Dengue Fever Cases In Malaysia Biology Essay

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There were only 41 cases in 1963 and the next attack of dengue only occurred in 1973 which is 1487 and it increase to 2200 in 1974. From 1975 until 1981, the cases of dengue fever are below 1000 per year but in 1982, the cases dramatically increase to 3052. After the following year, there was significance increase in 1987 with 2025 cases, 1991 with 6628 cases and 1998 with 27381 cases which was the highest cases of dengue fever in 90's. In 1999, the cases decrease but from 2000 to 2004, the cases keep increasing every year. Finally in 2005, the DF cases decrease suddenly and dramatically. The table 1.1 is not showing a definite pattern of cycle in 'rise and fall' of DF in Malaysia.

On Saturday 18 December 2010, Bernama, the news agency reported from Papar,Sabah that this year at December 17 the number of dengue cases increased from 39,597 in 2009 to 45,037. In addition the deaths also increase from 84 deaths in 2009 to 133 deaths. The city that record the highest number of dengue cases in Malaysia is Selangor which is 15,964 cases and 44 deaths. Second is Johor with 4,299 cases and 12 deaths, and Sarawak with 4,174 cases and 14 deaths. Sabah is at moderate level where the dengue cases is 2,063 cases and three deaths this year said the Health Deputy Minister Datuk Rosnah Abdul Rashid Shirlin today when launching the Karnival Mesra organised by the Papar District Hospital. However, she stressed that "But it doesn't mean we should be less concerned about ensuring its prevention". There are still places in Sabah where dengue cases are active such as Kg Pasir Putih and Kg Jawa in Tawau have two cases in each place. Taman Wira Jaya and Kg Limbungan in Tuaran also have two cases. Lastly, Kg Lipong in Beluran also active with dengue cases. (MySinchew, 2010)

How dengue fever transmitted?

Primary reservoir for dengue is human but there are nonhuman primates in Africa and Asia that act as host also. The difference between human and nonhuman host is the nonhuman host will not develop DHF but human host will develop DHF. When a mosquito feed carrier of the virus, the mosquito will acquire the virus. Thus, if the mosquito bites another host immediately, it can transmit dengue. Other than that, there is another way where viral replicate in the salivary glands of the mosquito for 8 to 12 days. 15- to 65-day of the mosquito lifespan, the mosquito will be remaining infected by the virus (Suzanne Moore Shepherd, 2009). According to Chye JK, Lim CT & Ng KB et al., dengue virus can transmit by vertical transmission also. (As cited Suzanne Moore Shepherd, 2009)

The dengue fever transmitted to human from an infected mosquito bite of the female striped Aedes mosquito mostly during probing and blood feeding. However, the signs and symptoms of dengue fever will not appear immediately. It will be in an incubation period where the dengue viruses multiply for 3 to 15 days before the signs and symptoms can appear. (Expatriate Malaysia, 2010)

There are many types of dengue viruses that can cause dengue fever. Thus, it is possible to get infected by dengue fever more than one time but it will be harsher such as dengue hemorrhagic fever. However, this cases seldom happen because there will be antibodies from the primary exposure to fight the viruses during second exposure. (Mike paddock, 2010)

Dengue viruses

Flavivirus is the genus that causes dengue fever which is with single-stranded RNA virus. There are four types of viral serotypes which are dengue virus 1 (DENV-1), dengue virus 2 (DENV-2), dengue virus 3 (DENV-3), and dengue virus 4 (DENV-4). All these are related but antigenically different and have different genotypes.

DENV is a 50-nm virus enveloped with a lipid membrane ( figure1) 

Figure 1. Dengue virus particle and microscopic picture of dengue viruses

The surface of the viral membrane consists of 180 identical copies of the envelope (E) protein which is attached by short transmembrane segment. There are several structural and non-structural mature peptides joined together to form a single large polyprotein which have about 11000 bases. The structural divided into 3 structural proteins which are capsid (C) protein, the envelope (E) glycoprotein and the membrane precursor (prM) protein. Besides, the nonstructural proteins divided into seven which are NS1, NS2a, NS2b, NS3, NS4a, NS4b and NS5. On both the 5' and 3' ends, there are short non-coding regions (Figure 2). (Dengue virus net, 2011)


Figure 2. Dengue virus genome structure with the structural and nonstructural genes

The functions of the envelope proteins are transport viral genome into the host cell, hemagglutination of erythrocytes, induction of neutralizing antibodies, and protective immune responses. When the amount of viral increase, the level of secreted NS1 (sNS1) in plasma will also increase. This NS1 involve in viral RNA replication. Thus, during secondary dengue, the level of NS1 will be in high level which is important in the formation of circulating immune complexes that cause severe dengue (Padmalal Gurugama, Pankaj Garg, Jennifer Perera, Ananda Wijewickrama, Suranjith L Seneviratne, 2010). NS3 act as a protease and a helicase, NS5 is the RNA polymerase which in charge of viral RNA replication. (Dengue virus Net, 2011)

