Dengue fever
What is dengue ?
Dengue is a viral illness that is transmitted by mosquitoes. It is a zoonotic disease meaning that the virus is actually transmitted from the animal host to the mosquitoes and then to humans. Unfortunately if a mosquito gets infected with dengue virus it will possess and transmit it lifelong without requiring animal host.
What are the common signs and symptoms ?
Dengue fever presents as high grade fever, with nausea, vomiting, abdominal pain, headaches, myalgias or even diarrhoea or rhinitis. Fever is usually followed by a rash that later becomes itchy. Symptoms usually subside in 4-5 days, followed by recovery phase in which platelets drop and minor mucosal bleed like nose or gum bleed may ensue. Itching and rhinitis may persist for another week. Relative bradycardia is also seen with dengue.
Is it life threatening ?
Dengue is a self limiting illness, a large number of people infected with dengue recover spontaneously, although a few subset of patients may have dengue with warning signs and if not managed appropriately this group of patients may become critical with multiorgan dysfunction..
How to diagnose dengue ?
Laboratory diagnosis of dengue is based on serology i.e detection of antigen or antibody from human sera. Different labs have different kits that target various antigens and antibody. Different antigens present at different phases of illness e.g Kit meant to detect NS1 antigen on dengue virus can be used to detect dengue in the first couple of days whereas kit meant to detect dengue antibody ( IgM) can only be used in the second week of illness. Labs at Aga Khan University Hospital can check for both Dengue NS1 antigen and dengue IgM. Patient needs to submit only a couple of cc of blood for dengue testing.
What other lab abnormalities are seen in dengue ?
Liver enzymes especially transaminases may be elevated, coagulation profile (PT/APTT) may be deranged, raised hemglobulin/hematocrit and low platelets, if acalculus cholecystitis occurs than alkaline phosphatase and gamma GT may also be raised. Creatinine and BUN indicate dehydration and kidney involvement.
Does everyone with dengue needs hospitalization ?
No, if people can assure adequate hydration at home there is no need for hospitalization. Even decrease platelets upto 10,000 – 20,000 without any bleed doesn’t need admission to the hospital.
Dengue fever with warning signs, patients with profuse nausea or vomiting who need parenteral fluids, and those who have overt bleeding, need to be managed and observed in a hospital.
What are the warning signs ?
1. Abdominal pain or tenderness, 2. mucosal bleed, 3.enlarged liver, 4.lethargy or irritability, 5.increasing hematocrit with rapidly decreasing platelets, 6.persistent vomiting, 7.clinical fluid accumulation. Most of these signs are indicative of capillary leak which if not managed appropriately can have adverse outcomes.
Does decrease in platelets need transfusion ?
Not necessarily usually in viruses like dengue decrease platelet count is a transient phenomenon that rarely causes serious bleeding, even at platetlet count of 10,000 patients rarely bleed and do not require transfusion. Only if patients have some bleeding disorder or having significant bleed then platelets are must.
What is the treatment of dengue ?
Dengue virus is a self limiting illness, till yet antivirals have not demonstrated any benefit. Symptomatic care with painkillers, antipyretics like paracetamol and adequate fluid intake ensures rapid recovery.
How can we prevent Dengue Shock ?
The reason for dengue shock and multiorgan failure in dengue is capillary leak, meaning intravascular volume depletes and fluid accumulates extravascularly causing puffiness and swelling. As this occurs the volume of blood circulating decreases and body goes in a protective mode that is vasocontriction trying maintain circulation with little volume it has, evident by decrease urine output. In this critical phase the most important therapy is fluid replacement ideally with isotonic fluid. Early and aggressive fluid management can prevent dengue shock.
Is there a vaccine for prevention ?
Efforts are underway for the development of vaccine, but yet we dont have it yet.
What are the factors responsible for dengue fever outbreaks?
The occurrence of DF outbreaks is linked to number of factors such as density of vector (Aedes aegypti), source (an infected febrile person) and presence of susceptible hosts in the community.
What factors increase the density of Aedes aegypti?
Aedes aegypti is commonly found in urban dwellings ,both indoors and outdoors. Therefore, fast urbanization and dense population facilitates the progress of outbreak
How to prevent dengue fever ?
Protective clothing, mosquito repellents, vapourizers, use of preventive nets, insecticides, preventing water from accumulating around the house where mosquitoes breed, are a few things that can prevent dengue.
Myth Buster
Written by Senior Vector Control specialists Muhammad Mukhtar, who highlights what is being done and what needs to be done in a evidence based article………………..Read more
