Dengue the might of Aedes or the debility of humans | Page 2 | Sunday Observer

Dengue the might of Aedes or the debility of humans

It is just one bite. Slightly irritating perhaps, falling at zero level of the Schmidt Sting Pain Index if one would want to measure it against. The gain, just three millionth of a litre of blood. But, the effect! We, Sri Lankans felt it strongly last year (2017) the numbers affected tripling by end of the year, from that of 55,150 the previous (2016). Sri Lankan war against Dengue has a history close to that of the civil war which ravaged the country for three decades.

Just two years shy, battles were won, quite a few. Internationally acclaimed protocol and information management; reduction of the mortality (death) rate; improved and regular vector control systems throughout the country; improved treatment facilities in high risk areas and enhanced follow up procedure to name some. However, last year Aedes had much gain in the battlefield. One hundred and eighty five thousand six hundred and eighty eight (185,688) were struck. Was it the might of Aedes or the debility of humans?

As we step into year 2018, Dengue Fever (DF) and Dengue Haemorrhagic Fever (DHF) continue to be a major public health problem. So far this year, it had affected 6,429. Last year (2017) saw the highest number of dengue cases in the medical annals of Sri Lanka. However, doctors managed to keep the number of deaths low. There were less than 3 deaths per 1,000 people affected; an achievement to their credit.

What is Dengue Fever?

Considering the acute infectious diseases transmitted by mosquitoes there is “no other disease at present as complex as dengue”, says Dr. Hasitha Tissera, National Dengue Control Unit (NDCU). It has a sudden onset and a great majority has a stereotypic clear outcome. Mildly affected they recover without any problem. However, for a minority the disease would affect with severe outcomes. The challenge is to differentiate those who have a severe outcome. As this needs to happen at early stages of the illness (by 72 hours or 3 days) to reduce complications and manage the disease, it is always better to get professional medical help and not self-medicate, Dr. Tissera advises.

“We recommend anyone having fever for more than 2 days to go for a medical check-up by a practitioner and a full blood count (FBC). That is a must.” One can inform the doctor that he or she had had fever and ask whether he/she should get an FBC.

“Although we talk of one illness, these are 2 diseases,” explains Dr. Tissera. One with a very clear outcome (dengue fever DF), the other unless you treat properly you will have complications (dengue haemorrhagic fever DHF) and will require stringent attention by a specialist. However, both these stages have specific known features. DHF though initially have features similar to that of DF, with time it displays more distinct features.

According to Dr. Tissera, the Full Blood Count (FBC) test would help the clinician to determine the severity of the illness. Antigen test (NS1), if necessary could be done with the recommendation of the clinician.

However, it is not an absolute requirement, as it is a syndromic disease (with a set of signs and symptoms that appear together characterizing the disease). “Even if the antigen test is negative, if the person has these secondary features we still want to manage him/her as a dengue patient.” However, a patient’s treatment depends on the FBC and therefore is a must.

When one is suffering from DHF, at its early stages of 3-4 days the plasma starts leaking out from the blood vessels to the interior cavity. As a result the blood thickens and consequently the heart finds it difficult to pump. The heart rate increases, sometimes even the patient feels it. Without treatment at this stage, when a critical amount of blood is devoid of the plasma even the blood pressure drops and the patient suffers from Dengue Shock Syndrome (DSS). A patient at DSS stage is in critical condition.

Time is of essence and treatment should be immediate. At this stage the heart’s inability to pump blood to the vital organs result in organ failure.

It affects the liver, kidneys, the heart and the lungs. Consequently, all the body functions de-arrange. For example, when the blood clotting mechanism doesn’t work properly, there could be profuse bleeding.

Neglect and delay in treatment would result in death.

The reason some people fail to recognize features such as lifelessness and fainting, consequent to the heart’s inability to pump blood is because they feel comfortable when they lie flat for some time. “As long as you lie flat you can’t feel it but when you get up your heart has to put more effort and you fail faintness.

This is the dengue shock syndrome where you are in a critical condition. Time is of essence. If the treatment is not given immediately you might lose your life. ”

Identification of the early signs enables saving life if one has DHF. Early treatment prevents the evolution of the disease to a complicated stage whereas neglect and delay takes a patient to a moribund state, a place of no return where recovery would be a miracle.

In DSS, if left more than 10 hours untreated death is inevitable.

Infants, elderly, obese persons, pregnant women and those having underlying diseases should be more cautious when suffering from fever. They should seek medical advice early.

