Dengue alert
Q: A newspaper article I read last week noted the alarming increase in dengue cases in Metro-Manila during the first few months of this year. Do you think dengue will be a bigger problem in the Philippines this year than the previous years? Can you please write on the precautions we need to take to prevent dengue. --Noli R., Marikina City
A: The Department of Health (DOH) has indeed recently reported that the incidence of dengue in Metro-Manila during the first quarter of 2011 has more than doubled compared to the same period last year (4,399 cases in 2011 versus 1,984 in 2010). Likewise, in the Ilocos, the number of dengue cases increased from 226 to 788 cases while in Central Luzon the number of cases increased from 632 cases to 2,630 cases. However, the number of dengue cases nationwide went down by 4.32 percent (i.e., from 15,493 cases last year to 14,837 dengue this year).
There is a good chance the number of dengue cases in the Philippines this year will surpass last year’s total because this year, the rainy season, which is peak season for dengue, promises to be longer and wetter than last year.
Dengue or dengue fever is caused by a virus that is transmitted to humans by at least two species of the Aedes mosquito, Aedes aegypti and Aedes albopictus. In the Philippines, the main vector is Aedes aegypti —a small black mosquito that has white stripes on its back and legs.
When an Aedes mosquito bites and feeds on the blood of a person with dengue, it acquires the dengue virus. The virus proliferates within the mosquito and after eight to eleven days, the mosquito becomes infective to humans and remains so for the rest of its life, which can be anywhere from 15-65 days. When an infective mosquito bites a human, it inadvertently injects the dengue virus into the person. Incidentally, only the female Aedes mosquito bites and it does so because animal blood is needed for proper development of its eggs. Also, the female dengue mosquito loves to bite during the day and has a flight range of up to 300 meters.
Female Aedes mosquitoes lay their eggs (hundreds at a time) in pools of stagnant water, which during the rainy season could be found in flower vases, jars, pots, bottles, drums, roof gutters, drains, old tires, tree cavities, plant stumps, etc. After about a week, the eggs hatch into larvae or wrigglers, which transform into pupae in another week before becoming adult mosquitoes after one to two more days. By the way, if the pool dries up before the eggs hatch, the eggs stay viable up to a year and promptly hatch when the rains come.
Usually, dengue is a mild, self-limiting febrile illness, but some cases progress to the severe and sometimes fatal form of the illness known as hemorrhagic fever or H-fever, which is characterized by bleeding that usually involves the gastrointestinal tract, skin and the nervous system, and that typically starts when the fever has already subsided.
Dengue can be prevented by controlling its mosquito vector or protecting people from mosquito bites. Measures to control the mosquito are most effective if they are done on a community basis.
• Screen your house. Alternately you can use mosquito nets, mosquito repellants, mosquito coils (“katol”) and mats, and mosquito patches that one sticks on his/her outer clothing.
• Isolate persons with dengue fever in a screened room for at least 5 days from the onset of symptoms.
• Eliminate all possible breeding places of mosquitoes in your neighborhood. Fill potholes; cover water containers and septic tanks; do 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; cut tall grass, etc. -Article courtesy of Manila Bulletin.
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