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.
Continued….• 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
Continued….• 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
Continued….• Eastern Mediterranean– 4 endemic countries• Recent major epidemics in Diboti, Saudi Arabia and Pakistan• Multiple serotypes are circulating• Sporadic cases of DHF documented
Continued….• 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
Continued….• 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
Continued….• 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.
Continued….• 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.
Continued….• 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.
Continued….• Medical measures:• Passive surveillance• Active surveillance• Early diagnosis and treatment of cases.• Integrated vector control and inter-sectoral cooperation