Dengue fever, a very old disease, has re-emerged in the past 20 years with an expanded geographic distribution of the viruses and the mosquito vectors, increased epidemic activity, the development of hyperendemicity and the co-circulation of multiple serotypes. In 1998 this mosquito-borne disease was the most important tropical infectious disease after malaria, with an estimated 100 million cases of dengue fever, 500,000 cases of dengue hemorrhagic fever, and 25,000 deaths annually in the tropics. The reasons for this resurgence and emergence of dengue hemorrhagic fever in the waning years of the 20th century are complex and not fully understood, but demographic, societal, and public health infrastructure changes in the past 30 years have contributed greatly. Here Dr Amit Saraf, consultant internal medicine, Jupiter Hospital, Mumbai.
What is the reason behind the increasing number of dengue cases in India?
Dengue fever is caused by A. aegypti mosquito-transmitted flavivirus, which occurs predominantly in the tropical and subtropical regions of the world. Dengue virus has four serotypes. After mosquito bite, the virus replicates in the human body and symptoms start after a sufficient number of viruses invade and overwhelm body’s immunity. This is called the incubation period. Lack of sanitation and proper hygiene gives these mosquitos a breeding ground. The manifestations of dengue infections are protean from being asymptomatic to undifferentiated fever, severe dengue infections and unusual complications.
The patients usually go through the following phases:
- Febrile phase
- Critical phase
- Recovery phase
What are the typical symptoms?
The symptoms include body pain, headache, fever with chills and occasionally rashes on the skin too. The body ache is much more pronounced compared to the fever, hence Dengue virus was aptly named ‘Break bone fever’ when first discovered, due to the severe body pain accompanying the infection. Two major complications of dengue infection include bleeding diathesis and organ failure (such as lung, liver, kidney). These complications are predominantly seen in immune-compromised individuals such as diabetics, HIV positive patients, extremes of ages etc. Hence such individuals having complaints of fever should seek timely medical attention.
Are there any warning signs?
Warning signs of dengue usually precede the manifestations of shock and appear towards the end of the febrile phase, usually between days 3–7 of illness. Persistent vomiting and severe abdominal pain are early indications of plasma leakage and become increasingly worse as the patient progresses to the shock state. The patient becomes increasingly lethargic but usually remains mentally alert. These symptoms may persist into the shock stage. Weakness, dizziness or postural hypotension occurs during the shock state. Spontaneous mucosal bleeding or bleeding at previous venepuncture sites are important haemorrhagic manifestations. Increasing liver size and a tender liver is frequently observed. However, clinical fluid accumulation may only be detected if plasma loss is significant or after treatment with intravenous fluids. A rapid and progressive decrease in platelet count to about 100 000 cells/mm3 may be the earliest sign of plasma leakage. This is usually preceded by a low white cell count (≤ 5000 cells/mm3 )
How is dengue diagnosed?
Diagnosis of Dengue infection is on a clinical judgement, looking at the symptoms and signs. Laboratory investigations are used as supportive evidence. These tests include blood investigations such as Dengue NS1 antigen test, Dengue IgM test and Dengue IgG test, RT-PCR.
How is it treated?
Treatment is purely symptomatic, which includes given IV fluids for hydration, paracetamol for fever and body pain, vitamin supplementation etc. Platelet transfusions are given as per the rapidity of the fall of platelets, evidence of bleeding diathesis etc. No food or medicines can raise the platelet count. Early recognition of symptoms and quick medical intervention can prevent dengue from causing morbidity and mortality.
Avoiding mosquito breeding by preventing water stagnation, good personal immunity by good nutrition and regular exercise can prevent dengue infection. Attempts are underway for the development of a vaccine for preventing the burden of this neglected disease.