Dengue is a viral disease that is transmitted by the bite of a female mosquito named Aedes Aegypti, which is already infected by the virus. Aedes aegypti is a daytime feeder and the peak biting periods are early in the morning and in the evening before dusk.
The virus responsible for causing dengue is called dengue virus (DENV). There are four DENV serotypes (DENV-1, -2, -3, and -4). Infection with one serotype of DENV provides immunity to that serotype for life but provides no long-term immunity to other serotypes. Thus, a person can be infected as many as four times, once with each serotype.
Dengue infection usually develops five to six days after being bitten by the mosquito. Dengue causes a wide spectrum of diseases, which can range from subclinical disease (people may not know that they are infected) to severe flu-like symptoms. Though less common, some people develop severe dengue or Dengue Haemorrhagic Fever (DHF), which is the leading cause of serious illness and death.
According to a recent update by the Centre for Disease Control (CDC) each year, up to 400 million people get infected with dengue and approximately 100 million people get sick due to infection, and 40,000 die from severe dengue. The risk of dengue infection exists in 129 countries, however, 70 percent of the actual burden is in Asia. According to National Vector Borne Disease Control Programme, Ministry of Health and Family Welfare, as of September 2021, a total of 60,112 cases of dengue were reported in India.
The country is seeing an exponential rise in dengue cases, in several states including Delhi, Haryana, Kerala, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh, Uttarakhand, and Jammu Kashmir. Dengue cases in Delhi this season have surged to over 5,270, making it the highest recorded in the city in a year since 2015. More recently, as of November 1, according to Union Health Ministry data, a total of 116,991 cases were recorded in India.
Also Read: How mosquitoes transmit disease, explained
Along with the four dengue viruses, Chikungunya and Zika virus are also spread primarily through the bite of an infected Aedes species (Ae. aegypti and Ae. albopictus) mosquito. The prevention of these vector-borne diseases can be done by reducing the size of mosquito population. People must not keep stagnant water at home and in the surroundings nearby as the mosquito can fly up to 400 meters looking for water-filled containers to lay their eggs. They should use mosquito repellents, mosquito nets/screens, wear protective clothing to prevent themselves from being bitten.
A person suspected of having dengue fever or DHF must see a doctor at once. With early detection and proper case management and symptomatic treatment, mortality can be reduced substantially. A definitive diagnosis is made either by detecting the virus/viral genes (antigen or RT-PCR based tests) or specific antibodies (IgG and IgM antibodies) against the dengue virus in the blood samples along with complementary tests like complete blood count with leukocyte and platelet counts. Depending on when a patient reports the illness, the application of different diagnostic is appropriate.
It is advisable that patient samples collected during the first week of illness should be tested by both serological and virological methods (RT-PCR). While diagnosing, it should be kept in mind that some symptoms can be confused with those of other diseases such as malaria, rubella, measles, typhoid fever and influenza. Hence, an RT-PCR-based tropical fever panel, which also includes detection of Chikungunya and Zika virus, could be advisable in an acute phase of infection. Dengue virus and SARS-CoV-2 can cause similar symptoms in the early stages hence COVID-19 should also be ruled out in these cases.
No drug or vaccine is available for the treatment of dengue. Those infected are advised to take rest, stay hydrated and take antipyretics to control their temperature. Children with dengue are at risk for febrile seizures during the febrile phase of illness, which should be monitored.
Patients should avoid taking aspirin and other nonsteroidal, anti-inflammatory medications because they increase the risk of haemorrhage. Patients with severe dengue should be admitted to the hospital immediately for continuous monitoring.
COVID-19 and dengue
COVID-19 pandemic has placed immense pressure on the health care and management systems worldwide. WHO has emphasised the importance of sustaining efforts to prevent, detect and treat vector-borne diseases such as dengue during this crucial period. The combined impact of COVID-19 and dengue epidemics can potentially result in devastating consequences for the populations at risk.
The author Dr Gunisha Pasricha, Principal Scientist, at MedGenome Labs. The views expressed are personal.