 Curse
of the Aedes
Can we prevent another dengue epidemic?:
by Carol Aloysius
As Sri Lanka hovers on the
periphery of another dengue epidemic with the number of dengue suspected
case the first five months of this year nearing the 15,000 mark, Health
officials have reiterated their call for cleaner environments and a
clean sweep of all possible mosquito breeding sites, following the
monsoonal rains. According to the Epidemiology Chief, Dr Paba
Palihawadana, the suspected cases for the first five months of the year
now stands at 14, 979 with the highest number (46.87%) reported from the
Western Province. Health officials attribute this surge to overcrowded
unsanitary dwellings and unclean environments, and admit that despite
awareness raising programmes, people are still unaware of how the
disease is transmitted or its dire health consequences if afflicted by
the more serious types of dengue.
Here, two eminent health officials
in charge of dengue control activities in the Western Province, which
has the highest incidence of suspected dengue cases, explain how dengue
can detected, prevented and the current strategies used to fight the
deadly Aedes aegypti.
Q:What is dengue?
A: It is an infection caused by a virus transmitted by the
Aedes aegypti and Aedes albopictus.
Q:When a patient gets an attack of dengue is he resistant to
the disease thereafter?
A: There are four subtypes of the virus: DEN 1, DEN 2, DEN 3,
DEN4. Therefore a human can contract dengue fever four times during the
life time.
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Those most at
risk
*Children – As the Aedes mosquitoes are
day biters, school going children are more vulnerable to get
infected with the dengue virus.
*Elders, obese people, persons with
chronic diseases (eg: nronchial asthma, diabetes)
* Persons with immunodeficiency
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| Dengue is……
 Chief
Medical Officer, Dehiwala, Mt Lavinia, and Ratmalana ,
Dr INDIKA ELLAWELA explains
how dengue is spread, who is susceptible and the havoc it
can cause. |
Q:What do you know about dengue mosquito?
A: It’s a very active small black mosquito. The female Aedes
mosquito is the vector of dengue.
It bites several people to get one blood meal. It bites mainly the
mornings and evenings.
The life span of an adult Aedes mosquito is around 2-4 weeks and lays
eggs around 100-200 eggs at a time, four times during its life span. The
eggs are sticky, therefore difficult to remove.
It takes 7-11 days for the adult mosquito to emerge from the egg,
which can remain live up to one year in dry conditions and hatch on
contact with water.
Q:What happens when someone is infected with the dengue virus?
A: Around 90% of people infected with dengue virus for the
first time do not show symptoms and signs. But they have dengue virus in
their blood for 5-7 days.
During this period, if they are bitten by mosquitoes, the virus can
enter into these mosquitoes with the blood meal and multiply within the
mosquitoes. These infected mosquitoes can transmit the virus to healthy
people. So you may have already contracted dengue fever for the first
time with or without your knowledge. Once the virus enters your body it
will take about 7-10 days to develop symptoms and signs.
 When
a person infected with one subtype of dengue virus, antibodies are
formed against that subtype and he/she will be protected for that
particular virus subtype in the future, but not protected for remaining
three subtypes. Therefore, they can contract dengue fever again by any
of other three subtypes of virus. When a person contracts dengue fever
for the 2nd, 3 rd, or 4th time, the disease is more severe than
1st episode and possibility of developing Dengue Haemorrhagic Fever is
high.
Q:What are the different types of dengue commonly found in Sri
Lanka?
A: Many patients infected with dengue virus remain
asymptomatic. Others can develop any one of the following febrile
illness:
· Undifferentiated fever
· Dengue Fever (DF)
· Dengue Haemorragic Fever (DHF) –most serious. Here, the patient
goes through three different phases – 1) Fever phase, 2) Critical
(Leakage) phase and 3) Convalescent (Recovery) phase
Q:When or how does one suspect dengue illness?
A: Presence of the following clinical features with acute
onset of fever.
· Headache and retro-orbital pain
· Nausea and vomiting
· Joint pain (Arthralgia) and muscle pain (myalgia)
| The three phases of
dengue
Fever phase – This usually last for 2-7
days during which the patient can have body aches and pain,
muscle pain, severe headache, pain behind the eyes, vomiting
and rash(red colour). Sometimes there can be sore throat and
congestion of eyes (red eyes). These symptoms are similar in
both dengue fever and dengue haemorrhagic fever. Sometimes
fever can subside abruptly, but the patient’s condition
deteriorates and he/she cause complications. Therefore
monitoring the patient’s general condition, adequate rest
and fluid intake will be helpful in preventing
complications.
Critical phase- This is usually evident
after the 3rd day of fever and the symptoms are due to
plasma (liquid part of the blood) leakage through blood
vessels due to the adverse effects of the virus on the walls
of the blood vessels. This will cause thickening of blood
and circulatory failure leading to shock. Due to the same
reason, there is reduction of blood supply to essential
organs in the body, causing failure of vital organs. The
patient can die of either of these complications or by both.
Early detection and prompt treatments can prevent death’.
The reduction of platelets is not usually a reason for death
in dengue patients.
Convalescent (Recovery) phase - During
this phase, plasma ,which leaked out of the blood vessels,
will re-enter the blood stream and the patient’s condition
improves gradually. Regaining appetite and improvement of
urine output are some indicators of recovery. During this
phase too it is necessary to take adequate rest and food
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