Fifteen years after the 2009 influenza pandemic and 5 years after the emergence of SARS-CoV-2, infectious disease researchers are again raising a familiar warning. Novel respiratory viruses of animal origin are circulating quietly, adapting steadily, and largely escaping routine detection.
In a recent review published in the January issue of Emerging Infectious Diseases, a journal of the CDC, researchers highlight 2 emerging pathogens that warrant far greater attention: influenza D virus and canine coronavirus HuPn-2018. According to the authors, both viruses show “considerable potential for causing future human epidemics,” yet diagnostics and surveillance remain limited.
“Two newly recognized emergent respiratory viruses, influenza D and canine coronavirus HuPn-2018, have been shown to have considerable potential for causing future human epidemics, but diagnostics and surveillance for the viruses are lacking,” the authors wrote.
“As an epidemiologist, I find these 2 viruses particularly fascinating—and frustrating—because they represent a shift in where we anticipate ‘the next global pandemic’ to come from,” Brenna Doran, PhD, MA, ACC, CIC, AP-CIP, told ICT. She is a member of the ICT Editorial Advisory Board and the founder and CEO of Innovative Partners Institute. “For decades, the focus has been on wild birds (Bird Flu) and bats (COVID-19). Influenza D and canine coronavirus HuPn-2018 are different because they are emerging from animals we live with every single day: cows and dogs.”
Influenza D Virus and a Widening Host Range
Influenza D virus was first detected in pigs with respiratory illness in 2011, but subsequent research has revealed a far broader host range. The virus has now been identified in cattle, camels, deer, giraffes, kangaroos, llamas, wallabies, wildebeests, and poultry. Cattle appear to be the primary reservoir, and influenza D is now recognized as a contributor to bovine respiratory disease complex, a condition estimated to cost the US cattle industry more than $1 billion annually.
Although no viable influenza D virus has yet been isolated from humans, mounting evidence suggests zoonotic transmission. In a 2016 seroepidemiologic study, these researchers found that more than 97% of cattle workers in Florida had antibodies to influenza D virus, compared with just 18% in nonexposed controls. Their 2023 study of dairy workers in Colorado found molecular evidence of influenza D virus in nasal samples from 67% of workers during a 5-day period.
If you were advising hospital leadership or public health agencies today, what practical investments or policy changes would you recommend to better prepare for emerging respiratory viruses that may already be circulating under the radar?
Shahbaz Salehi, MD, MPH, MSHIA, recipient of the 2024 Infection Control Today Educator of the Year AwardTM and a member of the ICT editorial advisory board, answered:
“I would recommend that public health agencies require hospitals and clinics to participate in a unified, real-time information exchange platform,” Salehi, who is the director of infection prevention and control—employee health at Foothill Regional Medical Center in Tustin, California, answered. “This platform would allow health care facilities to share critical operational data such as respiratory patient census, ICU capacity, staffing constraints, PPE and supply availability, and testing capability.
“While some regions in the US have begun piloting similar systems, participation remains voluntary. Experience has shown that voluntary adoption leads to fragmented data and delayed situational awareness. Without a mandate, many hospitals will not prioritize participation due to competing operational and financial pressures. Making participation a requirement, similar to existing reporting obligations, would enable earlier detection of emerging respiratory threats, improve resource coordination across facilities, and allow public health agencies to respond proactively rather than reactively.”
More recently, researchers in China reported data that raise additional concern. Their work demonstrated airborne transmission between ferrets, replication in primary human airway epithelial cells, and widespread serologic evidence of infection in humans. Based on these findings, the authors concluded that influenza D virus “has acquired the capacity for human-to-human transmission” and that existing strains “already pose a potential panzootic threat.”
Canine Coronavirus HuPn-2018 and Missed Diagnoses
The second virus highlighted in the review, canine coronavirus HuPn-2018, is even more troubling from a diagnostic standpoint. First identified in 2021 after isolation from a child hospitalized with pneumonia in Malaysia, the virus is a recombinant alphacoronavirus with genetic material from canine and feline coronaviruses.
Since that initial discovery, similar viruses have been detected in humans with respiratory illness in Thailand, Vietnam, Haiti, and the US state of Arkansas. In one study in Vietnam, researchers detected the virus in 18 of 200 hospitalized pneumonia patients.
“Recently, we detected CCoV-HuPN-2018 among 18 of 200 pneumonia patients hospitalized in the area of Hanoi, Vietnam, suggesting that this virus may have a wide geographic distribution and variable (and possibly increasing) prevalence,” the authors wrote. “The virus is entirely missed by common clinical diagnostics tests for the detection of respiratory viruses.”
Despite this growing footprint, the virus remains invisible to standard respiratory diagnostic panels. As the authors note, “The virus is entirely missed by common clinical diagnostic tests for the detection of respiratory viruses.”
Although current evidence does not yet prove that canine coronavirus HuPn-2018 is a frequent cause of severe disease worldwide, laboratory studies suggest it may be evolving. The authors caution that earlier strains may not have efficiently infected humans, but increasing detection rates raise concern that adaptation is underway.
“When possible, such surveillance should be strategically focused at the human–animal nexus where we recognize the risk is high,” the authors wrote. “For instance, the risk for novel swine viruses spilling over from swine to infect swine workers is exceedingly high compared with the similar risk for avian influenza viruses spilling over from poultry to infect poultry workers.”
A Familiar Lesson From Recent Pandemics
The authors frame their warning within a broader historical context. “Although science has developed effective countermeasures for most bacterial and vector-borne emerging pathogens, novel respiratory viruses continue to cause large-scale human epidemics,” they wrote, particularly those of zoonotic origin.
Without improved surveillance, targeted diagnostics, and early countermeasure development, influenza D virus and canine coronavirus HuPn-2018 could follow the same trajectory as past pandemic viruses. The researchers argue that proactive investment now may determine whether these pathogens remain obscure curiosities or become the next global respiratory threat.
