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  • Malkiat Singh Duhra

Dengue Viral Fever

Updated: Jan 23, 2022




Dengue is a mosquito-borne viral disease that has spread in tropical and sub-tropical climates worldwide. Dengue virus is transmitted by female of mosquitoes mainly of the species Aedes aegypti and , to a lesser extent Aedes albopictus . These mosquitoes are also vectors of Chikungunya, Yellow fever, and Zika viruses. It is influenced by rainfall, temperature, relatively humidity, and unplanned rapid urbanization.


Dengue fever can range from sub clinical disease to severe flu-like symptoms in those infected. Severe dengue has a high risk of death when not managed properly. Dengue is caused by a virus ( DENV-1, DENV-2, DENV-3, DENV-4 ). Recovery from infection is believed to provide lifelong immunity against that serotype. Before 1970, only 9 countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries.


Transmission

The virus is transmitted to humans through the bites of infected female of mosquitoes. After feeding of an DENV infected person, the virus replicate in the mosquito midgut. The extrinsic incubation period ( EIP ) is above 8-10 days at

25-28C temperature. Mosquitoes can become infected from people who are infected with DENV. Human to mosquito transmission can occur up to 2 days before someone shows symptoms of the illness, and up to 2 days after the fever has resolved. There is a evidence however, of the possibility of maternal transmission from a pregnant mother to her baby.


Signs and symptoms

Dengue: fever 40C/104F accompanied by two of the following symptoms like; severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen glands and rash.

Severe Dengue: patient enters the critical phase about 3-7 days after illness onset with fever 38C/100F. Severe dengue is a potentially fatal complication, due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding or organ impairment. Other symptoms are like; severe abdominal pain, persisting vomiting, rapid breathing, bleeding gums, fatigue, restlessness, and blood in vomit. It need proper medical care to avoid complications and risk of death. It is important to go for test available ( virological or serological methods ) as advised by your doctor.


Treatment

There is no specific treatment for dengue virus fever. Fever reducer and pain killers like; Acetaminophen or Paracetamol can be taken to control the symptoms of muscle aches and pains, and fever. For severe dengue, consult your doctor immediately and take treatment under the supervision of your medical doctor.

Note: control mosquitoes on large scale in your localities, take care of mosquito breeding places, adopt personal protection from mosquito bites, monitor prevalence of dengue virus in mosquitoes, surveillance of mosquitoes and their chemical control timely, and keep dengue virus patients in isolation to check further spread.


Ecology and biology of mosquito

Mosquito Aedes aegypti is considered the primary vector of dengue virus. It lives in urban habitats and breeds mostly in man- made containers. It is a day time feeder; its peack biting periods are early in the morning and in the evening before sunset. Female frequently feed multiple times between each egg-laying period. Once a female has laid he eggs, these eggs can remain viable for several months, and will hatch when they in contact with water.


Adult female mosquito lay eggs on the inner walls of containers with water above the waterline. Eggs stick to the container walls like glue. They can survive drying out for up to 8 months. The eggs can even survive in winter. Mosquitoes only need a small amount of water to lay eggs. Bowls, cups, fountains, tires, barrels, and any other containers storing water make a breeding place for mosquitoes. Eggs hatch when water from rain or sprinkler cover the eggs. After egg hatching the larva live for 5 days in water. Larvae can be seen in water moving quickly as these are very active. Larvae pupate and pupae live in water for 2-3 days, then adult emerge from the pupa and fly away. Adult female mosquitoes bite people and animals. Female mosquitoes need blood to produce eggs. After feeding female look for water sources to lay eggs. Adult don’t fly long distances and fly within 1-2 kilometres in its lifetime. In favourable conditions mosquito complete it’s life cycle ( egg to adult) in 7-10 days.




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