by Henrylito D. Tacio
RAINY season is here again and dengue fever is just waiting to find its new victim. “Mosquito-borne diseases like dengue fever usually break out during the rainy season, particularly after a flood or strong rain,” said the Department of Health (DOH). “This is because pools and puddles of water formed after the rain are ideal breeding places for the day-biting female mosquito that carries the disease.”
The regional office of the World Health Organization (WHO) said that peak incidence for dengue cases in most Asian countries is from June to November each year. “Generally, high cases of dengue are recorded in all endemic areas during the rainy season,” the Manila-based agency adds.
Today, dengue is the most common mosquito-borne viral disease of human beings. Just recently, “it has become a major international public health concern,” to quote the words of the United Nations health agency. Globally, 2.5 billion people live in areas where dengue viruses can be transmitted.
When dengue fever attacks
Most people infected with dengue viruses have dengue fever. Here’s what happens: Patients suddenly develop a high fever. They also may have a headache around their eyes or at their forehead. A rash, which usually appears 24-48 hours after the fever starts, begins at the trunk and then develops on the arms and legs. Patients experience muscle aches and severe bone pain (this is the reason why it is sometimes called as “breakbone fever”). Two-to-six days later, nausea and vomiting may take place.
The fever usually lasts three to nine days and then goes away. One to two days after the fever goes away a second rash appears. This rash disappears in one to five days and is accompanied by a slight fever (also known as “saddleback fever”).
But what concern most health officials is the lethal complication called dengue hemorrhagic fever (DHF). Here, the patient experiences fever, headache, loss of appetite, vomiting, cough, and feel very tired. This lasts 2-5 days. Afterwards, he will feel cold and have clammy hands and feet. Other symptoms include: a flushed face, sweating a lot, very restless and irritable. Oftentimes, the patient will have little red spots on the forehead, arms, and legs. Usually the person gets better in 2-3 days.
However, others don’t. And this is where the trouble starts. The blood pressure of the patient goes down and he may develop what medical experts called as dengue shock syndrome. “After a dengue patient has gone into shock, it is just a matter of time before multi-organ failure occurs and death becomes inevitable,” says Dr. Dominic Garcia, an infectious disease specialist.
Children more at risk
According to health officials, deaths occur in 5-40% of children that develop shock. “Survival of these children is directly related to quickly getting them to a hospital and intensive care being given to the person,” Dr. Garcia pinpoints.
In the Philippines, majority of dengue patients are children. A study conducted by the health department in 1991 pointed out that majority of the patients are between the ages 5 and 9 years old. “It is a big problem among children because it a major causes of illness and deaths,” says Dr. Lulu Bravo, a professor of the College of Medicine at the University of the Philippines.
However, the risk of drying is higher among teenagers. “This is a common observation and maybe it’s related to the fact that DHF has a more severe illness with bleeding and shock after an initial infection,” explains Dr. Bravo. “The appearance of a second infection triggers a more severe reaction and high response of antibodies. Thus, minor illnesses are expected during the first encounter usually in the younger age group.”
According to Dr Bravo, death is due to the body fluids leaving the blood vessels and accumulates in body cavities or spacing, thus causing shock. It may also be due to severe bleeding either internally into the intestines, in the brain, or in other organs of the body. “The outcome could be fatal within hours of severe bleeding or in many cases children are pulled out of shock by adequate management of fluids and blood or blood products replacement,” the UP professor says.
Dengue viruses are transmitted to humans through the bite of infected ‘Aedes aegypti’ mosquito. Also known as tiger mosquito, because of its peculiar white stripes, this species is quite small, measuring only five millimeters. It is attracted to the odor and sweat of human beings and bites only during daytime. However, its peak biting time is after sunrise and at dusk – especially one hour before sunset.
Dr. Michael MacDonald, an American entomologist from Johns Hopkins University in Baltimore, said that dengue is not directly transmitted from one person to person. “Once infected, a mosquito remains infective for life, transmitting the virus to susceptible individuals during probing and blood feeding,” he points out.
According to Dr. Garcia, when a person is bitten and the dengue virus is deposited in the bloodstream, it usually takes an incubation period of four to six days before symptoms appear.
Medical science has identified four strains of dengue viruses – all of which can cause dengue fever. However, if there is infection with a second strain in a patient who has had dengue fever caused by another strain previously, this person is likely to develop DHF. The exact reason is for this not clear, but medical science believes that antibodies produced after the first infection enhances the subsequent infection related complement activation.
On the other hand, if more than one strain causes the disease, DHF will occur too. Not all people who develop sequential infections get DHF. Again, the reason is not clear. Dr Scott Halstead, of the Health Sciences Division of New York-based Rockefeller Foundation suggests that if antibodies are of neutralizing type, they do not enhance the growth of subsequent dengue viral infection. However, if there are no neutralizing antibodies, the other antibodies enhance the viral replication. But the question still remains: Why do some people develop neutralizing antibodies and others do not?
No treatment yet
Until now, there is still no specific treatment for dengue fever. “There is no antiviral or antibiotic that can directly fight off the dengue virus,” Dr. Garcia said. “All that the physician can do is to give supportive treatment such as antifever pills (like paracetamol) and plenty of fluids (orally and intravenously.” Aspirin should not be given to any patient with fever as a home remedy because it can further aggravate bleeding
Doctors urged people who caught the dengue virus to be admitted to the hospital. In this way, the blood pressure and blood count can be monitored and in case of complications doctors can immediately make the necessary precautions.
Explains Dr. Eric Tayag, one of the country’s dengue experts: “DHF results in plasma leakage and disorders in haemostasis (the clotting mechanism in blood). When plasma leaks out the circulating blood volume is slowly depleted. This is accompanied by abnormalities in the clotting mechanism that results in bleeding. Thus, fluid accumulates within the body and affected organs like the liver or brain begin to bleed.
“Death is due to the body fluids leaving the blood vessels and accumulates in body cavities or spaces thus causing shock,” explains Dr. Bravo. “In some instances, the death is also due to severe bleeding either internally into the intestines, in the brain, or in other organs of our body.”
What community can do
During dengue outbreaks, fogging or spraying is done in schools and areas where there is an epidemic. “Fogging and using chemicals will only give people an illusory sense of security,” explains Dr. Tayag. After all, the insecticide used in fogging only kills the adult mosquito while leaving millions of larvae untouched. In addition, mosquitoes not killed may develop resistance to the insecticide.
The community should work together in curbing dengue epidemic. “The community should be educated on factors causing dengue because its cooperation is vital to its control,” commented an official the communicable disease control service of the health department.
Dr. Tayag concludes, “While government has an important role in dengue control, many still deny that it is really the families and communities which have the greater responsibility for dengue control. Everybody looks up to government to provide the solutions. But really, those mosquitoes breed in our homes. More often and unknowingly, we provide the breeding places for these mosquitoes. Thus, while government reminds, the people should mind.” – ###