Dengue: An added concern amidst the pandemic
a year ago
The number of dengue cases are on the rise, with the ongoing rainy season nurturing breeding grounds for mosquitoes. According to official data, over 24,160 dengue cases have been reported so far for this year. With the high population density, the Western Province acts as a dengue hub in the country, while cases are also being reported in almost all districts. Generally, dengue has a seasonal transmission in Sri Lanka with the peaks occurring in parallel to the monsoons. Amidst the Covid-19 pandemic, dengue is creating a double whammy. National Dengue Control Unit Disaster Management Focal Point Medical Officer Dr. Lahiru Kodituwakku shared wisdom on this matter. Following are the excerpts of the interview. What is dengue and why should we be worried about it? Dengue is a vector (mosquito)-borne viral infection spread across the globe, particularly in tropical and subtropical countries. It is estimated that about half of the world population is at risk now. According to statistics from the World Health Organisation (WHO), there are around 100-400 million dengue infections each year. It causes considerable mortality as well. Some researchers suggest that severe forms of dengue can cause up to 21,000 deaths per year around the world. The situation is not so different in Sri Lanka. We are hyperendemic to dengue, meaning there are persistent, high levels of infections within the country. As of 17 November 2021, there were 24,633 suspected dengue cases reported from Sri Lanka. Apart from Covid-19 infection, this is the biggest public health challenge we encounter in the country. Also, it is a very complex disease. It has a wide spectrum, ranging from asymptomatic (people who have the disease yet show no symptoms) to severe forms such as dengue haemorrhagic fever (DHF), which is responsible for the majority of deaths due to dengue. The dengue virus has four distinct yet closely related serotypes as well. Although infection from one serotype can give you lifelong immunity against that particular serotype, cross-immunity (immunity against other serotypes) is thought to be partial. This means that you can be infected four times within your lifespan by the different dengue viral serotypes. Secondary infection (being infected from a different serotype than the first) is considered to be comparatively severe as well. So really, we should be worried. Where do outbreaks of dengue occur, both globally and within the country? Although found across the world, 70% of the actual disease burden is found in Asia. Given the favourable weather conditions for the two major vectors – Aedes aegypti and Aedes albopictus – to breed, Southeast Asia accounts for a substantial proportion of the disease burden in Asia. Frequent outbreaks are found in Indonesia, Thailand, Myanmar, Sri Lanka, and Timo-Leste, considered as “Category I” countries by WHO, denoting that cyclical epidemics can occur in urban centres and the disease is spreading to rural areas in these countries. In Sri Lanka, dengue outbreaks or peaks in dengue cases usually coincide with two monsoons, southwestern monsoon from May to September and north-eastern monsoon from December to February. There is distinct geographical variation too. During the southwestern monsoon, we experience an increase in dengue cases in the Western, Southern, Central, Sabaragamuwa, and North Western Provinces. However, during the north-eastern monsoon, we observe a spike in cases mainly within the Northern and Eastern Provinces. Yet, lately, there have been notable changes in this distinct pattern too. According to statistics, the Western Province bears the brunt of dengue cases – usually around 50% of total cases in Sri Lanka. Furthermore, the Colombo District, particularly the Colombo Municipal Council (CMC) area, is considered to be a hotspot for dengue infections. In 2017, Sri Lanka experienced by far the biggest outbreak in history, with nearly 180,000 patients and 440 deaths. Currently, we are experiencing outbreaks in some of the high-risk medical officer of health (MOH) divisions of CMC Colombo as well as the Gampaha, Kalutara, Kurunegala, and Badulla Districts. Is it contagious from person to person? How does it spread? Dengue is transmitted to humans through bites of an infected female Aedes mosquito. After, mosquito feeds on an infected person, the virus replicates within the mosquito’s gut and reaches its salivary gland – this extrinsic incubation period, as it is called, takes around eight to 12 days. This transmission can occur from individuals who are viraemic (persons having the virus in blood) to dengue (including asymptomatic, pre-symptomatic, and symptomatic individuals) and most are viraemic up to four to five days. Once this infected mosquito bites a healthy individual, it