Leading scientists have issued an urgent warning that two little-known animal viruses, influenza D and canine coronavirus, could easily spark the next pandemic if they jump to humans. This alert comes amidst a severe winter illness season in the US, where influenza has already affected approximately 20 million people and caused over 11,000 deaths since October, according to federal data. However, researchers emphasize that the greater long-term danger may stem from these less-monitored animal-borne pathogens.

A new review highlights that influenza D (IDV), primarily infecting cattle, and canine coronavirus (CCoV), a highly contagious virus in dogs, possess the potential to mutate and spread among humans. While neither virus is currently known to circulate widely in people, their ease of transmission in animal populations and inadequate monitoring mean that mutations enabling human-to-human spread could go undetected. Dr. John Lednicky, a research professor at the University of Florida and co-author of the CDC-backed paper published in January, stated, "Our review of the literature indicates these two viruses pose respiratory disease threats to humans, yet little has been done to respond to or prevent infection. If these viruses evolve the capacity to easily transmit person to person, they may be able to cause epidemics or pandemics since most people won't have immunity to them."

Influenza D virus (IDV) was first identified in US pigs in 2011 and has since been found in a diverse range of animals including cattle, chickens, deer, giraffes, and even kangaroos. Like other influenza viruses, IDV mutates readily, with researchers noting its strains can "reassort and recombine," indicating rapid evolution. It shares a close genetic relationship with influenza C, a virus known to infect humans, particularly children, though it is not routinely tracked by US health authorities. IDV also plays a significant role in bovine respiratory disease, commonly known as shipping fever, which is the most costly infectious illness affecting North American cattle. This disease can lead to severe conditions such as pneumonia, heart inflammation, and immune suppression, potentially causing mortality in up to two percent of a herd. Despite these animal impacts, Dr. Lednicky noted that IDV has not yet been associated with serious infections in humans. However, previous studies by his team have revealed antibodies to influenza D in as many as 97 percent of cattle workers in Colorado and Florida, suggesting widespread occupational exposure.

The second virus of concern, canine coronavirus (CCoV), is distinct from SARS-CoV-2 but is highly infectious among dogs, particularly in crowded environments like kennels, typically causing gastrointestinal illness. This virus is rarely tested for in humans, leading to a significant knowledge gap regarding its true impact. Despite this, CCoV has been associated with serious infections in humans. In 2021, Dr. Lednicky’s team isolated a canine coronavirus strain from a US medical worker who became ill after traveling to Haiti. In the same year, researchers at the University of Texas Medical Branch identified a nearly identical strain in a child hospitalized with pneumonia in Malaysia. Subsequent detections of the virus in people with respiratory illness in Thailand, Vietnam, and Arkansas demonstrate its capacity to circulate across continents among humans. The lack of routine diagnostic tests means the full extent of CCoV's impact on human health remains largely unknown.

The scientific community's stark warning emphasizes that without stronger surveillance systems, improved diagnostic testing, and dedicated vaccine development efforts, both influenza D and canine coronavirus could silently acquire the ability to spread efficiently between humans. The researchers concluded, "Our knowledge of these viruses is limited. Even so, the available evidence suggests they pose a major threat to public health," echoing broader concerns about the pandemic potential of animal-borne viruses like the Nipah virus currently spreading in parts of India.