Does fogging work?
No, it will not work.
In the long term control of dengue at least.
We have been fogging all our life. It is a well-known symptom of dengue. You can diagnose dengue from one kilometre away – by seeing the wafting fog filling up the air in your neighbourhood. It is so well known that people have become oblivious with fogging that they thought cigarette smoke can repel mosquitoes. Smoking is unhealthy. Fogging may save lives.
Despite the special effects that comes from your neighbourhood friendly fog men that look like Van Halen and Metallica making a theatrical entrance with a loud guitar roar and artificial smoke, the impact of fogging may not last, as you would, reminiscing the lingering effect of your first ever rock concert! For some, seeing the fog men at work create a false sense of security that whatever is causing the disease is under control.
Let us see some of the reasons why we should not depend too much on fogging.
Fogging only kills the adult mosquitoes.
Yes, it does kill the adult mosquitoes and bring down their numbers. You would sense an unusually quiet night when you do not have to roll up the newspapers hitting yourself like a mad man trying to kill the little vampires.
But that is only temporary.
Although the adult mosquitoes are killed, the young ones – the larvae, are protected from the insecticide laden fog, only waiting for a few more days to emerge into adult mosquitoes and replace their dead comrades.
Fogging does not kill the larvae.
To kill the baby mosquitoes – the larvae, fogging is not the answer. As a reminder, all standing clean water, indoors and outdoors, needs to be removed. Bodies of clean water are perfect for the growth of the larvae.
In situations when you cannot remove the water collection, such as an aquarium, bath and potting plants, adding abate into the water can help kill the larvae and prevent the mosquito from reaching a complete cycle. This is your only license to kill.
You can easily buy abate from your local pharmacy. If the salesperson does not know what abate is, just tell them “ubat bunuh jentik” or any of your favourite local parlance, to get one.
You are not at home when the fog men came.
The adult mosquitoes are actively looking for food at dusk and dawn. Therefore, fogging is done at those times have a high chance of killing the mosquitoes.
Since mosquitoes are also active indoors, the fog men must fog indoors too. They can’t fog indoors if no one is at home to let them in. The adult mosquitoes that may be resting indoors may be spared.
You would not let the fog men in when they come.
With a spate of incidents resulting in harm, injuries and even kidnapping, homeowners find it difficult to allow strangers to come into their house.
It is your right to not allow them in for fear of your safety.
But men carrying the heavy fogging machine all bundled up in protective gear bearing the ministry of health emblem – you could not be wrong to identify them as genuine health personnel doing their jobs – preventing other people from getting dengue.
Some pointers to note, the affected neighbourhood will be informed earlier of fogging activities through flyers or announcement. If you are still not sure, you can always call the local health office to verify.
You are afraid that the fog can kill both the mosquitoes and you.
“No, we can’t let you in, our cat will die once you start spraying,” One lady cat lover blurted behind the security grilles of her home. Please lady, people are dying!
There are some issues regarding the effect of pesticides used on human during fogging. The concentration of pesticides used is lethal to the mosquitoes but it is not enough to even kill a pet rabbit or cat.
In addition, fogging is a targeted and limited activity. The chemicals used are also biodegradable by sunlight. It cannot accumulate over time and cause toxicity.
On the other hand, with the low concentration of pesticides, we fear that fogging alonemay not be effective.
It is expensive to fog and maintain the fogging machine.
Machines, like cars, need maintenance after a certain mileage. Maintenance may be overlooked when the fogging machines are overused in outbreak situations.
The nozzles of the fog machine may be clogged with dirt. As a result, the fogs are merely white thick smoke, creating a few coughs in the neighbourhood, leaving the mosquitoes unharmed.
Lack of staff, the lack of machines and too many outbreak sites to be covered.
With such limitations, fogging cannot be done efficiently if there are many outbreak areas to be controlled.
Fogging is not just spraying “smoke” in a vicinity. There are techniques involved. Besides the concentration of the pesticides, the nozzle width, the speed of fogmen, the swing techniques, the wind direction etc. are all important in killing more mosquitoes.
The high number of outbreaks inundated our workers that in a recent report, only 40% of houses were fogged within 5 days after the first case was reported. This is below par, as the target set is 85%.
Where do we go from here?
Fogging is effective as the first blow to stop a possible dengue outbreak. Blow for blow, like a tired boxer, the fire power of fogging will reduce over time. It is not sustainable.
Other sources of energy will be needed to sustain the boxer. Gatorade, hair blowing motivation during intervals and the cheering crowd will spur him on to emerge the eventual winner. Same goes for dengue.
Fogging is not the answer. Source reduction is. It needs to begin in the community. Nothing high tech – just common sense – keeping clean, dispose of all items that can collect water and we are all heading to a dengue free Malaysia.
Dr. Helmy Hazmi is a community medicine specialist with a major in Epidemiology and Biostatistics. He is currently working in his hometown, Kuching, as a medical lecturer. Find out more in The Team page.