can pass on the virus to that healthy individual. This is called the “mosquito to human transmission”. Although primary transmission of dengue is through mosquito vectors, there is evidence in literature that maternal transmission (from a pregnant mother to her baby) can occur. However, it is thought to be linked to the timing of dengue infection during pregnancy. What are the signs and symptoms of dengue fever and the severe form of dengue? Dengue fever, a comparatively milder form of the infection, could be characterised by high-grade fever of two to seven days’ duration, retro-orbital pain (pain behind the eyes), arthralgia (joint pain), myalgia (muscle pain), headache, nausea, vomiting, and rash. Due to the debilitating nature of body aches associated with dengue, it is often called “breakbone fever”. What the public should be extra cautious about is the warning symptoms of dengue, indicating severe forms called DHF and dengue shock syndrome (DSS). These warning symptoms can be a severe stomach ache, persistent vomiting, bleeding from gums, bleeding with stools and unusual vaginal bleeding, blood in vomitus, or blood in urine. If you observe fatigue, drowsiness, irritability, restlessness in your child with fever, or if he or she persistently refuses to eat or drink, you should be heading to a hospital at that moment. Reduced urine volume or not passing urine at all are symptoms that you should be really worried about. In dengue fever, symptoms usually last for two to seven days, and in DHF, the patient enters into the “critical phase” about three days after the onset of fever. At this time, one might notice a drop in fever, and the warning symptoms mentioned above can be manifested. How do you investigate to confirm the disease? There are several ways of investigating the disease. If you have high fever for 24 hours, you can do a blood test for dengue NS/antigen. The most suitable time to do this test is within 18 to 30 hours of the onset of fever, where the test has the highest probability of identifying a dengue infection. However, sensitivity (identifying ill people as ill) of the test gradually decreases with time. The other important fact you should remember is that even though the test turns out to be negative, there still is a chance that you might be harbouring dengue. Therefore, it is essential to correlate your history of exposure and clinical symptoms with the test result as well. For that, you should be heading to your family doctor or the nearest hospital. Secondly, if you have a fever for 48 hours, you can perform a full blood count (FBC). Doctors would be able to come to a decision on your diagnosis by observing the decrease in your white blood cell count and platelet count. The packed cell volume (PCV) in your FBC would be helpful in the management of dengue as well. You will be asked to do repeated FBC by your doctor, and do not forget to show the reports again, even though you see a gradual rise in your platelet and white cell counts. It is important to a doctor to consider your investigation findings in the context of your clinical condition to come to a definitive diagnosis. So, if you have two investigative findings and two of the clinical features with fever for a duration of two to seven days, doctors would highly suspect that you are having dengue. This is called “Fever +2+2” criteria in dengue, which is widely used for dengue surveillance and identifying suspected dengue patients from hospitals. Thirdly, you can also do a dengue antibody test to confirm a dengue infection. This test can be performed after five days of onset of fever. Usually, a positive IgG test denotes a previous infection, whereas a positive IgM test denotes a current dengue infection. There are advanced diagnostic tests such as the dengue RT-PCR test, which is rarely used in public domain and used only for research purposes. Is there any treatment for dengue? There are certain medicines which are said to increase the platelet count. Are these medicines effective in the treatment? There is no definitive treatment for dengue. You will be given paracetamol in the correct dose and duration to control the fever, along with other fever controlling measures such as tepid sponging. It is important to note that you should not take any over-the-counter painkillers (non-steroidal anti-inflammatory drugs [NSAIDs]) such as ibuprofen, diclofenac sodium, or mefenamic acid for fever control in dengue. Such ill practices could make you vulnerable to severe complications of dengue, including internal bleeding that can end up in deaths. Moreover, steroids such as dexamethasone and prednisolone, which are being used for treatment of chronic conditions such as asthma and joint disease, should not be taken without medical advice. If you are on long-term use of these drugs