Epidemiology, Prevention & Control of Dengue Fever / DHF Dr. Dilip Kumar Das

Dengue Syndrome: The Problem Most common arthropod-borne viral disease Important emerging disease of the tropical and sub-tropical regions Predominantly in urban and semi-urban areas Globally 2.5 - 3 billion people live in areas having active dengue transmission Estimated 50 million dengue infections occur every year

Geographical Distribution Africa Southeast Asia (including India) China Middle East Caribbean Central and South America Australia South and Central Pacific 110 countries are endemic for dengue

Category of SEAR Countries Category A: Indonesia, Myanmar, Thailand Category B: India, Bangladesh, Maldives, Sri Lanka Category C: Bhutan, Nepal Category D: DPR Korea

India, Bangladesh, Maldives & Sri Lanka : Category B Dengue Status DHF an emerging disease Cyclical epidemics becoming more frequent Multiple virus serotypes circulating Expanding geographically within the country Aedes aegypti principal epidemic vector Role of Aedes albopictus uncertain

Dengue Reporting States in India Andhra pradesh Bihar Chandigarh Delhi Goa Gujarat Haryana Karnataka Kerala Maharashtra Sikkim Punjab Rajasthan Tamil Nadu Pondicherry Uttar Pradesh Dadra & Nagar Haveli West Bengal

Dengue is spreading Certain states had dengue for long and are regularly reporting cases with cyclical peaks New states are reporting Dengue Overall the toll of dengue is increasing every year 30 states are reporting dengue 450 million people are at risk

Agent: Dengue Virus Is an arbovirus - Genus flavivirus Composed of single-stranded RNA Has 4 serotypes (DEN-1, 2, 3, 4) All 4 serotypes are in circulation in India Transmitted by female Aedes mosquitoes Infection with one serotype confers lifelong immunity

Host Infects humans and several species of lower primates Humans main reservoir of virus Transmission cycle: ‘Man-Mosquito-Man’ All ages and both sexes are susceptible Clinical features vary according to the age of the patient Deaths are more in children during DHF outbreak

Vectors of Dengue Aedes aegypti - principal vector Aedes albopictus- limited role in transmission Aedes aegypti wide spread in tropical and sub-tropical countries Lives around human habitation (Aedes aegypti mainly in domestic urban areas and Aedes albopictus in peri-domestic rural and near forest areas) 3

Mosquito density fluctuates with rainfall and water storage practices Breeding habit: Vectors breed in several types of unused / discarded artificial containers Biting habit: Predominantly bites during the daytime and prefers for human blood Resting habit: Aedes aegypti is indoor rester and Aedes albopictus mainly outdoor rester Mosquito density fluctuates with rainfall and water storage practices 3

Transmission of Dengue Virus by Aedes aegypti Mosquito feeds / Mosquito refeeds / acquires virus transmits virus Extrinsic incubation period Intrinsic incubation period Viremia Viremia Illness Illness 8 12 16 20 24 5 28 DAYS Human #1 Human #2 5

Replication and Transmission 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 3 4 1 2 6

Replication and Transmission 6 7 5 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 7

Dengue Transmission Pattern Epidemic dengue - single viral strain introduced in a region - sufficient susceptible hosts & adequate vectors: explosive transmission Hyper endemic dengue - continuous circulation of multiple virus serotype - large pool of susceptible hosts and competent vectors constantly present - adults are generally immune - travelers are at more risk

Dengue – Clinical Presentation Asymptomatic Symptomatic Undifferentiated fever Dengue Fever (DF) Dengue Haemorrhagic Fever (DHF) Dengue Shock Syndrome (DSS)

Undifferentiated Fever Presents like other viral fevers Infants, young children and some adults are infected for the first time Maculopapular rash may be present Can not be differentiated from other viral infections

Dengue Fever Fever: An acute febrile illness of 2-7 days duration with two or more of the following manifestations Headache Retro-orbital pain Myalgia Arthralgia Rash Hemorrhagic manifestations Leucopenia 18

Dengue Haemorrhagic Fever The following must all be present :  Fever, history of acute fever, lasting for 2-7 days, occasionally biphasic. Haemorrhagic tendencies, evidenced by at least one of the following – A positive tourniquet test  Petechiae, ecchymoses or purpura  Bleeding from the mucosa, gastrointestinal tract, injections sites or other locations  Haematemesis or melaena Thrombocytopenia (100000 cells per mm3 or less)

DHF criteria… Evidence of plasma leakage due to increased vascular permeability, manifested by at least one of the following – A rise in average haematocrit for age and sex > 20 % A > 20 % drop in the haematocrit following volume replacement treatment compared to baseline Signs of plasma leakage (pleural effusion, ascites and hypoproteinaemia)

Four Grades of DHF Grade 1 Fever and nonspecific constitutional symptoms Positive tourniquet test is the only hemorrhagic manifestation Grade 2 Grade 1 manifestations + spontaneous bleeding Grade 3 Circulatory failure manifested by rapid and weak pulse, narrow pulse pressure (< 20 mm Hg), hypotension, cold clammy skin and restlessness Grade 4 Profound shock (undetectable pulse and BP) 23

Dengue Shock Syndrome - Rapid and weak pulse, and All the 4 criteria of DHF must be present, plus evidence of circulatory failure manifested by : - Rapid and weak pulse, and - Narrow pulse pressure (< 20 mm Hg) or - Hypotension for age and - Cold clammy skin and restlessness.