Another downside of dengue is that the infection is caused by four dengue virus strains or serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). Therefore, one could be infected a number of times. Though once affected, a person gets natural lifetime immunity – that is only for the particular viral strain/serotype. He or she could get infected by other strains later on.

DHF is more prevalent in these repeated infections. “DHF is more sinister in those who have been infected before. The first infection is usually very subdued sometimes mild or just DF. It is the second attack with a different type, which is significant,” stresses Dr. Tissera “Therefore, protect yourself from mosquito bites and getting re-infected”.

How does it spread?

Dengue cannot spread from person to person. As any other vector borne disease, the virus has to go through a phase inside the body of a host – in this case, Aedes aegypti and Aedes albopictus two mosquitoes that carry the virus. When a female mosquito bites a human with a sufficient amount of viral load in blood, it gets affected.

The virus multiplies inside the mosquito’s body. The next time it bites another human, is transmits the virus to that person. Aedes aegypti is identified as the main carrier of dengue virus in Sri Lanka. A. aegipti hosts more than the dengue virus in its 3mm body. Commonly known as the yellow fever mosquito it spreads the same. In addition it hosts Chikungunya virus and Zika virus. Aedes albopictus, a similar looking but larger (10mm) mosquito known as the Asian tiger mosquito is also identified as another vector contributing to the spread of dengue in the country.

It is a highly adaptive mosquito species preferring human blood though they feed on a variety of mammals, birds, reptiles and amphibians. It is known to spread chikungunya virus as well as dengue.

Both A. aegypti and A. albopictus have short flight ranges of about 200m. They are found closer to human habitats mostly within 100m. A. aegypti is a day biter and a container breeder found indoors.

A female mosquito could lay between 500 to 1,000 eggs during its 3-4 week lifetime. Recent research had revealed that A. albopictus, previously known as an outdoor biter also could be found indoors, displaying feeding and breeding patterns previously associated with A. aegypti .

When a human gets an infected mosquito bite, it takes an incubation period between 3 to 10 days before the onset of fever. There is a high viral load in the blood during the first 24 hours. Dengue (DHF) has 3 phases, a fever phase usually of 2-3 days, a critical phase lasting 2 days (and less for children) and a recovery phase of 2-5 days.

How is dengue infection treated? A sudden onset of a “very high fever (40°C/104°F) which doesn’t respond to paracetamol,” should itself be a concern, opines Dr. Eranga Narangoda, Consultant Physician, National Institute of Infectious Diseases (NIID). The hospital (NIID), with a total of 190 beds had catered to a daily deluge of over 450 patients during July 2017, at the peak of the epidemic. Admissions were far less in January. “Nevertheless, all stakeholders need to be vigilant,” he emphasizes.

A patient admitted to a hospital, “undergoes monitoring and symptomatic treatment to manage the disease and to prevent it from progressing to the critical stage or shock,” explains Dr. Narangoda.

At the hospital a patient’s vital signs (heart rate and blood pressure), his/her general condition, the amount of fluid intake against the urine output and the blood viscosity is monitored regularly.

Twice a day, ultra sound scanning is done. Intra-venous fluids and blood is administered as necessary. It is crucial to regulate the fluid intake as “too much of fluid worsens the condition. So is neglect, taking strong painkillers and alternative medication.” They not only deteriorate the condition but “might cause liver damage, and the main reason for severe bacterial infections afterwards and the primary cause for deaths due to the disease,” he emphasizes.

Dr. Narangoda urges the general public to “seek medical advice on the first day itself. Go to a qualified doctor or the outpatient department of the nearest hospital.

If you suspect DHF get admitted at a hospital where there is a consultant physician.” Government hospitals offer the FBC test, sentinel hospitals throughout the country offer DHF treatment.

He also advises those who are at risk such as pregnant women, elderly (above 70) and those with chronic illnesses such as diabetes, kidney, liver and heart related diseases to seek immediate medical assistance.

What can we do to eradicate dengue fever?

The spread of dengue, is an eye opener as to how socially responsible we Sri Lankans are. The more socially responsible a community is the less vulnerable it is to the spread of dengue.

Along with vector control activities by relevant authorities, preventing mosquito bites at two crucial points – biting a patient within 24 hours of the onset of fever and biting a non-infected person could play a major role in reducing the infection rate. An outdoor environment where garbage disposal is carried out safely and responsibly eliminates vector breeding grounds.

Socially responsible behaviour cannot be forced through fines or other law enforcement methods. It needs to be inculcated.

Therefore, unless we change our attitudes and behaviour, and make ‘responsibility’ our battle cry, Aedes and dengue will have an inevitable victory. 

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