Tue | Jun 18, 2019

Michael Abrahams | The dengue virus and its vector

Published:Monday | January 14, 2019 | 6:23 AM
Abrahams

It’s official. We are now in the midst of a dengue outbreak. Like chikungunya and Zika, dengue fever is a mosquito-borne tropical disease caused by a virus. Unlike chikungunya and Zika, however, dengue is endemic to Jamaica. In other words, it is always lurking around on our island.

There are four types, known as serotypes, of the virus that causes dengue: DEN-1, DEN-2, DEN-3, DEN-4. Infection occurs when one is bitten by a female mosquito, usually Aedes aegypti, carrying the virus. The mosquito becomes infected when it sucks the blood of a person afflicted with the virus, and after about a week, the mosquito can then transmit the virus to another person. 

An infected mosquito is capable of transmitting the virus for the rest of its life, which is usually two weeks to a month. The critters can fly up to 500 metres seeking out water-filled containers to lay their eggs, but usually remain close to human habitats. The Aedes aegypti mosquito lives in urban areas and breeds mostly in man-made containers, such as cups, bottles, cans, barrels, drums and discarded tyres.

The eggs hatch when in contact with water and can withstand very dry conditions and survive for months. Female mosquitoes lay dozens of eggs up to five times during their lifetime.

Unlike many other mosquitoes, this species is a daytime feeder, with its peak biting periods being early in the morning and in the evening before dusk. At these times, it will bite multiple people, making it a highly efficient epidemic vector mosquito. In-between feeding periods, adult mosquitoes usually rest indoors in dark areas such as closets, under beds and behind curtains, where they are protected from wind, rain and most predators.

Symptoms, which usually begin four to six days after infection, may include:

· Sudden, high fever.

· Severe headaches.

· Pain behind the eyes.

· Severe joint and muscle pain (hence the term ‘breakbone fever’).

· Fatigue.

· Nausea.

· Vomiting.

· Skin rash, which appears two to five days after the onset of fever.

A variant of dengue, known as severe or haemorrhagic dengue, can also occur. Symptoms in these cases include: 

· Severe abdominal pain.

· Persistent vomiting.

· Bleeding gums.

· Vomiting blood.

· Rapid breathing.

· Fatigue.

· Restlessness.

If you suspect you have dengue, seek medical attention. In the meantime, it is safe to take paracetamol (panadol, Tylenol, cetamol) to ease the discomfort of pain and fever. Do NOT take aspirin or painkillers known as non-steroidal anti-inflammatory drugs (NSAIDS).

Common examples are diclofenac (Cataflam, Voltaren) and ibuprofen (Motrin, Advil). These drugs are usually useful in the management of pain and fever, but in dengue, they may increase the risk of bleeding, especially in the severe, haemorrhagic form, with disastrous consequences. Rest and hydration are important to achieve recovery from the infection. 

Rather than having to treat this malady, it is preferable to prevent it. Knowing the breeding and feeding habits of the vector helps us in this regard. So, do as much as you can to decrease breeding options. Do not allow stagnant water to remain uncovered in and around your homes, communities, workplaces and schools. Tour these areas regularly and discard water from open containers, or if the water is to be used, cover the receptacles securely.

If you wish to use open containers in which water has gathered, scrub them after emptying them to get rid of eggs which may have already been laid. Regularly change the water in outdoor bird baths and pets' water dishes.

Protecting yourselves with repellents containing DEET, IR3535 or Icaridinis recommended, in addition to wearing long-sleeved clothing when possible, especially during the main biting periods. Mosquito nets and screens, insecticides, mosquito coils and vaporisers are also useful. If you are already infected, these methods should also be employed in order to protect those around you. 

If you have recovered from dengue, do not get complacent. The virus has four types, and while infection with one type usually gives lifelong immunity to that type, it only provides short-term immunity to the others. As a matter of fact, unfortunately, subsequent infection with a different type increases the risk of severe complications. So continuous vigilance is advised. 

Dengue is rarely fatal, but the pain and incapacitation from it can be severe. In order to restrict the spread of the infection, control of its insect vector is critical. In other words: “If yu nuh waan pop dung and fenkeh-fenkeh,  yu fi bun mosquito an’ run weh dengue.”        

For more information, check out the Ministry of Health’s website at https://www.moh.gov.jm/.

- Michael Abrahams is a gynaecologist and obstetrician, comedian and poet. Email feedback to columns@gleanerjm.com and michabe_1999@hotmail.com, or tweet @mikeyabrahams.