A new study from Indian researchers has found evidence to suggest that even first-time, or primary, infections of dengue can be deadly, challenging the prevailing understanding that only second or subsequent (secondary) infections resulted in severe or life-threatening situations.
The new insight was the result of collaborative work by researchers from institutions such as the Delhi-based International Centre for Genetic Engineering and Biotechnology (ICGEB); All India Institute of Medical Sciences (AIIMS), New Delhi; Christian Medical College, Vellore; and Emory University, Atlanta, in the US state of Georgia; among others. Their findings have recently been published in the journal Nature Medicine.
The research involved the study of 619 children admitted to three different hospitals. It was found that primary dengue infections accounted for more than half of the total number of clinical cases (344 of 619), severe cases (112 of 202), and fatalities (5 of 7). The findings could have important implications for dengue vaccine research and its treatment.
“The results of this study mean that primary infections cannot be ignored any longer. It also has global significance as worldwide expansion of the dengue viruses is expected to continue and more children and dengue-naive populations could eventually face the risk of dengue infection, severe disease and fatality,” Dr Anmol Chandele, an Associate Professor at ICGEB, and one of the researchers involved in the study, told The Indian Express.
Dengue, a mosquito-borne viral illness, can result in a spectrum of clinical presentations – from mild fever to severe hemorrhagic fever and potentially fatal dengue shock syndrome.
Dengue infections have greatly increased in India in the past two decades. Data from the Central government’s National Centre for Vector Borne Disease Control indicates that in the last three years, there were over 5.20 lakh dengue cases and 740 deaths. There were 1,93,245 cases and 346 deaths in 2021, 2,33,251 cases and 303 deaths in 2022, and 94,198 cases and 91 deaths in 2023.
Despite its global impact and ongoing efforts to identify a universally approved vaccine and effective therapies, the prevalence of dengue has surged dramatically since the 1970s, now affecting more than 130 countries and causing an estimated 390 million infections and 100 million clinical cases annually.
Dengue infections are caused by four serotypes – four closely related viruses that attack the immune system in different ways – and studies have suggested that people can get lifelong immunity to the serotype that they were infected with. However, there is evidence to show that immunity to one serotype could exponentially increase the likelihood of severe disease if infected later with another serotype.
Most of these studies are from Southeast Asia and South America – regions that have seen dengue infection much before India, which experienced its first outbreak in the 1960s and then saw sporadic cases in the next few decades.
It is only very recently that dengue transmission became consistent, and one recent modelling study suggested that India itself has around 30-40 million infections annually and that India is the epicentre of dengue infections. What was not known is the proportion of primary-versus-secondary dengue infections and how this correlates with disease severity.
In the latest study, researchers examined children with confirmed fever-associated dengue from three hospitals in different regions of India. Three tertiary care centres – St John’s Research Institute (SJRI), All India Institute of Medical Sciences (AIIMS) and Christian Medical College – participated in the study where 619 children with confirmed dengue were studied between 2012 and 2018. “Our findings question the currently widely-held belief that severe dengue is associated predominantly with secondary infections and emphasises the importance of developing vaccines or treatments to protect dengue-naive populations,” Dr Chandele said.
Rohit Malhotra is a medical expert and health journalist who offers evidence-based advice on fitness, nutrition, and mental well-being. His articles aim to help readers lead healthier lives.
