ABOUT DENGUE

Dengue is transmitted by the bite of an Aedes mosquito infected with any one of the four dengue viruses. It occurs in tropical and sub-tropical areas of the world. Symptoms appear 3—14 days after the infective bite. Dengue fever is a febrile illness that affects infants, young children and adults.
Symptoms range from a mild fever, to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, and rash. There are no specific antiviral medicines for dengue. It is important to maintain hydration. Use of acetylsalicylic acid (e.g. aspirin) and non steroidal anti-inflammatory drugs (e.g. Ibuprofen) is not recommended.
Dengue haemorrhagic fever (fever, abdominal pain, vomiting, bleeding) is a potentially lethal complication, affecting mainly children. Early clinical diagnosis and careful clinical management by experienced physicians and nurses increase survival of patients.

By World Health Organization

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Dengue fever infections can result in a wide range of clinical illness ranging from a nonspecific viral infections to severe and fatal haemorrhagic disease.

This 2006 photograph depicted a female Aedes aegypti mosquito while she was in the process of acquiring a blood meal from her human host. The feeding apparatus consisted of a sharp, orange-colored “fascicle” that was covered in a soft, pliant sheath called the "labellum” while not feeding. The labellum was shown here retracted as the sharp "stylets" contained within pierced the host's skin surface, thereby, allowing the insect to obtain its blood meal. The orange color of the fascicle was due to the red color of the blood as it migrated up the thin, sharp translucent tube. Note the distended abdominal exoskeleton, which being translucent, allowed the color of the ingested blood meal to be visible.

The first reported epidemics of Dengue (DF) and Dengue haemorrhagic fever (DHF) occurred in 1779-1780 in Asia, Africa, and North America. The near simultaneous occurrence of outbreaks on three continents indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more than 200 years. During most of this time, DF was considered a mild, nonfatal disease of visitors to the tropics. Generally, there were long intervals (10-40 years) between major epidemics, mainly because the introduction of a new serotype in a susceptible population occurred only if viruses and their mosquito vector, primarily the Aedes aegypti mosquito, could survive the slow transport between population centers by sailing vessels.

 

Source:www.news-medical.net/health/Dengue-Fever.aspx

Dengue Fever Symptoms

Dengue Haemorrhagic Fever is a mosquito-borne viral infection endemic in the tropical and sub-tropical regions. The female Ae.aegypti (the most important vector) mosquito is semi-domesticated, preferring to lay its eggs in man-made water containers, resting indoors and feeding in the early morning or late afternoon. There are 4 serotypes of Dengue virus. Dengue usually occurs as epidemics in Sri Lanka following monsoon seasons.
According to data from epidemiology unit of Sri Lanka, the number of total cases recorded for year 2009 is 32713. Most affected district was Kandy. Colombo, Gampaha and Kaluthara districts which have been susceptible in the past have also recorded a high rate of infection and deaths.
Dengue virus; There are 4 serotypes of the single-stranded RNA virus (flaviviridae).
Patients become infected once bitten by mosquitos. The virus passes to lymph nodes and replicates which is followed by spread to the circulation and other tissues. It is thought that infection with a secondary serotype is what leads to severe haemorrhagic disease.
Disease varies in severity
- Incubation period is 2-7 days.
- All haemorrhagic fever syndromes begin with abrupt onset of fever (39.5–41ºC) and myalgia.
- Fever is often biphasic with two peaks.
- Fever is associated with frontal or retro-orbital headache lasting 1–7 days, accompanied by generalised macular, blanching rash.
- Initial rash usually fades after 1–2 days.
- Symptoms regress for a day or two then rash reappears in maculopapular, morbilliform pattern, sparing palms and soles of feet. Fever recurs but not as high. There may be desquamation.
- DF cases experience severe bony and myalgic pain in legs, joints and lower back which may last for weeks (hence breakbone fever).
- Nausea, vomiting, cutaneous hyperaesthesia, taste disturbance and anorexia are common.
- Abdominal pain may occur and if severe suggests DHF pattern.The signs of dengue fever/ Dengue haemorrhagic fever are- High fever, rash, hypotension and narrow pulse pressure, poor capillary refill.
- There may be hepatomegaly and lymphadenopathy.
- A tourniquet placed on an arm may induce petechiae in early DHF cases. DHF sufferers exhibit a bleeding tendency as evidenced by petechiae, purpura, epistaxis, gum bleeding, GI haemorrhage and menorrhagia. There may be pleural effusion, ascites and pericarditis due to plasma leakage.
- Petechiae are best visualised in the axillae.
- Flushing of head and neck.
- Tender muscles on palpation.
- Periorbital oedema and proteinuria may be present.
- Maculopathy and retinal haemorrhages may also occur.
- DSS pattern cases progress through DHF until profound shock due to severe hypotension is present.
- CNS involvement e.g. encephalopathy, coma, convulsions.

- Hepatic failure: Means failure of the liver
- Encephalopathy: Means damage to the brain causing fits, loss of consciousness and confusion- Myocarditis – Inflamation of heart muscles
- Disseminated intravascular coagulation - Damage to blood vessels and blood cells causing problematic bleeding and clottingDengue can cause death
- FBC - low platelets and high packed cell volume if haemoconcentrated. Usually white cell count will fall
- Infection may be confirmed by isolation of virus in serum and detection of IgM and IgG antibodies for Dengue by ELISA, monoclonal antibody or haemagglutination
- Molecular diagnostic methods such as reverse-transcriptase-PCR are increasingly being used.
- Chest X-ray may show pleural effusion.
- Bed rest
- Nutritious diet and lot of liquids, But avoid red and brown foods and drinks like coffee, chocolate, grapes etc as it may misinterpret vomiting as blood stained vomitus.
- Fever control with paracetamol, tepid sponging and fans. Aspirin should be avoided.
- Need to seek advice from a qualified medical practitioner if fever lasts for more than 2 days
- Hospital managemnt includes intravenous fluid resuscitation with close monitoring. Haemorrhage and shock will require Fresh Frozen Plasma, platelets and blood. Intensive management with inotropes of the shock syndrome may be required in severe DHF/DSS cases.
- Vaccines are being researched
- Anti-mosquito public health measures such as reducing breeding sites ( flower pots, fish tanks,tires, coconut shells, tins, water collecting plants, gutters which can collect water) and good sewage management
- Insecticides to destroy the larvae
- Mosquito nets can be used during day time as the Aedes mosquitoes is day-biting.
- Mosquita repellents
- There is a bacteria called Bacillus thuringiensis which destroy the mosquito larvea

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