Dengue fever is currently increasing in Bangladesh. It’s a viral disease carried by the Aedes mosquito. Symptoms of dengue fever usually appear within three to fifteen days of transmission of the virus through the bite of an Aedes mosquito. Dengue patients usually recover within two to seven days. In some cases, the disease can take a severe hemorrhagic form called dengue hemorrhagic fever. This results in bleeding, decreased blood platelet levels, and secretion of blood plasma. 

Dengue shock syndrome sometimes occurs in some cases. Blood pressure drops dangerously in dengue shock syndrome. Several species of Aedes mosquito are the main carriers of dengue virus, of which Aedes aegypti is the most important. There are five serotypes of the virus. Infection with one serotype of the virus results in lifelong immunity to that serotype, but temporary immunity to a different serotype. Later, if the patient is infected with a different serotype of dengue virus, severe complications may occur. 

WHO has identified dengue as one of the twenty neglected tropical diseases. People infected with dengue virus are usually asymptomatic or have mild symptoms like common fever. In a small proportion it is fatal. The time between the onset of symptoms and the initial stage of the disease lasts 3-14 days, but in most cases it is 4-7 days. Therefore, affected area-returned tourists may not have dengue if fever and other symptoms start 14 days after returning home. Children often have symptoms, such as the common cold, vomiting and diarrhea, and symptoms are generally less severe than adults.

Symptoms of dengue include sudden onset of fever, headache, joint pain, and rash. Pain in the spine and back is the special symptom of this disease. The course of infection is divided into three stages: primary, acute and convalescent. In the initial stage there is high fever, accompanied by general aches and headache. It usually lasts two to seven days. At this stage, 50-80% of the symptoms are rash. A red rash appears on the first or second day of symptoms, or a measles-like rash later in the illness.

Some small red dots that do not disappear when pressed on the skin due to broken blood vessels, may appear in this area, and some may also have minor bleeding from the mucous membranes of the mouth and nose. In some people, the illness becomes extreme, causing a high fever that usually lasts one to two days. During this stage, due to increased capillary absorption and leakage, a large amount of fluid accumulates in the chest and abdominal cavity. 

This results in reduced fluid in the bloodstream and reduced blood supply to vital organs. At this stage there is deformity of organs and profuse bleeding. Dengue shock syndrome and dengue hemorrhagic fever occur in less than 5% of dengue cases, but those with prior infection or secondary infection with other dengue virus stereotypes are at increased risk. Dengue fever virus is an RNA virus. Other members of the same genus include yellow fever virus, West Nile virus, St. Louis encephalitis virus, Japanese encephalitis virus, tick-borne encephalitis virus, Kyasanur forest disease virus, and Omsk hemorrhagic fever virus, most of which are arthropod or insect-borne and are therefore called Arbovirus. 

Humans are the primary carriers of this virus, but non-human primates are also transmitted. A single bite can cause infection. The female mosquito becomes infected by feeding on the blood of a dengue victim and carrying the virus in its stomach. After about 8-10 days, the virus spreads to other cells in the mosquito's body, including the mosquito's salivary glands, and finally to its saliva. Although infected for life, this virus has no harmful effect on mosquitoes. "Aedes aegypti" prefers to lay eggs in artificial reservoirs, live in close proximity to humans and feed on human blood more than other vertebrates.

The disease is more prevalent in infants and young children. Dengue can be fatal in people with chronic illnesses such as diabetes and asthma. When a mosquito carrying the dengue virus bites someone, the virus enters the skin through the mosquito's saliva. It enters in white blood cells, and the virus continues to reproduce inside the cells as they travel throughout the body. In response, white blood cells produce a number of signaling proteins such as interferon, which are responsible for many symptoms, such as fever, flu, and severe pain.

In severe infections, the production of the virus inside the body increases, many organs can be affected, and fluid from the bloodstream seeps through the walls of small blood vessels into the body. As a result, less blood circulates in the blood vessels and the blood pressure drops so much that the necessary organs cannot get enough blood. In addition, bone marrow dysfunction also reduces the number of platelets, which are essential for effective blood clotting. This increases the chance of bleeding which is one of the major problems of dengue fever.

Prevention depends on control of infected mosquitoes and protection from their bites. The World Health Organization recommends an integrated one-pronged control program with five basic guidelines: (1) advocacy, social activism, and legislation to strengthen public health organizations and communities, (2) collaboration between public and private health and other departments, (3) optimal use of disease resources, (4) evidence-based decision-making to ensure that any intervention is properly targeted, and (5) capacity-building to respond adequately at the local level.

The primary method of controlling mosquito is to destroy its growth environment. Control can also be achieved by emptying water containers or by applying insecticides or biological control agents at these sites, although spraying with organophosphates or pyrethroids is not considered very cost effective. Keeping in mind the adverse health effects of pesticides and the cost of control agents, reducing waterlogging through environmental treatment is the best control method. 

People can avoid mosquito bites by wearing full-body clothing, using mosquito nets when resting, or applying insect repellent chemicals. Between 1960 and 2020, the incidence of dengue increased by 30 percent. Reasons for this increase are thought to be urbanization, population growth, increased international travel and global warming. The expansion of villages, towns and cities in epidemic-prone areas and the increased movement of people in recent decades are responsible for the growth of epidemics and the spread of viruses.

Avoiding Aedes mosquito bites is the main way to prevent dengue. Therefore, mosquito breeding should be prevented by destroying the habitat of mosquitoes. For this, it is necessary to remove the water trapped in various containers suitable for breeding of Aedes mosquitoes, such as cups, tubs, tires, can shells, pits, roofs, etc. Clothing that covers most of the body should be worn. If anyone have dengue fever, should take full rest and drink more fluids. Paracetamol can be given to reduce fever. Often the patient may need to be given intravenous saline and in severe cases the patient may need to be given blood. Antibiotics and non-steroidal anti-inflammatory drugs should not be taken in case of dengue, as the risk of bleeding increases.

Writer: Columnist, and Asst Officer, Career & Professional Development Services Department (CPDS), Southeast University.

Citizentimes/OH/MY