Once bitten, twice shy

January 08, 2016 12:00 am | Updated September 22, 2016 10:48 pm IST

What are the indirect health impacts of climate systems? A look at mosquito-borne diseases like dengue.

Dengue is an awful disease. Let me share my experience.

Day 0: A feeling of being not-quite-well. A little vulnerable - as though my body's defences were on the verge of being overwhelmed. My shoulders hurt and my head ached.

Day 1: The fever started off at 103F - not a promising start. My skin was flushed and my palms were an unfamiliar, angry red. My body felt like it had been run over by a truck and as for my headache - I can remember it with a shudder 6 years later. A heavy dose of painkillers pushed me into an uneasy sleep.

Day 2: The fever reached 104.5F. The pain continued unabated. I was mildly delirious. My platelet count had dropped substantially. It was too soon for the tests to appear positive for dengue, but to be safe, my mother, a paediatrician, was keeping me well hydrated and was on the watch for the disease progressing into the more deadly, Dengue Hemorrhagic Fever. I remember the cavernous sensation of pain which formed a veil between me and the reality around.

Day 3: The fever broke. Too weak and with a knee and calf pain that were continuously acute, I slept.

Day 4: The fever returned, sharply. There is no treatment for dengue, only supportive therapy, that consists mainly of giving as much fluids as possible to the patient and being watchful. Any deterioration of the condition means that the patient will require a (careful) infusion of "fluids".

Day 5: The fever started coming down and with it the veil shrouding me from reality began to lift.

The pain continued in my knees for several more weeks, but I had beaten the disease. I was fortunate.

So why talk about dengue?

Because dengue incidence has skyrocketed in India. Dengue is caused by a virus carried within an Aedes mosquito. The mosquito is infected by the virus when it sucks blood from a person infected with the virus. The mosquito then bites another person continuing the cycle of infection. Mosquitoes like warm, moist climates and breed in pools of water. Infections peak during and after a rainy spell.

What does this have to do with climate change?

Let us look at the two main signs of climate change and see how they impact this disease:

First, temperature. An increase in temperature has several ways of increasing Dengue prevalence: it increases the length of the dengue infectious season, it increases the geographic spread of Dengue, it allows for the virus to reproduce faster within the mosquito, shortens the incubation period and lastly allows for the mosquito to survive better which increases its chances of biting (and infecting) more people. Also, a very hot atmosphere weakens our immune system making us easier prey to the disease.

Next, the alternating flood-drought scenario that comes along with climate change causes water to stagnate (made worse by rubbish clogging drains) forming ideal breeding grounds for mosquitoes. Also, water shortages in cities cause people to store water in containers - this also increases the breeding sites for mosquitoes.

So, while further modelling studies are required to understand precisely by how much dengue will go up in India in the coming decades due to a warming climate, we can safely say: it will go up by a lot.

That's not a pleasant thought.

So, what can we do?

First, the news of a vaccine recently released in Mexico is a very positive thing. Perhaps our domestic vaccine manufacturers can also join the race to make a cheap, effective vaccine.

Two, Water management needs to be put on a war footing. India has successfully managed her coal problems and laying out roads faster than predicted. We need to see that happens with water too.

Three, given that Dengue is going to become much more prevalent, we cannot hide from the problem. Singapore reported 11265 cases of Dengue in 2015. Compare this with the 90040 reported cases in India in 2015 with 200 times the population of Singapore and a much dirtier environment. This suggests rampant under-reporting - a fact confirmed off-the-record by most doctors.

Let us acknowledge there is a problem. Let us consider the possibility that it may get a lot worse. We can then begin to deal with it.

(Climaction is a fortnightly column that is published in MetroPlus Weekend on alternate Fridays. The views expressed in the articles are those of the author.)

The next article in this series will appear on January 22, 2016.

Feedback and questions may be e-mailed to climaction2015@gmail.com

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