DENGUE

General Studies Paper 2

Context: Serum Institute of India and Panacea Biotec apply for Expression of Interest for clinical trials for indigenous manufacturers of Dengue vaccine.

Dengue Virus (DENV)

• Dengue is a viral infection caused by the dengue virus (DENV), transmitted to humans through the bite of infected mosquitoes.
• DENVis a pathogenic arthropod-borne flavivirus (arbovirus), it is a single-stranded and positive-sense RNA molecule belonging to the family

Geographical Distribution

• Dengue is found intropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
• Presently, DENV is prevalent throughout the different countries (at least 100 countries) including in Asia, the Pacific, the Americas, Africa, and the Caribbean. 

Transmission

• Transmission through the mosquito bite: The virus is transmitted to humans through the bites of infected female mosquitoes, primarily theAedes aegypti mosquito. Other species within the Aedes genus can also act as vectors, but their contribution is secondary to Aedes aegypti.
• Human-to-mosquito transmission: Mosquitoes can become infected by people who are viremic with DENV. This can be someone who has a symptomatic dengue infection, also people who show no signs of illness as well (they are asymptomatic).
  • 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.
• Maternal transmission: There is evidence of the possibility of maternal transmission (from a pregnant mother to her baby).
• Other transmission modes: Rare cases of transmission via blood products, organ donation and transfusions have been recorded. Similarly, transovarial transmission of the virus within mosquitoes have also been recorded.

Symptoms

• high fever (40°C/104°F)
• severe headache
• pain behind the eyes
• muscle and joint pains
• Nausea
• Vomiting
• swollen glands
• Individuals who are infected for the second time are at greater risk of severe dengue. Severe dengue symptoms often come after the fever has gone away:
  • severe abdominal pain
  • persistent vomiting
  • rapid breathing
  • bleeding gums or nose
  • Fatigue
  • Restlessness
  • blood in vomit or stool
  • being very thirsty
  • pale and cold skin
  • feeling weak.

Prevention

• The mosquitoes that spread dengue are active during the day. The risk of getting dengue can be reduced by:
  • clothes that cover as much of your body as possible.
  • mosquito nets if sleeping during the day, ideally nets sprayed with insect repellent window screens.
  • mosquito repellents (containing DEET, Picaridin or IR3535).
  • Avoid water collection around the house to prevent breeding of mosquitoes. If needed, one must cover water with a lid to refrain breeding.
  • coils and vaporizers.

Treatment

• Rest
• drink plenty of liquids
• use acetaminophen (paracetamol) for pain
• avoid non-steroidal anti-inflammatory drugs, like ibuprofen and aspirin
• watch for severe symptoms.
• So far one vaccine (Dengvaxia) has been approved and licensed in some countries. However, only persons with evidence of past dengue infection can be protected by this vaccine. Several additional dengue vaccine candidates are under evaluation.

Vaccines Proposed

• Two potential vaccines that Serum Institute of India initiated is to conduct Phase-III randomised, double-blind, placebo-controlled trials in 10,335 healthy adults (aged 18-80 years) in 20 sites (ICMR-funded).
• The Phase-III protocol has been approved by the Drugs Controller General of India (January 2023) and the company is trying to upscale vaccine production with the trials expected to start in August-September this year.
• ICMR has noted that the desirable characteristics of a dengue vaccine includes acceptable short- and long-term safety profile(no antibody dependent enhancement), inducing protection against all four serotypes of dengue, reducing risk of severe diseases and deaths, inducing a sustained immune response and effectiveness irrespective of the earlier sero-status and age of the individual.

Why India Sees Massive Dengue Outbreaks Every Year

• Poor sewer systems lead to pooling of water in many of the cities in India which leads to breeding of mosquitoes.
• Many people store water in their habitat because of shortage of water in many parts of India. This makes the place perfect for breeding mosquitoes.
• There are no adequate efforts from the government to develop a vaccine against Dengue because of other prevalent health conditions.
• Lack of awareness in the community to prevent mosquito bites and to avoid breeding places for mosquitoes.