Dengue fever

M.FAHD-UN-NABI KHANX-OUSMAN PUBLIC SCHOOL

Dengue is a mosquito-borne infection that in recent decades has become a major international public health concern. Dengue is found in tropical and sub-tropical regions around the world, predominantly in urban and semi-urban areas.

The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. South-east Asia and the Western Pacific are the most seriously affected.

The incidence of dengue has grown dramatically around the world in recent decades. Some 2.5 billion people – two fifths of the world's population – are now at risk from dengue. WHO currently estimates there may be 50 million dengue infections worldwide every year.

An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children. About 2.5% of those affected die.

You can get dengue virus infections from the bite of an infected Aedes mosquito.

Mosquitoes become infected when they bite infected humans, and later transmit infection to other people they bite.

Dengue is not contagious from person to person.

Derived from one of the plagues (yellow fever)

Different species : yellow fever, St. Louis encephalitis, Japanese encephalitis, west Nile encephalitis, Dengue fever

Nuclei acid – non segmented (+)polarity Flavivirus nucleotide sequence is same to picornaviridae Size: 40 - 60nm Virion: Spheroid

Typical uncomplicated (classic)

Fever within 4 to 7 days after you have been bitten by an infected mosquito and include :

Severe headache Severe joint and muscle pain Nausea and vomiting Rash (The rash may appear over most of your body 3 to 4

days after the fever begins, and then subsides after 1 to 2 days )

Fever, constant headaches, severe dizziness and loss of appetite.

• Dengue hemorrhagic fever (can cause death )

• A potentially lethal complication, affecting mainly children • Includes all of the symptoms of classic dengue plus :

• Bleeding from the nose, gums, or under the skin, causing purplish bruises

Dengue shock syndrome (the most severe form of dengue disease)

Includes all of the symptoms of classic dengue and dengue hemorrhagic fever, plus

Massive bleeding Shock (very low blood pressure)

This form of the disease usually occurs in children (sometimes adults) experiencing their second dengue infection. It is sometimes fatal, especially in children and young adults.

The dengue rash is characteristically bright red “petechiae” and usually appears first on the lower limbs and the chest; in some patients, it spreads to cover most of the body.

Petechiae are tiny little broken capillary blood vessels.

Blood tests - thrombocytopenia and relative leukopenia - low platelet and white blood cell count

The diagnosis of dengue is usually made clinically. The classic picture is high fever with no localizing source of infection, a petechial rash, vomiting blood, or bloody diarrhea.

Tourniquet test

Close monitoring of vital signs in critical period (between day 2 to day 7 of fever) is vital. Increased oral fluid intake is recommended to prevent dehydration.

A platelet transfusion is indicated in rare cases if the platelet level drops significantly or if there is significant bleeding. The presence of melena may indicate internal gastrointestinal bleeding requiring platelet and/or red blood cell transfusion.

Patients may receive paracetamol preparations to deal with these symptoms if dengue is suspected (people with dengue fever is advised not to take aspirin).

The best way to prevent dengue virus infection is to take special precautions to avoid being bitten by mosquitoes. Several dengue vaccines are being developed, but none is likely to be licensed by the Food and Drug Administration in the next few years.

Because Aedes mosquitoes usually bite during the day, be sure to take precautions, especially during early morning hours before daybreak and in the late afternoon before dark.

Get rid of areas where mosquitoes breed (stagnant water).