Dengue

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DR. EDUARDO G GONZALES
Last July 28, the Department of Education (DepEd) raised an alert against
dengue hemorrhagic fever, but their press release on the matter contained
very few details on the disease itself. For information of the public can you
discuss dengue in your column, especially on how to prevent it? — Maria M.,
Malabon City

The Department of Education (DepEd) has indeed issued an alert against dengue
hemorrhagic fever last July 28, as part of its efforts to protect the populace from the
disease following the release of a Weekly Disease Surveillance Report from the
Department of Health (DoH), which showed that dengue remains number two on the
list of the most prevalent diseases in the Philippines.
In its memorandum, the DepEd directed all school administrators to mobilize school
health personnel to disseminate information on the prevention and control of
dengue.

Dengue fever is a mosquito-borne disease that is endemic in the Philippines. It
occurs year-round but its incidence is higher during the rainy season because its
mosquito vector is able to breed more rapidly during this period. Annually, dengue
fever affects thousands of Filipinos, mostly children, and accounts for dozens of
deaths.

Dengue fever is caused by any of four strains (1, 2, 3 and 4) of the dengue virus.
The virus is transmitted to humans by the Aedes mosquito; it is not capable of
human to human transmission. At least two species of this mosquito, Aedes aegypti
and Aedes albopictus, serve as vector of the virus. In the Philippines, the main
vector is Aedes aegypti.

The Aedes mosquito is a small mosquito (3-4 mm long, minus the legs). It is black
but it has white dots on its back and head regions and white stripes on its legs. Only
the female mosquito bites and it does so because animal blood is needed for proper
development of its eggs. The dengue mosquito, which prefers human blood over
blood of other animals, loves to bite during the day, but it also bites at night.

The mosquito acquires the dengue virus when it bites a person with dengue fever.
The virus proliferates inside, but otherwise does not harm, the mosquito. Later, the
viruses find their way and stay in the salivary glands of the mosquito.

Eight to 11 days after biting an infected human, the mosquito becomes infective and
remains so for the rest of its life, which lasts from 15-65 days. When it bites a
human, an infective mosquito unknowingly injects the dengue virus into the person.
The female Aedes mosquito breeds in stagnant water. It lays up to a hundred eggs
at a time, in every possible place where non-running water exists: flower vases, jars,
pots, bottles, drums, roof gutters, drains, old tires, tree cavities, plant stumps, etc.
The eggs hatch into larvae (wrigglers) about a week after being laid. Another week
later, the larvae transform into pupae, which become adult mosquitoes in another
one to three days. By the way, the embryonated eggs can withstand dry conditions
for up to a year then promptly hatch when the rains come.

The signs and symptoms of dengue fever appear three to 15 days after the bite of an
infective mosquito. They include moderate to high grade fever that lasts for five to
seven days, headache, loss of appetite, abdominal pain, joint and muscle pains, pain
around the eye area, and a skin rash.

Dengue fever is usually a mild, self-limiting illness, but the pattern of presentation of
the disease has apparently changed. Cases of the severe form of the illness, known
as dengue hemorrhagic fever (H-fever) are on the upsurge. Typically, in H fever,
bleeding that usually involves the gastrointestinal tract, skin and nervous system
occurs when the fever has already subsided.

Immunization is arguably the best way to prevent dengue. A vaccine against the
virus has already been developed and is reportedly already in use in Thailand, but it
is not being used in the Philippines yet.

Even without a vaccine, dengue fever can be prevented by eliminating all possible
breeding places of its mosquito vector. Within their neighborhood (note: the flight
range of the Aedes mosquito rarely exceeds 100 meters) people must: fill potholes,
cover water containers and septic tanks; not allow empty cans, soft drink bottles,
spare tires, etc. to accumulate water; ensure that drains and gutters are not clogged
and that water flows freely in sewage lines; and, dispose garbage properly and
regularly.

Additionally, people should protect themselves from mosquitos by: screening their
house or using mosquito nets, mosquito repellants and/or mosquito coils ("katol")
and mats. Likewise, persons with dengue fever should be isolated in a screened
room for at least five days from the onset of the symptoms.
Address inquiries on health matters to Dr. Eduardo G. Gonzales, DLSU College of
Medicine, Dasmariñas, Cavite 4114.

SOURCE: Manila Bulletin

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