A sudden rise in dengue cases has been reported from multiple states. While Uttar Pradesh has been the hardest hit, with scores of deaths, Maharashtra, Madhya Pradesh, Haryana, too, are among the states that have tracked a jump in the number of dengue cases. Amid efforts to combat the Covid-19 pandemic, health authorities and medical staff are now scrambling to respond to the increase in dengue cases. Last week, officials had pointed to a particular strain of dengue — DENV2 or D2 — as being behind the deaths in UP. Here’s all you need to know about it.
What Is D2 Dengue?
Dengue is a mosquito-borne fever that is common throughout India. It has, in fact, been described as the “most important mosquito spread viral disease and a major international public health concern", in guidelines for prevention and control of the disease released jointly by the National Centre for Disease Control (NCDC) and the World Health Organisation (WHO). The disease is found mostly in tropical and sub-tropical climates and is prevalent mainly in urban and semi-urban areas.
While it is the dengue virus, named as DENV, that causes the disease, there are actually four, closely-related, forms that it can take. These four serotypes — DENV-1, DENV-2, DENV-3, DENV-4 — mean that dengue can potentially strike an individual four times. Which is to say, while infection with one strain is generally seen as conferring immunity for life against that strain, it is still possible to get infected with the remaining three strains.
“While many DENV infections produce only mild illness, DENV can cause an acute flu-like illness. Occasionally this develops into a potentially lethal complication, called severe dengue," the WHO says.
Talking about the outbreak in western Uttar Pradesh, Balram Bhargava, the Director-General of Indian Council of Mecical Research (ICMR) said that the DENV-2 or D2 variant of dengue was “behind the surge in fever cases and deaths in western UP districts of Firozabad, Agra, Mathura and Aligarh", adding that this strain is as virulent as it is deadly.
Earlier, in July this year, amid the detection of a large number of cases of dengue in Odisha, a report had cited a researcher at ICMR’s Regional Medical Research Centre at Bhubaneswar as saying that “subtype-2 is most pathogenic". “Its second attack is more dangerous as the macrophages facilitate viral entry. This subtype also leads to dengue shock syndrome,” the researcher had said.
What Makes D2 Dengue Lethal?
The WHO says that “dengue causes a wide spectrum of disease", ranging from types where people may not even know that they are infected to severe flu-like symptoms. It adds that some people can develop severe dengue, although such instances are “less common". Severe dengue — which was first recognised in the 1950s during dengue epidemics in the Philippines and Thailand — “has a higher risk of death when not managed appropriately", it says.
Reports say that severe dengue is the term used now for what was earlier known as ‘dengue haemorrhagic fever’ and ‘dengue shock syndrome’ following a reclassification by WHO in 2009.
Severe dengue cases are now seen in almost all Asian and Latin American countries and “has become a leading cause of hospitalisation and death among children and adults in these regions".
Talking about the conditions in which individuals can develop severe dengue, NCDC says that “when a person has had classic dengue (that is, infection by one serotype), a second infection later by another serotype increases the likelihood of suffering from dengue haemorrhagic fever (DHF)".
WHO adds that since after infection with one strain of dengue, immunity (cross-immunity) to the other serotypes is “only partial, and temporary", “subsequent infections (secondary infection) by other serotypes increase the risk of developing severe dengue".
What Are The Symptoms Of D2 Dengue?
WHO says that dengue produces flu-like symptoms and lasts for 2-7 days while the incubation period for the disease is usually 4-10 days after the bite of an infected mosquito. The symptoms of this “classic dengue fever", the US Centres for Disease Control and Prevention (CDC) says are high fever accompanied by “at least two" complaints like headache, pain behind eyes, nausea, vomiting, swollen glands joint, bone or muscle pains, rash.
The transition to severe dengue is the tricky part, because for a period, it appears that the patient is actually recovering.
“When developing into severe dengue, the critical phase takes place around 3-7 days after the first sign of illness. Temperature will decrease; this does NOT mean the person is necessarily recovering," WHO says. It urges “special attention" to warning signs that could lead to severe dengue like severe abdominal pain, persistent vomiting, bleeding gums, vomiting of blood, rapid breathing, fatigue/restlessness. Once severe dengue is suspected, the patient “should be rushed to the emergency room or to the closest health care provider" since it can send a a patient into shock through plasma leakage, severe bleeding and severe organ impairment.
What Are The Treatments?
There are no vaccines or specific treatments for dengue and patients have to depend on the management of symptoms.
“Patients should seek medical advice, rest and drink plenty of fluids. Paracetamol can be taken to bring down fever and reduce joint pains. However, aspirin or ibuprofen should not be taken since they can increase the risk of bleeding," WHO advises.
It points out that proper medical care and early detection can keep case-fatality rates below 1 per cent, but notes that the “the overall experience remains very discomforting and unpleasant".
(An earlier version of this article was published on September 10, 2021)
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