CORVALLIS, Ore. – An Oregon State University scientist is heading a multinational team studying how to anticipate and curb the next disease outbreak before it blows up into a global epidemic.
Funded by a new $2.5 million grant, OSU plant pathologist Christopher Mundt and his team are probing infectious diseases of humans, animals and plants that have a distinctive trait in common: the capability of the pathogen – whether virus, fungus or bacterium – to transmit itself over long distances. This pattern, he said, characterizes diseases like avian flu, which have produced continental-scale epidemics.
“Our goal is to develop rules of thumb for identifying and controlling diseases that have this long-distance dispersal capability,” said Mundt. “We don’t have the scientific manpower to create detailed models of every potential epidemic. So a generalized set of control strategies would be vital in policy planning during the early stages of an outbreak.”
Mundt, a professor in OSU’s College of Agricultural Sciences, is partnering with scientists from Kansas State University, North Carolina State University and two universities in England on the five-year project, which is being funded by several organizations.
As people and pathogens move freely around a warming world, pandemic diseases increasingly threaten public health and global economies, according to the National Science Foundation, one of the project’s funding agencies. The World Health Organization calls infectious-disease epidemics “contemporary health catastrophes.”
For 15 years Mundt and his OSU colleagues have been studying stripe rust, a fast-spreading fungal disease that damages wheat, in experiments on commercial farms in central Oregon’s Jefferson County.
The new study will incorporate findings from this ongoing work. Mundt and his team will also analyze data from two real-life 2001 epidemics: foot-and-mouth disease in Britain, caused by a virus; and sudden oak death, which started in California and spread to southern Oregon. That disease is transmitted by a water mold called Phytophthora ramorum.
The researchers will also study historical outbreaks of animal and human viral diseases spread by insects, such as West Nile, Rift Valley fever and Japanese encephalitis. Finally, they will use modeling and field experiments to test strategies for controlling epidemics, including vaccination, drug therapy, quarantines, and eradicating of host organisms around centers of infection.
Pathogens that can disperse over long distances are dubbed “fat-tailed” organisms, said Mundt – a reference to the shape of their spread pattern on a graph. A fat-tailed curve, he explained, looks like a hill with a long tapering slope off to the right. The taper represents the rapid movement of the disease “front” through space over time.
In contrast, the curve of a slower disease, like measles, looks more like a hill without the tapering slope. The downhill plunge represents the disease’s decline with distance at a constant, linear rate.
It’s been assumed, Mundt said, that most epidemics follow the same linear pattern as measles. “But that wasn’t what I was seeing in my stripe-rust experiments.” Instead, the outbreaks accelerated as they pushed out from the epicenter, and the larger the initial infection site, the faster the acceleration rate.
Mundt and his OSU team have also experimented with control techniques to curb the spread of stripe rust, including ring culling – eradicating the host organism (in this case, the wheat) in a ring around the infection to halt its spread.
“There’s been a lot of interest in how big that ring should be,” Mundt said. “Our field studies and modeling are both suggesting that what matters more is how quickly you get on it. That’s because of that accelerating disease front.”
The foot-and-mouth epidemic in Britain was halted by ring culling, he said, but it was a drastic and controversial measure, resulting in the slaughter of some 4 million head of livestock. Foresters in southern Oregon also used ring culling to slow the spread of sudden oak death, cutting and burning trees and shrubs around centers of infection.
“If what we’re seeing is correct,” Mundt said, “it tells us we will need to put more effort into initial surveillance and containment of these fat-tailed organisms, so we can perhaps avoid drastic measures later.”
The research is funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture in collaboration with the National Science Foundation, the National Institutes of Health and the U.K.’s Biotechnology and Biological Services Research Council.