Primary dengue virus infections constitute a substantial fraction of severe disease cases and fatalities, states a new published study questioning the currently widely held belief that severe dengue disease is mainly due to secondary dengue infections.
Dengue is a viral infection caused by the dengue virus (DENV), transmitted to humans through the bite of infected mosquitoes.
Patients who are infected by any DENV for the first time are known as cases of primary dengue infection. Patients who were previously infected by another DENV and then present with infection from a new serotype are known as cases of secondary dengue infection.
The study published in Nature Medicine recently did an analysis of severe dengue cases in a large group of children in India and found that more than half could be attributed to primary rather than secondary infection.
Anmol Chandele, group leader of the International Centre for Genetic Engineering and Biotechnology (ICGEB)-Emory Vaccine Program at ICGEB New Delhi, India, in collaboration with Emory School of Medicine, Atlanta, USA, the All India Institute Of Medical Sciences (Delhi), and St. John’s National Academy of Health Sciences, (Bengaluru) authored the paper on “Severe disease during both primary and secondary virus infections in paediatric populations.”
‘Important implications’
“This finding has very important implications for public health across the world and also in developing and implementing effective and safe vaccine strategies for controlling dengue. These findings are highly relevant not only in the Indian context where burden of dengue disease is considerable but also on a global scale since dengue viruses continue to spread worldwide,’’ said Dr. Chandele.
“Our study shows that primary infections constitute a substantial fraction of severe disease cases and fatalities,’’ she adds.
‘Case increase in India’
The paper notes that over the past two decades, dengue infections have greatly increased in India and that the country now has one of the largest number of dengue cases globally.
“With four serotypes of the dengue virus, typically, dengue patients fall into two categories — one, those experiencing the infection for the first time, known as primary infections and those, who get re-infected after a previous exposure, known as secondary infections,’’ the paper explains.
Traditionally, the prevailing belief has been that only secondary infections pose significant risks, leading much of the research into vaccine development and treatment to focus on this group. But now this widely held perception seems to lose its ground.
“This finding suggests a need to re-evaluate our understanding of dengue and the strategies employed to combat it,’’ notes the lead author.
According to data, India contributes to a third of the total global dengue burden and has been identified as one of the four main infections threatening global health by the World Health Organization (WHO).
High burden areas
In India, West Bengal, Uttar Pradesh, Punjab, Haryana, Delhi, Gujarat, Kerala, Karnataka and Tamil Nadu being identified as the high burden areas.
A paper published in the medical journal Lancet titled “The resurgence of dengue epidemic and climate change in India” notes that dengue disease has steadily increased in the past half century due to global trade and travel, urbanisation, population growth, and climate variability and change etc.
The incidence of dengue has grown dramatically around the world in recent decades, with cases reported to WHO increased from 5,05,430 cases in 2000 to 5.2 million in 2019. A vast majority of cases are asymptomatic or mild and self-managed, and hence the actual numbers of dengue cases are under-reported. Many cases are also misdiagnosed as other febrile illnesses,” adds the WHO. There is no specific treatment for dengue/severe dengue, and early detection and access to proper medical care greatly lower fatality rates of severe dengue.
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