Course of dengue illness: 3 phases Febrile phase Critical phase Recovery phase

Danger Signs in Dengue Minute spots on the skin suggesting bleeding within the skin Nose and/or gum bleeding Abdominal pain or passage of black and tanned stool Refusal to take food or drink Abnormal behaviour or drowsiness Difficulty in breathing or cold hands and feet Reduced amount of urine being passed 24

Laboratory Diagnosis of DF/DHF Isolation of the dengue virus from serum, plasma, leucocytes or autopsy samples Demonstration of virus antigen or RNA: - Demonstration in autopsy tissue or in serum samples - Detection of viral genomic sequences in autopsy tissue, serum or CSF by PCR Serological Diagnosis: - Detection of IgM antibodies: 5 days after symptoms - Detection of IgG antibodies: A fourfold or greater increase in IgG titre in paired serum samples taken at an interval of 10-14 days confirms the diagnosis

Prevention and Control of Dengue/DHF No drug or vaccine available against dengue infection Vector control is the only method of choice Early detection and use of standard case management guidelines help in reducing mortality substantially Dengue fever/DHF surveillance

Dengue/DHF Surveillance Surveillance is essential for: Monitoring dengue situation in an area Early detection of an impending outbreak Timely preventive and control measures Surveillance should include: - Epidemiological surveillance - Entomological (Vector) surveillance - Laboratory based surveillance

Epidemiological Surveillance Use of standard case definitions Organization of surveillance network - Routine reporting - Sentinel reporting - Outbreak investigations Detecting early warning signals Effective and efficient response mechanism

Entomological (Vector) Surveillance Continuous process in endemic areas Adult and Larval Surveillance: pre-monsoon, monsoon and post-monsoon period to generate data for early warning signals for dengue outbreak Entomological indices - House Index - Container Index - Breteau Index

Laboratory Based Surveillance Isolation of the dengue virus Demonstration of virus antigen Serological Diagnosis - Detection of IgM antibodies - Detection of IgG antibodies

Early Warning Signals in Dengue/DHF Outbreaks Sudden increase in reporting of suspected cases with clustering in time and space Enhanced vector density as indicated through house index/container index/breteau index with reference to vector mosquito Detection of viral activity either in vector or man

Management of Dengue Case Early reporting of the suspected cases Management is primarily symptomatic & supportive

Management of DF Bed rest during acute febrile phase Antipyretics (Paracetamol) or sponging Analgesics or mild sedatives - No aspirin should be given Oral fluids and electrolyte therapy No role of antibiotics or platelet transfusion Should be monitored till afebrile and platelet count and hematocrits are normal

Management of DHF Hospitalisation: Rise in haematocrit of > 20 %, platelet count of 50000/ mm3 or less, spontaneous haemorrhage, signs and symptoms of shock, oliguria and circum-oral cyanosis Antipyretics Plenty of oral fluids Volume replacement by IV fluids Serial haematocrit levels and frequent assessment of vital signs e.g. urine output

Management of DSS Immediate administration of IV fluids to expand plasma volume Electrolyte levels and blood gases should be determined periodically and corrected Oxygen therapy in shock/hypotension Blood transfusion in case with significant haemorrhage Fresh frozen plasma/concentrated platelets in DIC

WHO guidelines for treatment Patients divided into 3 broad groups Group A: Uncompleted disease Group B: Patients for in-hospital management Group C: Requiring emergency treatment and referral

Vector Control Measures Personal Prophylactic Measures Use of mosquito repellent creams, liquids, coils, mats etc. Wearing of full sleeve shirts and full pants with socks Use of bed nets for sleeping infants and young children during day time

Biological Control Chemical Control Use of chemical larvicides like abate in big breeding containers Aerosol space spray during day time Biological Control Use of larvivorous fishes in ornamental tanks, fountains etc. Use of biocides (Bacillus thuringiensis) Chemical Control Larvicide: Temephos (Abate)in permanent big breeding containers Adulticide: Pyrethrum spray- in indoor situations as aerosol space spray Malathion fogging or Ultra Low Volume (ULV) spray

Environmental Management & Source Reduction Methods Detection & elimination of mosquito breeding sources Management of roof tops, porticos and sunshades Proper covering of stored water Reliable water supply Observation of weekly dry day

Health Education for Community Participation and Inter- Sectoral Convergence At the household level At the community level At the institutional level

Legislative Measures Model civic byelaws Building Construction Regulation Act Environmental Health Act (HIA) Health Impact Assessments