Dengue is an zoonotic disease caused by dengue virus and transmitted by anopheles mosquitoes. It is an endemic disease affecting almost all parts of our country, especially Delhi and NCR, Uttar Pradesh, Maharastra, Orissa, Kolkata and Punjab. This disease is responsible for a number of mortalities every year and has plagued the medical fraternity for a number of years.
How does the dengue mosquito cause the deadly disease?
Dengue is an arbovirus, family flaviviradeae and has 4 genetically distinguishable serotypes (DENV 1, DENV 2, DENV 3, and DENV4). Following blood meal from DENV affected patients the virus replicates in the midgut of aedes mosquito. In 8-12 days it spreads systemically and reaches salivary glands making it infective for human host( extrinsic incubation period).The intrinsic incubation period ( period for virus replication within the host), varies from 3- 14 days. The course of dengue infection is self limiting in majority of cases. Only in very few cases it progresses to severe dengue infection.
Following bite of infected mosquito, virus replicates in specific cells, followed by transient viremia leading to spread all over the body. After replication in different organs the virus is released in to the blood causing frank viremia within two to six days of subcutaneous injection. Viremia is detectable in humans 6-18 hours before the onset of symptoms and last for 3-5 days. Innate and adaptive immune systems are activated in response to DENV infection.
Macrophages are the first line defense against any viral infection. In dengue viral infection it plays multiple paradoxical roles. Sometimes it help in eradicating the virus and it may help in viral replication.
So since single mosquito can bite many persons at a time so it is communicable in a sense, but it cannot be transferred from a human to another human directly. It can also be transferred by blood transfusion, although the reports are only very few.
For dengue we can say – Prevention is better than to be infected and get treatment.