Dengue
is a mosquito borne infectious disease caused by the dengue virus which is
mainly found in the tropical regions. Dengue fever, also known as breakbone fever, because
produces body pains as one feels when his/ her bones break.
About 40% of the world’s population is
at risk and there are 50–100 million cases every year. An estimated 500 000
people with severe dengue require hospitalization each year and about 2.5% of
those affected die. In India, dengue is widespread and endemic in most major
cities.
There are four Dengue
viruses (DENV) that cause Dengue fever, all of which are spread by a species of
mosquito known as the Aedes aegypti mosquito, and more rarely
by the Aedes albopictus mosquito.
Aedes
aegypti is the main carrier, responsible for approximately
two-thirds of the world’s dengue. The virus is transmitted from an infected
mosquito to human. The process begins when a person who is infected with the
Dengue virus is bitten by a mosquito, the virus is then passed on when someone
else is then bitten by the infected mosquito.
The dengue virus is divided into four viral serotypes, DEN1, DEN2,
DEN3, and DEN4, which are closely related but differ in their antigens.
The Aedes aegypti species of mosquito breeds in stagnant water and
usually bites during daylight hours. The virus circulates in the blood for 27
days after the human is affected, during which the mosquito may acquire the
virus by biting the infected human and spread it to another unsuspecting
victim.
Symptoms: of dengue includes fever, headache, bone or joint pain, muscular
pain, rash, pain behind the eyes, petechial hemorrhagic complications. Low
platelets count (<100,000 platelets mm−3) leads to hemorrhagic complications such as bleeding from the gums,
nosebleeds, and bruising.
Diagonosis: Laboratory confirmation of dengue infection is
crucial as the broad spectrum of clinical presentations, ranging from mild
febrile illness to several severe syndromes, can make accurate diagnosis
difficult.
Methods for dengue diagnosis:
Virus isolation:
The detection of the viral genome or viral antigens provides the evidence
infection. Sera that have been collected from suspected dengue cases in the
first 3–5 days of fever (the viraemic phase) can be used for virus isolation.
After an incubation period permitting virus replication, viral identification
is performed using dengue-specific monoclonal antibodies in immunofluorescence
and PCR assay.
Serological testing: When a dengue infection
occurs in individuals who have experienced a previous dengue infection, a
secondary immune response occurs, which generates high levels of IgG through
the stimulation of memory B cells from the previous infection as well as an IgM
response to the current infection. Because high levels of IgG compete with IgM
for antigen binding, an IgM capture assay can be used.
Polymerase Chain Reaction (PCR): detects
viral genomic sequence from Serum or Cerebro Spinal Fluid (CSF) samples
collected from the patient.
Nucleic
acid-sequence based amplification assay (NASBA): The NASBA assay is an isothermal
RNAspecific amplification assay that has been adapted for dengue virus.
Antigen detection: Dengue
antigens can be detected in tissues such as liver, spleen and lymph nodes using
an enzyme and a colorimetric substrate with antibodies that target
dengue-specific antigens.
Haemagglutinationinhibition
test: This test is based
on the ability of dengue antigens to agglutinate red blood cells (RBC) of ganders
or trypsinized human O RBC. Antidengue antibodies in sera can inhibit this
agglutination and the potency of this inhibition is measured in an HI test
Haematological
tests: Platelets and haematocrit values are commonly measured during the
acute stages of dengue infection. These should be performed carefully using
standardized protocols, reagents and equipment.
A
drop of the platelet count below 100 000 per μL may be observed in dengue fever.
Thrombocytopaenia is usually observed in the period between day 3 and day 8
following the onset of illness.
Increase
in hematocrit i.e., the volume percentage of Red Blood Cells (RBS), by 20%
should be a caution as it occurs due to rise in the vascular permeability of
the plasma.
Treatment:
There
are no specific antivirals that can eliminate the virus from an infected
individual. However, supportive care and treatment can be effective in treating
Dengue fever. Paracetamol and other antipyretics can be used to treat fever.
Bone pain should be treated by analgesics or painkilling tablets.
The
patient can also be treated with natural home remedies such as papaya leaves,
kiwi and other food items that have been proven to help in the increase of
platelet count, which gets affected during dengue
During
episodes of Dengue hemorrhagic fever/Dengue shock syndrome, the mortality rate
in the absence of hospitalization can be as high as 50%. With proper treatment,
such as intravenous fluid replacement, the mortality rate is greatly reduced.
Patients
should drink plenty of fluids, as dehydration is prevalent among those affected
with Dengue. Vaccines for all of the serotypes are being developed, which will
be the most effective way to cure the disease.
Prevention
of Dengue:
Since
the vaccine is under development for treating dengue, the best method of
prevention is to avoid being bitten by mosquitoes.
ü If you live or travel
to an area where dengue exists, there a number of ways to avoid being bitten
ü The Aedes mosquito
prefers to breed in clean, stagnant water. It is important to frequently check
and remove stagnant water in your home/premises. Water
should be stored in closed containers
ü Bleaching
powder may be used in water sources that are not meant for drinking, as it
prevents the development of mosquito eggs
ü The
female mosquito feeds on blood as it requires the blood protein to produce
eggs, hence it is better to use mosquito repellents, even when indoors
ü It
is advised to reside in a well screened or air conditioned house. If not,
mosquito nets may be attached to the windows
ü Usage
of long sleeved shirts, boots, socks and long pants is advised when outdoors
ü It
is healthier to avoid being outdoors during dawn, dusk or early evenings when
mosquitoes tend to roam around in the open.
ü Mosquitoes
are attracted to dark colored clothing hence it is better to wear bright and
light colored clothes
ü Avoid
strong perfumes, as mosquitoes are drawn towards strong body odor’s.
References:
2.
Cecilia D: Dengue and chikungunya in
India. WHO South-East Asia Journal of Public Health ; 2014 |:3 (1) : 22-27.
3.
Maria g. guzman, scott b, halstead. Dengue: a continuing global threat. Nature
reviews | microbiology.2010;16-17.
4.
Viroj
Wiwanitkit. Dengue fever: diagnosis and treatment .Expert Rev. Anti Infect. Ther. 8(7), 841–845 (2010).
