Mosquitoes Are The Biggest Mass Killer on Earth
Dengue fever is an infection of tropical and subtropical regions. Dengue virus belongs to family Flaviviridae, having four serotypes that spread by the bite of infected Aedes mosquitoes.
Approximately 2.5 billion people live in dengue-risk regions with about 100 million new cases each year worldwide. The first epidemic of clinical dengue-like illness was recorded in Madras (now
Chennai) in 1780 and the first virologically proved epidemic of DF in India occurred in Calcutta and Eastern Coast of India in 1963-1964. Infection caused by a virus and spread by an insect vector – the mosquito.
Dengue is a Flavi viruses, RNA virus belongs to Arbovirus group, it has four serotypes – Den 1- 4
Cycle involves humans and Aedes mosquitoes. Infection with one virus gives immunity to that serotype only.hence a person can have more than one attack in his lifetime.
Commonly Aedes egyptii less commonly, A albopictus are responsible transmission of dengue
it is a domestic day biting mosquito, prefers to feed on humans. Breeds in stored water like abandoned vehicle tyres, flower pots ,empty plastic cans, air cooler tanks and overhead water tanks. It has short flight range May bite several people in same household.
The reasons for dengue epidemic are uncontrolled urbanization and population growth, poor sense of hygiene among people, substandard housing, inadequate water, sewer and waste management,
Deterioration of public health infrastructure faster travel Ineffective mosquito control in endemic regions Hyperendemicity that is intense transmission among house holds happens because of prevalence of multiple serotypes.
Dengue has Incubation period of2-7 days it starts with sudden fever 40-41 C, nonspecific constitutional symptoms like severe muscle aches and retro-orbital pain. Hepatomegaly ie. Enlarged liver, skin rash and facial flush may be seen. Fever subsides in 2-7 days, and can be may be biphasic.
Diseases like upper respiratory Infections malaria, viral hepatitis, measles, rubella (German measles)
Meningitis ,encephalitis, pyelonephritis and septicemia may be confused with dengue fever.
WHO has classified dengue fever as acute febrile illness with 2 or >more of the following:
Dengue hemorrhagic fever is defined as defervescence of fever and swelling with all of the following must be present:
+ve tourniquet test
Petichiae, ecchymosis or purpura
Bleeding from other sites
Thrombocytopenia (<=100,000/cu mm)
Evidence of plasma leak
Rise in hematocrit > 20% above average
Dengue shock syndrome
In dengue shock syndrome all of the above +will be present alongwith evidence of circulatory failure like Rapid, weak pulse, Narrow pulse pressure < =20 mm hg, Cold clammy skin, Restlessness, Often present with abdominal pain; mistaken for acute abdominal emergency.
Lab Diagnosis of Dengue infection:
- Dengue HI test in paired sera showing 4 fold rise
- IgM type antibodies in late acute/convalescent sera in primary infection
- IgG type antibodies in high titre in secondary infection
- Viral isolation: sensitivity < 50%
- RT- PCR: sensitivity > 90%
- Treatment is supportive.
- No specific treatment of dengue fever is available.antiviral agents for dengue are not employed.
- Analgesics and antipyretics like paracetamol are administered for control of fever
- one must avoid agents which may impair platelet function eg aspirin
- Hospitalisation is required if patient has dengue shock syndrome.
- Closely monitoring for shock and repeated hematocrit measurements may be needed.
- appropriate fluid and electrolyte administration is done to correct dehydration
- If hematocrit is rising by >20%,
- intravenous fluids may be provided
- Antibiotics have no role
- Corticosteroids are not indicated