A patient can get lifelong homotypic immunity and partial herotypic immunity when one dengue serotype infects the patient. However each people can be infected by all 4 serotypes. These dengue viruses can be transmitted through the bite of infected Aedes mosquito. The most common is Aedes aegypti which can be the highly efficient mosquito vector but other Aedes species such as Aedes albopictus also can become the vector. (Suzanne Moore Shepherd, 2009)

Symptoms of Acute Dengue fever

High fever (Health Grades Inc, 2010)

High fever may reach 105 Fahrenheit during dengue infection. Fever occurs when any pyrogens enter the human body and trigger immune system. Pyrogen is a substance that can produce fever such as virus, fungi, bacteria, drugs and toxins. The main function of hypothalamus is to keep temperature of the body to the normal level through heating mechanism, metabolism and also cooling mechanism. Thus, temperature of the body increases when pyrogens affect hypothalamus. (WebMD, Inc, 2010)

During high fever, a patient will undergo dehydration which will cause the feeling of 'burning eyes'. Normally, a patient will feel better for a full day after high fever for two to four days but the fever will return for several more days. (Steve kander, 2010)

Headache (Expatriate Malaysia, 2010)

Headache is a pain surrounding brain such as head and neck where the nerves and muscles of the head and neck sense pain. There are two categories of headache which are primary and secondary headache. Primary headache happen when medical condition not associated with the headache. If the headache associated with infections, fever, head injury or other medical condition, it is known as secondary headache. (Discovery Communications, Inc, 2010) In dengue patient, it is secondary headache because it caused by high fever.

Nausea (Expatriate Malaysia, 2010)

Nausea is a discomfort of stomach and sensation of having an urge to vomit. (David C. Dugdale, 2009)

Vomiting (Expatriate Malaysia, 2010)

The contents of the stomach forced up through the esophagus and out of the mouth. The causes could be signals from the mouth, stomach, intestine and bloodstream, which may contain infections. Thus, dengue virus infection can cause vomiting. (David C. Dugdale, 2009)

Red eyes, pain in the eyes (Expatriate Malaysia, 2010)

When the blood vessel in Conjunctiva dilated, the eyes will appear red. However, dilation of blood vessel in sclera which is known as white of the eye and episclera which is connective tissue layer between the sclera and the conjunctiva also can cause redness of the eye. Usually, fatigue, allergies and infections can cause dilation of blood vessel. Eye pain also can be caused by infection where the pain will be occurring around the eye, in the eye, or behind the eye.(Kathryn Colby, MD, PhD, 2006) Thus, dengue infections may accompanied by fatigue can cause redness and pain of the eye.

Enlarged Lymph Nodes (Expatriate Malaysia, 2010)

Lymph is the extracellular fluid that produced from the filtration of blood in human body. Lymphatic system pathways are distributed with lymph nodes where it acts as a filter for the lymph. Neck, underarm and groin are the major part of lymph nodes. Immune cells are located in these lymph nodes. Examples of the immune cells are lymphocytes, macrophages, and dendritic cells. The function of dendritic cells is to bind to the antibodies that bind to their specific antigens. This process will create a web which will be helpful to trap antigens. Degradation of the debris and extraction of material that contains antigens will be done by macrophages. Thus, both T-and B-cells that localized in lymph nodes and are exposed to this antigenic material will recognize this material. These cells will be held in the lymphoid nodes and tissues where they multiply and differentiate. If any diseases attack human such as dengue fever, these cells become effector cells and fight the disease. During this process the node will be enlarged. (Encyclopedia of Nursing & Allied Health, 2010)

Deep muscle and joint pains (Expatriate Malaysia a, 2010)

During first hour of illness, the patient can feel muscle and joint pains because when the fever increases, the skeletal muscle protein degraded. Mostly, patient with dengue fever will have complication with join and muscle pain. Therefore, the name 'breakbone fever' becomes another name for dengue fever. (, n.d.)

Thrombocytopenia (rizwansaeed, 2010)

Thrombocytopenia happen when low amount of platelet in body caused by bone marrow fail to produce platelet or platelet removed from blood in high rate. Platelets are cells in the blood that involve in coagulation process. It will aggregate each other and also to the surface of blood vessel wall when (Heather E Eaton, is damage to any part of the body. The normal level of platelet count in the circulating blood is between 150 and 400 million per milliliter of blood. The average life span of a platelet in the blood is 10 days. (Dr Claire Harrison & Professor Samuel Machin, 2006)

According to Dr Anil Handoo, 2009, mostly if thrombocytopenia occurs because bone marrow fails to produce adequate amount of platelet during dengue fever, there will be bone marrow suppression caused by dengue virus.