Dengue was known to mankind for over 200 years and was not considered to be a major public health concern for several decades. A resurgence of interest in this age-old disease arose only after it ravaged mankind with several epidemics. The first pandemic was in 1998. Sri Lanka experienced her first epidemic in 1989 with an exponential increase in incidence ever since with a number of cases rising annually. Consequently Sri Lanka currently holds the ignoble tag of a hyper-endemic country in the Southeast Asian region according to the World Health Organization. Dengue is caused by an arbovirus of which there are four serotypes. The vector transmitting disease is spread by Aedes aegypti and A. Albopictus species of mosquito types. Preventive methods have been primarily addressed for the elimination of adult mosquitoes and its breeding sites.
Dengue fever dominated news throughout Sri Lanka during the last few weeks with warning lights flashing towards an approaching another epidemic with various suggestions to combat the malady including President Maithripala Sirisena's declaration on war on dengue. From January 2017, up to mid-May, 50,000 cases have been reported with more than 125 deaths so far.
"Dengue is considered a killer disease and is sought with much fear by the lay public, but in reality the vast majority of patients recover completely. The onus of reducing the morbidity and mortality of dengue remains not only with physicians attending to patients alone, but also with the patient and relatives of the patients”, says Prof. Kolitha H. Sellahewa, Professor of Medicine / Consultant Physician and Head of Department, Department of Internal medicine at Dr. Neville Fernando Teaching Hospital, Malabe.
The writer was privileged to meet up with Prof. Kolitha H. Sellahewa recently and was able to learn that in the absence of an effective vaccine to combat the disease, some of the main reasons that could conceptualize the predicament would be the unplanned town development, urbanization of an unprecedented scale, improper waste disposal, callousness and lack of civic consciousness of the public, compounded by less than optimal government mechanisms for solid waste management.
This will mean by not adhering to a particular 'Dengue Day' or 'Dengue Week' but awakening of the civic responsibility to be conscientious in the proper garbage disposal on a daily basis, as much as local councils taking the full accountability on drainage of water, disposal of domestic waste and clearing of water logged canals and waterways regularly. Without such practical constraints, the role played by hospitals and medical teams, with a sound understanding and case management of the disease on fluid therapy alone will be non-productive.
Prof. Sellahewa states that the infection of dengue virus produces a gamut of clinical disorders ranging from a completely a symptomatic stage to dengue fever, dengue haemorrhagic fever and more serious but rare and often fatal dengue shock syndrome (DSS). Dengue being a viral infection and not having a specific antiviral drug, the disorder has to run its own course and heal itself by one's own defences and healing mechanism. In this respect the provision of proper nutrition, physical and mental rest at home or hospital is of crucially important. His advice to both patients and relatives is to bear in mind that there is no magic cure overnight for dengue.
To reduce the risk of an adverse outcome, his paramount advice is the early diagnosis and proper treatment. The common clinical diagnostic symptoms are acute fever, headache, retro-orbital pain, muscle pain, and arthralgia (pain in the joints). In this regard, he believes in the availability of new diagnostic tools and amenities will facilitate early diagnosis with greater accuracy. Normally a full blood test for dengue NSI antigen helps to detect from the initial stages of infection. He says it could remain positive up to 4-5 days of the viraemic phase (The presence of viruses in the bloodstream), but it would not be detectable during convalescence.
Eighty per cent of all dengue cases have detectable IgM antibody. (IgM is by far the physically largest antibody in the human circulatory system). It is the first antibody to appear in response to initial exposure to an antigen by day five of illness, and 93-99 per cent of cases have detectable IgM by day six to 10 of illness, which may then remain detectable for over 90 days. IgM antibody is detectable in most cases after seven days. Kinetics (reaction rate) of the immune responses and the tendency for false positive results limit the utility of serology (diagnostic identification of antibodies in the serum) for early diagnosis.
In Prof. Sellahewa's assessment, a full blood count (FBC) should be done from two to three days of the patient complaining of any of the symptoms mentioned above to be followed daily or more frequently depending on the case. Taken in conjunction with the clinical features FBC is useful for an early working diagnosis of dengue infection. While NSI antigen test is used for accurate early diagnosis, the results of the FBC are used for treatment decisions. The comparative significance of the different tests, its correlation to the phase of the illness, intelligent interpretation and therapeutic applications become crucial to ensure a satisfactory outcome.
Prof. Sellahewa believes that each patient is unique and interventional decisions are based on an analysis of all the available information and clinical impressions, and not on isolated blood counts. Such decisions are thus best left to the judgment of the attending physician who will know what is best for that particular patient. He also notes that a reduction in the platelet count referred to as thrombocytopenia causes a lot of anxiety and concern among patients, relations, doctors and nurses alike.
Thrombocytopenia, he explains, is exceedingly common in dengue and conceivably associated with severe disease. But what is very important to remember would be that it is only one of the markers of disease severity, and the majority of patients with thrombocytopenia do not progress to DSS and merely alerts one to manage such patients carefully over the critical period of 24 to 48 hours, after which there is a spontaneous rise in the platelet count. It is exceptional and exceedingly rare for a patient with thrombocytopenia to receive platelet transfusions even with counts as low as 10,000 c.mm, he asserts, and went on to state about a patient he managed recently where the platelet count dropped to 1000 c.mm but did not receive platelet transfusions.
He advises fluid therapy should be appropriate to the phase of illness and most will require only oral fluids during the febrile phase. The judicious use of intravenous fluids for selected patients during the critical phase of plasma leakage forms the cornerstone of hospital-based management and is designed to prevent progression to DSS. A quantum of fluid calculated for the ideal body weight or actual body weight, whichever is lower, is infused over the critical period of 24-48 hours.
Easily determinable bedside clinical parameters are utilized to base interventional decisions, as well as the ending and optimization of fluid therapy. Sagacious fluid therapy can prevent life threatening complications and ensure a smooth transition to convalescence and recovery. While conceding the importance of sustained efforts in preventing dengue, his advice, to infected patients and relations, is for them to learn to cooperate with the attending physician and remember the important role they too (relations) have to play to reduce morbidity and mortality due to dengue