and are simultaneously having dengue, you should consult a qualified doctor as soon as possible. It is important to have adequate rest and the correct amount of fluids to keep yourself hydrated. Once you reach hospital for the treatment of dengue, health staff will carefully measure your fluid intake and urine output, measure your vitals (pulse, blood pressure) to identify any clinical deterioration, and make sure you are fever-free. If in any case they identify that you are suffering from DHF, they will observe you under a strict regime and put you under different investigations, including daily ultrasound scans, to detect any fluid leakage into your internal cavities. It is the balancing of your fluids that will ultimately decide your fate in dengue; therefore, early identification of the disease and early admission to a hospital where such expertise is available is a must. There is a misconception among the public that a mere rise in the platelet count is a sign of cure in dengue. A rise in the platelet count is one of the investigative parameters among many others; doctors would carefully consider any signs of improvement. Hence, relying on medications that are said to increase the platelet count or any other household remedies would further complicate the problem and are especially dangerous in case of DHF and other severe forms of dengue. If you are suspecting dengue, your priority should be seeking medical help as early as possible. Can an individual get infected with dengue two or more times? Yes. As described earlier, you can be infected from either of the four serotypes once in your lifetime. Primary infection from one serotype would give you immunity only for that serotype but provides no or partial immunity against other serotypes. Research suggests that secondary infection would be comparatively severe than the primary infection. What are the habitats of the mosquito, and are there certain times which this mosquito is active? Both dengue vectors are container breeders, meaning they breed in a wide variety of natural or artificial containers, mostly with dark-coloured surfaces, that comprise clear, unpolluted water. If you consider our households, breeding places could be found both inside and outside. Refrigerator trays, flowerpots, ant traps, and non-functional cisterns/toilets are common breeding sites inside the home. Roof gutters, discarded household items exposed to rain, uncovered overhead tanks, and thrown away items such as food containers, polythene/plastic wrappings, pet feeding cups, and ornamental ponds are common breeders outside the home. Further, breeding places can be found at ground level as well as above the ground level; for example, receptacles and water collection spots on slabs. When you consider the major breeding sites, construction sites, religious places, and educational institutions including schools are found to be most at risk. Aedes aegypti is a very competent vector. It is an “anthropophilic vector”, meaning a female mosquito tends to feed on multiple people for a blood meal. Dengue breeders are day bitters as well. Morning peak biting hours fall between 6 a.m. and 11 a.m., while in the evening, it is between 3 p.m. and 5 p.m. The danger is, during these peak biting hours, most of the schoolchildren and workers are exposed to mosquitos due to their outdoor activities. What is the responsibility of the public to prevent dengue? The prime responsibility of the public is to make their individual and collective environments free of dengue breeding places. This includes your home, office or workplace, your child’s school, and places of worship. Since a tiny amount of water is sufficient to facilitate dengue breeding, attending to places where water can collect is essential. We expect four basic good practices from the public: (i) Remove discarded receptacles, (ii) close the lids of containers, (iii) clean the surfaces of water collecting items, and (iv) store them in such a way that water cannot be collected. Secondly, apply a suitable mosquito repellent to exposed areas of your body or wear garments that cover your body when you go out. You can look for the approved list of repellents in the official website of the National Dengue Control Unit (www.dengue.health.gov.lk). Thirdly, seek medical help as soon as possible when you have a fever. Especially at a time where different viruses including Covid-19 are circulating, it is difficult to distinguish between initial clinical symptoms of these viral diseases. You should seek professional help instead of waiting at home. Last but not least, educate your child on these good practices, and spread the message on prevention among your friends and loved ones, because only a conscious and collective effort from all of us can get us through this age-old public health problem.