Beyond the Usual Suspects: Emerging Animal Viruses That Could Shape the Next Human Outbreak

Emerging research warns that influenza D virus and canine coronavirus—two animal-origin viruses—may pose underestimated risks to human health. Limited surveillance, evolving transmissibility, and low population immunity highlight the need for a One Health approach to prevent future outbreaks.

Animal-origin viruses continue to remind the global health community that the next outbreak may not come from an unfamiliar place—but from pathogens we are already overlooking. A new review published in Emerging Infectious Diseases, the journal of the Centers for Disease Control and Prevention, highlights two such concerns: influenza D virus and canine coronavirus.

According to the authors, both viruses have demonstrated the ability to infect humans, yet surveillance, diagnostics, and preparedness efforts remain limited. If either virus evolves efficient human-to-human transmission, the lack of population immunity could allow widespread outbreaks to occur.

Influenza D: Widespread Exposure, Limited Awareness

First identified in 2011, influenza D virus has been detected in a broad range of animal species, including cattle, pigs, poultry, deer, and other wildlife. It is considered a contributor to bovine respiratory disease, which costs the U.S. cattle industry an estimated $1 billion annually.

Human exposure appears to be far more common than previously assumed. Studies of cattle workers in Colorado and Florida found that up to 97% carried antibodies to influenza D virus, indicating prior infection. To date, these infections have been subclinical, but researchers caution that the virus has characteristics consistent with rapid evolution. Notably, a strain recently identified in China has demonstrated the ability to transmit between humans.

While no severe human illness has yet been linked to influenza D, experts warn that the virus’s expanding host range and genetic adaptability warrant closer monitoring.

Canine Coronavirus: A Quiet Zoonotic Signal

Canine coronavirus (CCoV), best known for causing gastrointestinal disease in dogs, is distinct from SARS-CoV-2 but has increasingly been associated with human respiratory illness. Rare but documented human infections have been linked to pneumonia and hospitalization, particularly in Southeast Asia.

In 2017, researchers at the University of Florida isolated a novel canine coronavirus strain from a medical worker who developed mild illness after traveling to Haiti. That strain, later named HuCCoV_Z19Haiti, closely resembled another strain identified in 2021—CCoV-HuPn-2018—isolated from a hospitalized child in Malaysia.

Since then, related canine coronavirus strains have been detected in people with respiratory illness in Thailand, Vietnam, and even the United States, including Arkansas. These findings suggest the virus is already circulating across continents, largely undetected due to the absence of routine diagnostic testing.

A Familiar Lesson, Revisited

The emergence of influenza D virus and human-infecting canine coronaviruses reinforces a lesson underscored by recent pandemics: early warning signs are often present long before widespread transmission occurs. Without proactive surveillance, improved diagnostics, and targeted research into treatments and vaccines, these viruses could gain a foothold in human populations.

The authors emphasize that current knowledge of these pathogens is based on a relatively small number of studies, yet even limited data indicate meaningful public health risk. A coordinated One Health approach—integrating veterinary, medical, and environmental surveillance—may be essential to identifying and mitigating these threats before they escalate.

As history has shown, waiting until human-to-human transmission is established may be waiting too long.

Source
Gray, G. C., et al. (2026). Emerging Respiratory Virus Threats from Influenza D and Canine Coronavirus HuPn-2018.Emerging Infectious Diseases, 32(1).