Epidemiology, Prevention and Control of Dengue Fever

Dr. Gopalrao Jogdand, Ph.D. (U.S.A.)Professor & Head,

Car Medical College, Karim Nagar

Historical Background

• Dengue epidemics are known to have occurred over the last three centuries in tropical, sub tropical and temperate zones

• The first epidemic of dengue was recorded in 1635 in the French West Indies.

• Rush described about Break bone fever occurred in Philadelphia in 1780.

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• The first recorded outbreak of DHF occurred in Australia in 1897.

• Similar disease was found in Greece in 1928 and in Taiwan in 1931.

• First confirmed epidemic of DHF was recorded in Philippines in 1953-54

• Now prevalent in India, Indonesia, Myanmar, Sri lanka, New Caledonia, countries of western Pacific region.

Magnitude of the Problem

• There are 2.5 to 3 billion people are at the risk and living in epidemic prone areas globally

• South East Asia 100 million cases annually and 500,000 cases of DHF of which almost 90% are children

• The mortality rate is 5% causing 25,000 deaths annually

• Epidemics are cyclical

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• Africa----- 20 Endemic countries• Epidemics have been caused by all four

serotypes in the past 18 years• Recent major epidemics have been reported

in Comores and Eritrea• DHF not reported

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• Eastern Mediterranean– 4 endemic countries• Recent major epidemics in Diboti, Saudi

Arabia and Pakistan• Multiple serotypes are circulating• Sporadic cases of DHF documented

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• Western Pacific– 29 countries endemic• Recent major epidemics are reported I

Singapore, Cambodia, Vietnam, Philippines, Tahiti, Fiji and Palau

• All four serotypes circulating• DHF is a major public health problem and

disease is endemic in many countries

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• Americas– 42 Endemic Countries• Recent major epidemics in Central America,

Colombia, Peru, Venezuela, Brazil, Mexico, Cuba, Puerto Rico, Barbados and Trinidad

• All 4 serotypes are circulating• DHF is a newly emerging disease and now

occurs in 24 Countries

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• South East Asia– 7 Endemic countries• Recent major epidemics are reported from

India, Sri Lanka, Myanmar and Indonesia• All 4 serotypes are circulating• DHF is a major cause for hospitalization and

deaths of children

The Agent

• Dengue is caused by a virus member of the genus Flavivirus and family Flaviviridae.

• Virus is 50nm. in size and contains a single strand RNA.

• There are 4 serotypes of this virus DEN1, DEN2, DEN3 and DEN4

• There is a short lived cross immunity between these species

The Vector

• Globally Aedis aegypti is a important vector but has geographical limitation

• Other species are Aedis albopictus, A. Stegomyia, A. ploynesiensis, A. scutellaris and A. finalaya and in India A. tigris

• The most potent vector having epidemic potential is A. aegypti

Habits and habitat of the vector

• Vector: Aedis tigris mosquito in India, Aedis aegypti, stegomyia and albopictus in other countries.

• Habits of the vector: Clear water breeder, day time biter and domestic breeder

• Responsible for the transmission of Dengue fever, Dengue hemorrhagic fever and Dengue shock syndrome.

The Host

• Dengue virus infects humans and other lower primates

• Humans are main urban reservoirs of the disease

• Studies conducted in Africa and Malaysia show that monkeys are infected and can be reservoirs of the disease

Transmission Cycle

• Extrinsic incubation period: 8 to 10 days.• Intrinsic incubation period: 3 to 14 days an

average of 4 to 7 days.• Cyclic nature of the disease: In endemic

countries the cycle can be repeated at yearly interval.

• India is a endemic country for dengue fever.

Characteristics of the disease

• It is caused by a virus called flavi virus.• Virus gets access to human body by the bite of

a infected mosquito.• Causes three types of clinical manifestations:• Dengue Fever: High grade fever and joint pains.• DHF: dengue hemorrhagic fever causes

cutaneous hemorrhages and platelet depletion.

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• Dengue shock syndrome: Fever, cutaneous rash, GIT bleeding, severe bleeding, shock and multiple organ failure.

• Risk factors for dengue fever:• Immune status of the patient.• Infecting virus strain and its virulence.• Age of the patient.

Factors responsible for resurgence of Dengue

• Unprecedented population growth• Unplanned and uncontrolled urbanization• Increased distribution and vector density• Inadequate waste management and water

supply• Development of hyperendemicity• Inadequate health infrastructure

DHF as a serious Public Health Problem

• Seven out of ten countries have serious DHF problem

• DHF is a major cause for hospitalization and death of children in these countries

• Incidence of DHF has increased five times in the last 30 years beginning from 1980

• The geographic distribution has increased within countries and in other countries of the region.

Prevention & Control

• Elimination of breeding places of mosquito.• Avoidance of man------- mosquito----- virus

contact.• Drinking water storage containers are to be

drained at the interval of 3-4 days.• Proper cleaning of overhead water storage

tanks, never leave the tanks uncovered.

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• Coolers and desert coolers should be dried and then kept aside.

• Used tyres, bottles and containers should be disposed of properly.

• Personal protection:• Use of mosquito nets, repellant creams,

mosquito coils, mats and aerosols.

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• Medical measures:• Passive surveillance• Active surveillance• Early diagnosis and treatment of cases.• Integrated vector control and inter-sectoral

cooperation

Thank You