In recent times, Delhi has seen a rise in the reports of dengue cases. Despite this, current case counts remain the lowest they have been in last four years. The city experienced its worst dengue outbreak back in 2015 with more than 15,000 reported cases and 60 unfortunate fatalities.
Understanding Dengue
Dengue is a viral disease spread primarily by the Aedes aegypti mosquito species and, to a lesser extent, by the Aedes albopictus species. These same mosquitoes are also responsible for spreading diseases like chikungunya, yellow fever, and the Zika infection. The virus causing dengue, known as the dengue virus, is typically found throughout tropical regions. The risk potential of dengue in these regions can vary based on factors such as rainfall, temperature, and rapid urbanisation.
The Inception and Impact of Severe Dengue
Dengue was first recognised as a severe disease during the 1950s following epidemics in the Philippines and Thailand. The severe form of dengue, also known as Dengue Haemorrhagic Fever, is now dominant in many Asian and Latin American countries. It often causes significant hospitalizations and deaths among both children and adults.
The Dengue Virus Serotypes
The dengue virus consists of four closely related, but distinct serotypes: DEN-1, DEN-2, DEN-3, and DEN-4. Each provides lifelong immunity against itself when an individual recovers from the infection. However, the immunity offered against the other serotypes post-recovery is only temporary and partial. Therefore, subsequent infections by different serotypes heighten the risk of severe dengue.
| Type | Characteristics |
|---|---|
| DEN-1 | Can cause dengue fever and severe dengue |
| DEN-2 | Associated with Dengue Haemorrhagic Fever, dengue shock syndrome, and severe dengue |
| DEN-3 | Primarily causes dengue fever and occasionally severe dengue |
| DEN-4 | Not typically associated with severe disease |
Dengue in Delhi
The prevalence of the DEN-3 serotype in Delhi over the last three years partly explains the recent decline in dengue cases in the city. If a serotype remains in circulation for an extended period, it leads to the development of immunity among a large portion of the population. However, the re-emergence of a serotype after a period of absence can trigger a sudden surge in dengue cases. Constant monitoring of the prevalent strains throughout the year to identify shifting serotypes is critical.
Need for Awareness and Monitoring
In any case of migration from a state carrying a different serotype strain, there could be a potential spread of this strain amongst the local population, complicating the situation. As such, the role of public awareness about dengue and its prevention methods becomes vital. The collective effort of an informed public can go a long way in controlling the spread of this disease.