Dengue - A paradox of prevention and case management

by Prof. Kolitha H Sellahewa

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 an average of 35,000 cases per year. Sri Lanka currently holds the ignoble tag of a hyper-endemic country in the South-East Asian region according to the World Health Organisation with an incidence of 175/100,000 population.

Experts in public health and the Ministry of Health (MOH)with support from the public, otherstate and private sector organizationshad relentlessly pursed its efforts to curb the disease incidence. Dengue is caused by an arbovirus of which there are 4 serotypes.

The vector transmitting the disease is a mosquito of the species Aedesaegypti and A. albopictus.

Preventive methods have primarily addressed the elimination of adult mosquitoes and its breeding sites. Unplanned town development, urbanisation of an unprecedented scale, and improper waste disposal owing to callousness and lack of civic consciousness of the public, compounded by less than optimal government mechanisms for solid waste management are some of the main reasons I could conceptualise for this predicament.

While conceding the importance of prevention we need to reconcile that prevention has not been successful even in clean rich countries like Singapore where the incidence of dengue has increased despite a reduction in the mosquito burden.

Morbidity and mortality

It is against such a background that clinicians like me resorted to develop methods to reduce morbidity and mortality among dengue infected patients by improving case management. Dengue infection results in two fundamentally different clinical types’ viz. dengue fever (DF) and dengue haemorrhagic fever (DHF). DF typically takes an uneventful benign course towards complete recovery. DHF on the other hand has the propensity to develop severe disease with attended increased morbidity and death. Fortunately however DHF has a highly stereotyped predictable course which gives the clinician a window of opportunity for rational and timely appropriate interventions to manipulate the disease course and ensure a shift towards a favourable outcome.

In DHF there is a critical phase setting in between the 3rd to 7th day of the illness (the day on which the fever started is counted as day 1) and typically lasts only 24 – 48 hours. The pathological hall mark in this phase of the illness is plasma leakage with attended intravascular volume depletion that can lead to all the serious complications such as bleeding, kidney failure, liver failure and death.

Judicious fluid therapy in the face of plasma leakage can conceivably offset an adverse outcome resulting from intravascular volume depletion. Early detection of plasma leakage and proper management over the critical 48 hour period can ensure a smooth transition to convalescence and complete recovery.

Astute clinicians with a clear understanding of these fundamental principles have contributed to the success story of dengue. The paradox of success is the reduction in case fatality from 5% in 1996 to 1% in 2009 and the lowest 0.2% recorded in 2014 despite an increased incidence of 47,502 cases in 2014 and also an increase in the proportion of DHF, the more severe form of the disease to 10-15%.

Case management

The road to this success was never an easy one. My first attempts to improve case management started as far back as 1990. I resolved to manage dengue patients by applying simple physiological principles in fluid therapy and also avoiding platelet transfusions despite drops in the platelet count and often digressing from accepted WHO guidelines on fluid therapy in that era. This approach was controversial and was not accepted and opposed by the medical fraternity at large when presented in academic fora. Nevertheless I resorted to do what I thought wasintrinsically right resigning to change only the microenvironment in which I worked. The success story was then only an individual one with only one death among > 3,000 patients treated under my care up to 2008. The only death was in 1997. This was a patient who came late in the disease course with massive bleeding and died within 2 hours of admission to the state hospital where I was then working.

It is only after I retired from the department of health services that I got the best opportunity to impact case management at a national level. Shaken by the biggest dengue epidemic Sri Lanka experienced in 2009 with 35,010 cases and 346 deaths dengue assumed a place of grave concern in the political arena.

The epidemiology unitheaded by the chief epidemiologist Dr Paba Palihawadana along with dengue prevention unit of the MOH which was doing a tremendous job related to dengue till then received the ministerial backing to escalate their work. Towards this end they employed Dr Jayantha Weeraman (a consultant paediatrician) and me in 2010 to provide expert technical assistance to improve case management of severe paediatric and adult dengue cases.

We were also assigned the sensitive and arduous task of conducting an in-depth clinical/death audit of dengue case management in Sri Lanka.

We filled the void of clinical expertise in the epidemiology unit and the two of us utilised our profound clinical experience to give inputs to develop a collective strategy with other clinicians to reduce dengue related deaths.

(The writer is Professor of Medicine, South Asian Institute of Technology & Medicine, Dr Neville Fernando Teaching Hospital, Malabe)