Researchers Race to Figure Out the Flu’s Wild Origins—Before It’s Too Late

By Jonathan Runstadler, professor of infectious disease and global health, Cummings School of Veterinary Medicine, Tufts University

In the early 20th century, the  was infectious disease. Epidemics erupted with little warning, seemingly out of the blue. When the “Great Influenza” struck in 1918, it  in American cities and spread like wildfire around the globe. My great aunt, still a teenager, and living in the San Francisco area, was one of its estimated .

Neither public health authorities nor medical researchers understood that it was a virus that caused the 1918 pandemic—most of the world at that time didn’t even know what a virus was. A century later, , thanks to public health efforts and improved medical technology and expertise. . Nonetheless, 100 years later, infectious disease specialists like me still fear the emergence of viral diseases that we will not be able to control, including influenza.


Identifying the Invisible, Infectious Virus

Until well into the 1930s, the  was mistakenly thought to be a bacterial infection, with Haemophilus influenzae commonly blamed. This bacterium is a pathogen in its own right and may have contributed heavily to the 1918 pandemic’s death toll—but it was a secondary infection in many of the severe cases, not the original cause of victims’ illnesses.


The answer, it seems, lay at least in part in people’s naiveté about the relationship between animals, the environment and human disease. In 1918, veterinarian J.S. Koen . Yet, it wasn’t until 1931 that researcher Richard Shope identified a filterable agent, smaller than bacteria, as the cause of the disease in pigs and demonstrated the transmission of . That work spurred the description of human influenza virus in 1933.

The tools of molecular biology, including , developed through the latter half of the 20th century, finally helped open the vault on the origins of the 1918 pandemic. In 2005, through a combination of sleuthing and sequencing of the viral genome,  and a team of researchers pieced together the , using viruses collected from the corpses of soldiers and other bodies preserved in the Arctic permafrost who died during the pandemic.


Natural World a Reservoir for Human Disease


As researchers have sequenced the influenza viruses found in ducks and other birds, as well as people, swine and other animals, a picture of viral ecology based in nature has come into focus. Birds serve as a reservoir for a vast diversity of influenza viruses to which all the major human pandemics . People were largely unaware that at the same time as the 1918 flu pandemic, pigs were sick with the disease and influenza viruses were also causing ongoing fowl plague epidemics. Exactly how and where the 1918 virus  remains controversial. But the realization that influenza virus happily exists in a wild animal reservoir has influenced the way scientists study flu—and moreover, emerging disease of any sort.

This understanding is also part of what underlies the One Health movement—the concept that the health of humans is entwined with the health of animals and of the environment. The  and  initiatives are forging collaborations between medical doctors, veterinarians, ecologists, environmental researchers and those in many other fields to describe the connections among environmental change, animals and human health.

Watching the Wild World to Protect Human Health

We now know that a full . In the past 20 years, that awareness has resulted in stronger efforts at  and the identification of several other influenza viruses that threaten public health. In my lab’s work, we endeavor to describe the ecology and natural history of influenza virus in animals to understand how new viruses arise and what the risk is of spillover into new hosts where they may cause disease.

For instance, human activity—such as the existence of open landfills, habitat destruction or farming practices—can attract or force animals to crowd into spaces they normally may not. When interactions between species and the environment are disrupted in this way, how does it affect the circulation, evolution and movement of influenza viruses or other pathogens that those animals host? Changes in the ecology of pathogens in the wild are what most frequently leads to spillover into human populations and disease outbreak.



That information may be crucial in identifying and containing the next pandemic virus. The One Health community’s experience with influenza has informed how scientists try to understand and prevent the spread of other diseases, including ,  and . Researchers were quick to chase after the animal source of SARS and are still hard at work to identify reservoir hosts and understand the disease ecology of the Zika and Ebola viruses.



This article was originally published on The Conversation. Read the .
