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Dr Shivani Gandhi
Dengue fever or Dengue continues to pose a significant public health problem in tropical and sub tropical areas of theworld, including parts of Asia, Africa, the Caribbean, and Central and South America. It is considered by the World Health Organisation (WHO) as a major global public health challenge in the tropic and sub-tropic nations. The incidence of dengue has grown dramatically worldwide in recent decades, with cases reported to WHO increased from 505430 cases in 2000 to 5.2 million in 2019. Factors like increased population growth rate, global warming, inefficient mosquito control, unplanned rapid urbanisation etc. have led to a rapid surge in dengue cases.
Some of the important questions that arise in the minds of the common public related to dengue are:
What is dengue?
It is a viral illness caused by the Dengue virus that belongs to the Flaviviridae family. Dengue is divided into four serotypes categorised as DEN-1, DEN-2, DEN-3, and DEN-4. Knowing that infection with one serotype can provide lifelong immunity against that specific serotype is essential.Therefore,anindividualissusceptibletobeinfectedwiththeotherthreeserotypes.
How is the dengue virus transmitted?
The dengue virus transmission occurs through the bite of an infected female mosquito of the genus Aedes that carries and spreads the dengue virus from one infected individual to the other. The primary vector that transmits the virusis most commonly Aedesaegypti and, to a lesser extent, Aedesalbopictus.
When this mosquito bites a person infected with dengue, the virus gets picked up by the mosquito as a part of its blood meal when it feeds on human blood. The virus reaches the mosquito’s gut, stays therefor a few days, and undergoes replication before disseminating to secondary tissues, including the salivary gland. Thus, it becomes capable of spreading the infection to healthy humans it bites and feeds on. This is how the cycle continues. Thus, mosquitoes play a vital role in the transmission of dengue virus.
In which season does the Dengue infection occur?
There is a widespread global distribution of dengue geographically, influenced by various factors like rainfall, temperature, relative humidity, etc.
The arrival of the monsoon, in addition to bringing freshness and relief from the scorching heat, also opens the floodgates for various diseases, dengue being the most common. Various factors like increased humidity, warm temperature and collection of stagnant water act as favourable and ideal conditions for the breeding of mosquitoes, contributing to increased dengue cases in the rainy season.
In India, the monsoon arrives in June/July and lasts till October/November, with dengue fever being synonymous with the monsoon. It raises the need to take proactive measures to protect ourselves and our community during this rainy season from this dreaded illness.
What are its symptoms?
The dengue virus symptoms usually appear in 4-7 days and last for 10 days. Being a viral illness, the symptoms of dengue can be mistaken for other flu-like illnesses. Most of the cases remain a symptom at present with mild symptoms as listed:
* High-grade fever (1040F or more)
* Headache
* Bodyaches
* Retroorbital pain (pain behind the eyes)
* Muscle or bone pains
* Nausea, Vomiting
* Diarrhoea
* Rashes
The majority of the patients are asymptomatic or present with the above-mentioned symptoms in a mild form. Severe forms of dengue include Dengue haemorrhagic fever (DHF), and Dengue shock syndrome (DSS).
And approximately 1 in 20 patients with dengue infection develop severe illness that requires hospitalisation.
The following are the warning signs or red alerts that signal the development of severe dengue.
* Persistent vomiting
* Mucosal bleeding like nosebleed or bleeding gums, passing blood in stool, urine or vomitus.
* Severe abdominal pain
* Lethargy
* Sudden fall in blood pressure.
* Cold and clammy skin
* A weak and rapid pulse
Patients with weak immune systems or immuno compromised individuals, or those with second or subsequent dengue infection, are believed to be at increased risk for developing severe forms of dengue.
What are the tests available for its diagnosis?
Diagnosis of dengue based on the clinical presentation is difficult as it can resemble other illnesses like Chikungunya, Zika virus, malaria and typhoid fever. Thus, confirming dengue with a blood test is important to establish an accurate diagnosis. Blood tests are done to detect the viral antigen or antibodies.
Tests may include:
==>Complete blood count(CBC):it is done to detect
* Hemoglobin level
* Hematocrit
* Platelet count
==>Dengue serology tests :to detect the IgG and IgM antibodies produced by the immune system in response to thevirus.
==>Dengue virus antigen detection: to confirm the dengue infection by detecting NS1antigen.
==> Other tests: Coagulation study, ultrasound abdomen, RT-PCR
How is it treated?
No specific drug or treatment is available for the dengue virus till date. Being a viral illness, dengue needs to run its course. Symptomatic treatment is given to combat fever, body pains, headaches , or other symptoms. In addition to this, proper body rest and adequate fluid in take to stayhydrated are prescribed.
In cases with severe dengue, intravenous fluids and electrolytes are required, along with monitoring of Blood pressure and other vitals. Blood transfusion or platelet transfusion may also be required in severe cases.
What are the preventive measures?
Eliminating egg-laying sites of mosquitoes is the best preventive measure as it will help lower the number of eggs, larvae and pupa to reduce the number of adult mosquitoes, and transmission of infection will be reduced.
Some of the important preventive measures are listed below as do’s and donot’s:
Do’s
* All the water tanks are to be covered with lids
* Unused containers coconut shells are to be disposed of properly
* Regular change of water in flower bases, pots, coolers and earthen pots.
* Wearing full-sleeve clothes and long pants before stepping out of the home.
* Use of mosquito repellents, sprays, coils or nets to prevent mosquito bites.
Donot’s
* Don’t allow water to stagnate in and around houses in flower pots, buckets, coconut shells, earthen pots, etc.
* Avoid being outdoors in dark and dusky places where mosquitoes are more active.
Myths and facts related to Dengue infection
(The writer is Assistant Professor Department of Pathology AIIMS, Jammu).
