Common Viral Haemorrhagic Fevers include:  R R R Rift valley fever, Dengue fever, Lassa fever,.  E E E Ebola and marburg viral disease.  B B B Bovilian and argentinian haemorrhagic fever.  H H H Haemorrhagic fever with renal syndromes.

n Dengue is an arthropod-borne disease caused by any one of four closely related viruses, (Arbovirus). n Characterized by fever severe headache backache joint pains nausea and vomiting, eye pain and rash n Occasionally produces shock and hemorrhage, leading to death. Dengue fever

Epidemiology n Globally, there are an estimated 50 to 100 million cases of dengue fever (DF) and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year n Average case fatality rate of DHF is about 5% n 2.5 billion people are at risk world-wide n In the last 20 years, dengue transmission and the frequency of dengue epidemics has increased greatly in most tropical countries n It is a resurgent disease worldwide in the tropics

n Major global demographic changes (urbanization and population growth) n These demographic changes have resulted in sub-standard environmental sanitation that facilitates transmission of Ae. aegypti-borne disease; (Overcrowding in cities with poor sanitation) Factors contribute to the emergence and re- emergence of arthropod-borne diseases

n Increased travel by airplane resulting in a frequent exchange of dengue viruses and other pathogens. n Inadequate mosquito control services; the use of insecticide space sprays for adult mosquito proved ineffective approach for controlling Ae. aegypti. (Domestic habitat) n The emergence of resistance to insecticides linked to their increased misuse.

Mean Annual Number of DHF Cases Thailand, Indonesia and Vietnam, by Decade * Provisional data through 1998

Reported Cases of DHF in the Americas, * Provisional data through 1999

Distribution of suspected and confirmed Dengue fever in KSA Year N. of suspected cases N. of confirmed cases Total

Dengue Viruses n Four closely related single-stranded RNA Dengue viruses (DEN-1, DEN-2, DEN-3 and DEN-4) n Each serotype provides specific lifetime immunity, and short-term cross-immunity (A person can be infected as many as four times, once with each serotype) n All serotypes can cause severe and fatal disease

Transmission of Dengue Virus by Aedes aegypti Viremia Extrinsic incubation period DAYS Human #1Human #2 Illness Mosquito feeds / acquires virus Mosquito refeeds / transmits virus Intrinsic incubation period Illness

Replication and Transmission of Dengue Virus (Part 1) 1. Virus transmitted to human in mosquito saliva 2. Virus replicates in target organs 3. Virus infects white blood cells and lymphatic tissues 4. Virus released and circulates in blood

Replication and Transmission of Dengue Virus (Part 2) 5. Second mosquito ingests virus with blood 6. Virus replicates in mosquito midgut and other organs, infects salivary glands 7. Virus replicates in salivary glands 6 7 5

Aedes aegypti Mosquito

Aedes aegypti n Dengue transmitted by infected female Aedes aegypti mosquito n Primarily, it is a daytime feeder n Highly domesticated tropical mosquito, lives around human habitation n Lays eggs and produces larvae preferentially in artificial water containers inside and around the houses for example; plastic containers, flower vases, buckets, used automobile tires,..

Clinical Characteristics of Dengue Fever n Incubation period 3-14 days (commonly 4-7 days) n Fever n Headache n Muscle and joint pain n Nausea/vomiting n Rash n Hemorrhagic manifestations

Risk Factors Reported for DHF n Virus serotype DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and DEN-1 DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and DEN-1 n Pre-existing anti-dengue antibody previous infection previous infection maternal antibodies in infants maternal antibodies in infants n Host genetics n Age (fatal cases are among children and young adult). n Higher risk in secondary infections n Higher risk in locations with two or more serotypes circulating simultaneously at high levels (hyperendemic transmission)

Increased Probability of DHF Hyperendemicity Increased circulation of viruses Increased probability of secondary infection Increased probability of occurrence of virulent strains Increased probability of immune enhancement Increased probability of DHF Gubler & Trent, 1994

Common Misconceptions about Dengue Hemorrhagic Fever 8 Dengue + bleeding = DHF 4 Need 4 WHO criteria, capillary permeability 8 DHF kills only by hemorrhage 4 Patient dies as a result of shock 8 Poor management turns dengue into DHF 4 Poorly managed dengue can be more severe, but DHF is a distinct condition, which even well-treated patients may develop 8 DHF is a pediatric disease 4 All age groups are involved 8 DHF is a problem of low income families 4 All socioeconomic groups are affected

Treatment n Acetaminophen preparations to manage the pain and fever. n Avoid Aspirin and non-steroidal anti-inflammatory (may aggravate the bleeding tendency or cause Reyes syndrome in children). n Rest and drink plenty of fluids n Keep patient in screened sickroom or under a mosquito net n Mosquito barriers are only needed until fever subsides, to prevent Aedes aegypti mosquitoes from biting patients and acquiring virus.

Prevention n The best preventive measure is vector control n Personal protection against mosquito biting Screening doors and windows Screening doors and windows Protective clothing Protective clothing Application of mosquito repellents on exposed skin Application of mosquito repellents on exposed skin

Vector Control Methods: nBnBnBnBiological control Largely experimental Option: place fish in containers to eat larvae nEnEnEnEnvironmental control Elimination of larval habitats; Cover water holding containers, Discard artificial containers,… It is the most likely method to be effective in the long term.

Chemical Control n Larvicides may be used to kill immature aquatic stages n Ultra-low volume fumigation is ineffective against adult mosquitoes as Aedes aegypti is fully domesticated n Mosquitoes may have resistance to commercial aerosol sprays

Dengue Vaccine? n No licensed vaccine at present n Effective vaccine must be tetravalent n Field testing of an attenuated tetravalent vaccine currently underway n Effective, safe and affordable vaccine will not be available in the immediate future

Community Participation n Prevention and mosquito control through active community involvement and participation to reduce larval breeding sources is the key. n Educate the public in the basics of dengue, such as: Where the mosquito lays the eggs Where the mosquito lays the eggs The link between larvae and adult mosquitoes The link between larvae and adult mosquitoes General information about dengue transmission, symptoms and treatment General information about dengue transmission, symptoms and treatment

Patient Education n Dengue fever is NOT contagious through person-to- person contact n early hospitalization n Reduce A aegypti vector populations n Reduce exposure to A aegypti. Use insect repellent. Use insect repellent. Sleep under a mosquito net in affected areas. Sleep under a mosquito net in affected areas. Wear protective clothing. Wear protective clothing. n Vaccines NOT available

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