A growing body of research is turning global scientific attention toward Influenza D virus (IDV), a relatively lesser-known member of the influenza family with zoonotic potential. A study published by the National Library of Medicine, US, highlights early insights into its interaction with humans, revealing both low general prevalence and significant exposure among high-risk groups.
In its paper titled ‘Influenza D,’ the health body revealed, “Serological evidence of previous exposure to IDV infection in humans has been collected from three independent studies. The first study showed that IDV seroprevalence rate in a cohort aged 60 years and older living in Canada and the eastern US (Connecticut) was about 1.3% (4/312) [4]. The observation of low prevalence of IDV in the general population seems to be in agreement with an etiological investigation in Scotland showing no evidence of IDV infection in archived respiratory samples from hospital-visiting patients [31]. The second study focused on an occupational exposure cohort (cattle-exposed farmers) living in Florida and documented a 97% seroprevalence (34/35), which mirrored the seroprevalence in the cattle population [32]. This study also revealed an 18% seroprevalence (2/11) in non-cattle exposed persons. The third study represents a comprehensively longitudinal study of more than 1,000 human serum samples collected in Italy from 2005 to 2017 for examination of the prevalence of antibodies against influenza D virus [33]. The results of this study showed that the prevalence of IDV antibodies increased in the human population in Italy from 2005 to 2017 with up to 33.9–41.0% of surveyed subjects tested positive in some years. “
DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.
While these findings suggest exposure, they do not yet indicate a significant disease burden in humans. Still, experts caution against complacency. Here’s why:
‘A virus to watch, not fear’
“Influenza D is primarily a virus of cattle, with occasional spillover into humans, particularly those in close contact with livestock,” explains Dr Neetu Jain, Senior Consultant, Pulmonology, Critical Care and Sleep Medicine, PSRI Hospital. “At present, it has not demonstrated sustained human-to-human transmission or caused significant illness in people.”
Dr Jain notes that zoonotic viruses become serious threats only when they adapt effectively to human biology. “For a virus to become a public health concern, it must bind efficiently to human receptors, replicate well, and evade immune responses. Influenza D shows only partial compatibility with human airway cells at this stage.”
Why lab findings don’t translate into outbreaks
Laboratory studies have shown that Influenza D can replicate in human respiratory cells, raising questions about its outbreak potential. “Replication in airway tissue is just one part of the equation,” says Dr Jain. “The virus still lacks efficient receptor binding and the ability to overcome innate immune defenses in humans. This limits viral load and reduces its capacity for transmission.”
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She adds that epidemiological data so far do not support human-to-human spread. “Despite some biological competence, Influenza D has not achieved the evolutionary adaptations required for outbreak-level transmission.”
What would it take for Influenza D to spread among humans?
“For Influenza D to achieve sustained transmission, it would likely need mutations that enhance binding to human-type receptors in the upper respiratory tract,” explains Dr Jain. “It would also require improved replication efficiency at human body temperature and mechanisms to evade immune responses, such as interferon activity.”
She points out that structural changes improving airborne stability or increasing viral shedding could further aid transmission. “These changes typically occur gradually through mutation or reassortment, especially in viruses with segmented genomes like influenza.”
All about Influenza D (Photo: Magnific)
Are farm workers at higher risk?
Study suggests that people working closely with livestock are more frequently exposed to the virus. “Serology studies indicate that farm workers and veterinarians often have antibodies against Influenza D, meaning they’ve been exposed,” says Dr Jain. “However, most of these cases are asymptomatic or very mild.”
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This makes such populations crucial for early detection. “They act as sentinel groups. The human-animal interface is where viral adaptation is most likely to begin due to repeated exposure.”
Why surveillance matters now
Although Influenza D is not an immediate threat, experts stress the importance of proactive monitoring.
“Surveillance should be strategic, not reactive,” Dr Jain emphasises. “Routine testing in livestock, genomic sequencing, and monitoring occupational exposure can help detect early changes in the virus.”
She concludes with a note of caution: “Viruses evolve under ecological pressures. While Influenza D is not a current pandemic risk, continuous surveillance ensures that we are not caught off guard if that risk changes.”
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DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.
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