_ Ghanashym Sharma , MPH student ,
Northern University of Bangladesh,
Dengue haemoragic fever (DHF) as a major public health problem
The first reported epidemics of DF occurred in 1779 to 1780 in Asia, Africa and North America. Thee near simultaneous occurrence of outbreak on the three continuous indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more the n 200 years. During most of the this time , DF Was considered a mild, nonfatal there were long intervals (16-40 years) between majors epidemics, mainly because the introduction of a new serotypes in a susceptible population occurred only if viruses and their mosquito vector could survive the slow transport between population centers by sailing vessels.
A pandemic of dengue began in South East Asia after Second World War has spread around the globe sine then. Epidemics caused by multiple serotypes (hyperendemicity) are more frequent , geographic distribution of dengue viruses and their mosquito vectors has expanded, and DHF first appeared in the 1950, but by 1975 it had become a frequent cause of hospitalization and death among children in many countries in that region.
Dengue [DEN-ghee] is a flu-like viral disease spread by the bite of infected mosquitoes. belongs to flavivirus genus which is a member of the flaviviridae family. They are human pathogens that cause large epidemics and tens thousands deaths annually in many parts of the world. Dengue hemorrhagic fever is a severe, often fatal, complication of dengue.
There is no specific treatment for dengue.
Prevention centers on avoiding mosquito bites in areas where dengue occurs or might occur and eliminating breeding sites.
Dengue viruses occur in most tropical areas of the world. Dengue is common in Africa, Asia, the Pacific, Australia, and the Americas. It is widespread in the Caribbean basin. Dengue is most common in cities but can be found in rural areas. It is rarely found in mountainous areas above 4,000 feet.
The mosquitoes that transmit dengue live among humans and breed in discarded tires, flower pots, old oil drums, and water storage containers close to human dwellings. Unlike the mosquitoes that cause malaria, dengue mosquitoes bite during the day.
All types of dengue virus are re-emerging worldwide and causing larger and more frequent epidemics, especially in cities in the tropics.
Several factors are contributing to the resurgence of dengue fever:
No effective mosquito control efforts are underway in most countries with dengue.
Public health systems to detect and control epidemics are deteriorating around the world.
Rapid growth of cities in tropical countries has led to overcrowding, urban decay, and substandard sanitation, allowing more mosquitoes to live closer to more people.
The increase in non-biodegradable plastic packaging and discarded tires is creating new breeding sites for mosquitoes.
Increased jet air travel is helping people infected with dengue viruses to move easily from city to city.
Dengue hemorrhagic fever is also on the rise. Persons who have been infected with one or more forms of dengue virus are at greater risk for the more severe disease. With the increase in all types of virus, the occurrence of dengue hemorrhagic fever becomes more likely.
Dengue fever & Dengue hemorrhagic fever
Dengue fever is a flu-like illness spread by the bite of an infected mosquito.
Dengue hemorrhagic fever is a severe, often fatal, complication of dengue fever. The mortality rate in DHF is 10-40% (Mostly children)
Infectious agent
Dengue and dengue hemorrhagic fever are caused by any of the dengue family of viruses. Dengue viras serotypes DEN-1, DEN-2, DEN-3, DEN-4 cause Dengue (DEN) and dengue haemorhagic fever (DHF). Infection with one virus does not protect a person against infection with another.
Transmission
Dengue is spread by the bite of an Aides mosquito. Principally Aedes aegypti (day bitting mosquito found in urban areas, preferring to feed on humans). The mosquito transmits the disease by biting an infected person and then biting someone else.
Signs and symptoms
Dengue fever usually starts suddenly with a high fever, rash, severe headache, pain behind the eyes, and muscle and joint pain. The severity of the joint pain has given dengue the name "break bone fever." Nausea, vomiting, and loss of appetite are common. A rash usually appears 3 to 4 days after the start of the fever. The illness can last up to 10 days, but complete recovery can take as long as a month. older children and adults are usually sicker than young children.
Most dengue infections result in relatively mild illness, but some can progress to dengue hemorrhagic fever. With dengue hemorrhagic fever, the blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Bruising can be a sign of bleeding inside the body. Without prompt treatment, the blood vessels can collapse, causing shock (dengue shock syndrome). Dengue hemorrhagic fever is fatal in about 5 percent of cases, mostly among children and young adults.
Latent Period
The time between the bite of a mosquito carrying dengue virus and the start of symptoms averages 4 to 6 days, with a range of 3 to 14 days. An infected person cannot spread the infection to other persons but can be a source of dengue virus for mosquitoes for about 6 days.
Diagnosis
Dengue is diagnosed by a blood test.:
Laboratory test which can be helpful in diagnosing DEN /DHF and monitoring the progress of patients being treated for DHF and DSS include.
1. Measurement of haematocrit
In DHF there is a rise in haematocrit level (often by 20% or more) indicating haemo-concentration due to increased vascular permeability and leakage of plasma.
2. Platelet Count
This is greatly reduced (below 100? 109 /L) in DHF.S
3. White cell count and differential
The white cell count is variable leucopania is common and blood film may show reactive lymphocytes.
4. Coagulation tests
In DHF, Bleeding and Clotting times are prolonged and the prothrombin time and partial thromboplastin times are increase. Fibrinogen level is usually decreased.
5. Clinical Chemistry tests
In DHF, serum aminotransferases and blood urea are raised. Serum Sodium and albumin are reduced. Albuminuria is usually present and in some patients also haematuria. Measurement of electrolytes is helpful is monitoring treatment.
Risk for dengue
Anyone who is bitten by an infected mosquito can get dengue fever. Risk factors for dengue hemorrhagic fever include a person's age and immune status, as well as the type of infecting virus. Persons who were previously infected with one or more types of dengue virus are thought to be at greater risk for developing dengue hemorrhagic fever if infected again.
Prevalence
In tropical countries around the world, dengue is one of the most common viral diseases spread to humans by mosquitoes. Tens of millions of cases of dengue fever and up to hundreds of thousands of cases of dengue hemorrhagic fever occur each year.
Treatment
There is no vaccine and specific treatment for dengue. Persons with dengue fever should rest and drink plenty of fluids. They should be kept away from mosquitoes for the protection of others. Dengue hemorrhagic fever is treated by replacing lost fluids. Some patients need transfusions to control bleeding.
Prevention and control
- Avoiding mosquito bites when traveling to areas where dengue occurs.
- Avoid mosquito bites when traveling in tropical areas:
- Use mosquito repellents on skin and clothing.
- When outdoors during times that mosquitoes are biting, wear long-sleeved shirts and long pants tucked into socks.
- Avoid heavily populated residential areas.
- When indoors, stay in air-conditioned or screened areas. Use bed nets if sleeping areas are not screened or air-conditioned.
- If you have symptoms of dengue, report your travel history to your doctor.
- Eliminate mosquito breeding sites in areas where dengue might occur:
- Eliminate mosquito breeding sites around homes. Discard items that can collect rain or run-off water, especially old tires.
- Regularly change the water in outdoor bird baths and pet and animal water containers.
Reference:
- www.Searo.who.int/en/section10/section 3322.htm
- www.cdc.gov/neidod/avdid/dengue/.
- www. nebi.nlm.nih.gov/entrez/
- www.ete-online.com/content/2/1/1
- Cheesbrough.M, District Laboratory practice in tropical countries, Part-2, Cambridge University press, page no 248, 249.
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