have same presentation during first 3 days (common period) and can be differentiated usually only after 4^th day.