By Dr Rishu Agarwal, MD (Pathology)
Introduction
Dengue is the most common mosquito-borne viral disease of humans that in recent years has become a major international public health concern. Globally, 2.5 billion people live in areas where dengue viruses can be transmitted. Today emerging Dengue hemorrhagic fever (DHF) cases are causing increased dengue epidemics in the Americas and in Asia, where all four dengue viruses are endemic. DHF has become a leading cause of hospitalization and death among children in several countries.
Geographical distribution
Caribbean countries contribute 3.9% (168,819) of total cases around the globe, with 2217 DHF cases and 284 deaths according to WHO-2009. Countries with the highest number of dengue cases in the Latin Caribbean were Cuba, Puerto Rico and the Dominican Republic, whereas in the English and French Caribbean, Martinique, Trinidad and Tobago and French Guiana reported the highest number of cases. The Dominican Republic reported 77 deaths from dengue (220) during the period 2001-2007. All four serotypes circulate in the Caribbean area, but the most common are DEN-1 and 2.
Clinical presentation
Dengue has a wide spectrum of clinical presentations, often with unpredictable clinical evolution and outcome. While most patients recover following a self-limiting mild clinical course, a small proportion progress to severe disease, mostly characterized by plasma leakage with or without bleeding.
Symptomatic dengue virus infections progress in three phases
Febrile phase: Patients typically develop high-grade fever suddenly. This acute febrile phase usually lasts 2–7 days and is often accompanied by facial flushing, skin erythema, generalized body ache, muscle pain, joint pain and headache. Some patients may have a sore throat, congested pharynx and red eyes. Nausea and vomiting are common.
Mild bleeding manifestations like reddish spots on body and mucosal membrane bleeding (eg nose and gums) may be seen. Massive vaginal bleeding (in women of childbearing age) and gastrointestinal bleeding may also occur during this phase. The liver is often enlarged and painful on touch after a few days of fever. The earliest abnormality in the full blood count is a progressive decrease in total white cell count, which should alert the physician to a high probability of dengue.
Critical phase: When the temperature drops to 37.5-38oC or less and remains below this level, usually on days 3-7 of illness, an increase in capillary permeability occurs which results in the leaking of fluid from small blood vessels and the blood becomes thick. This marks the beginning of the critical phase. The period of clinically significant fluid leakage usually lasts 24-48 hours. This may result in the collection of fluid in lungs and abdomen and the patient can go into shock and circulatory failure. Most of the deaths occur in this phase.
Recovery phase: If the patient survives the 24-48 hour critical phase, a gradual reabsorption of fluid takes place in the following 48-72 hours. General well-being improves, appetite returns, and urine output increases. Some patients may have a rash looking like “isles of white in a sea of red.” Some may experience generalized itching.
Diagnosis
Early, efficient and accurate diagnosis of dengue is of primary importance for clinical care. Routine tests like complete blood counts, liver function tests, etc, should be done in each suspected case of dengue fever.
A pattern of increasing hematocrit (marker of blood viscosity), decreasing leucocyte counts and a fall in platelets is highly suggestive of dengue. Laboratory diagnosis methods for confirming dengue virus infection may involve detection of the virus, viral nucleic acid, antigens or antibodies, or a combination of these techniques.
Most of these techniques are not available in routine laboratories at a reasonable price. Until recently serology (Ig G and IgM antibodies to dengue virus) used to be the only practical and reliable way of diagnosing dengue infection. The major drawback with serology is that it is not positive in the early phase of illness. Hence the need for a new, reliable and easily assessable test has long been felt that can help in diagnosing infection in its early phase.
Recently a breakthrough has been achieved in this regard with discovery of the Dengue NS1antigen detection test as a diagnostic tool in the early detection of dengue infection. It becomes positive by the 2nd day of illness and is detectable up to the 9th day. It has been highly successful across the world in timely diagnosis of dengue and its correlation with antibody levels is excellent. It is now available in Guyana.
Management
There is no specific treatment and no curative drug is available so far. Management is mainly supportive and includes rest, paracetamol for relief of fever and pain and plenty of fluids. Never use aspirin or other over-the-counter pain killers like ibuprofen (Motrin). Always watch for the bleeding symptoms of dengue haemorrhagic fever.
Recognition of the high risk patient
● Fever patients have red spots on skin (petechiae), bleeding from gums or nose, vomiting of blood.
● Patients who remain ill (despite drop in temperature) and whose general condition deteriorates.
● Clammy skin, cold and sweaty extremities, drowsiness, and/or restlessness.
High fever with bleeding symptoms – rush to hospital
● Blood spots under the skin (petechiae)
● Bleeding from gums
● Nose bleeds (epistaxis)
● Vomiting of blood (haematemesis)
Fluid management in hospital is critical.
Platelet transfusion can be vital.
Preventive strategies
Prevention by environmental control of breeding containers
● Old tyres – dispose of, cover, or fill with earth
● Water storage (tanks, drums, jars, overhead tanks, coolers) – Cover to keep out mosquitoes (can use rustproof mesh or screen) and add Abate® (temephos) to kill larvae in the water
● Small containers and garbage – clean up/bury/burn
● Cooler and drip-pans, flower pots, animal water dish, ant traps, etc- Empty water every week, both indoors and outdoors
Personal protection
● Mosquito repellant when outdoors during daytime
● Mosquito screens on doors and windows
● Mosquito coils or vapour mats
● Mosquito nets for children or elderly who sleep during the day
● None of these are effective by themselves, use them in combination
