By Linda Weiford, WSU News
PULLMAN, Wash. – The new bird influenza spreading in China underscores the need for strong ties between veterinarians and human-health specialists, said Guy Palmer, director of the Paul G. Allen School for Global Animal Health at Washington State University.
The H7N9 bird flu strain is the newest and most visible infectious disease to have emerged from animals to humans, known as zoonosis. Since the virus was first identified in March, it has sickened more than 300 people and killed nearly a third of those infected, according to the World Health Organization.
“By taking an interdisciplinary approach to understanding and controlling influenza and other infectious diseases that originate in animals, we can better predict where zoonotic pathogens are likely to emerge,” said Palmer. “And when they do emerge, we can better detect and contain them.”
This collaboration of expertise, known as “one health,” recognizes that the health of humans, animals and the environment are all interconnected.
Not just China’s problem
With confirmed H7N9 cases rising daily and its geographical range widening from China’s mainland to Hong Kong and Taiwan, international health experts are trying to assess the risk. Live chickens and ducks from poultry markets appear to be the main source of transmission to humans. So far, the virus doesn’t appear to spread from person to person. But as the number of cases surge, the question is, will it evolve so that it can?
There’s a tangle of reasons H7N9 might or might not lead to a large outbreak, with mutations that boost human to human transmission being the most prominent, said Palmer. Other factors include the density of infected poultry and how often humans come into contact with them.
But the flu strain’s fate also rests, in part, on the one-health collaborative effort of experts such as medical doctors, epidemiologists, virologists, molecular geneticists and, yes, veterinarians.
“H7N9 is but one of many pathogens that mix and jump among species, thereby posing a risk to segments of the human community,” said Palmer. “Considering that 60 percent of the infectious diseases that afflict human beings originated in animals, it only makes sense that they be addressed by experts in veterinary and human medicine.”
While many countries, including China, are integrating veterinary health systems, poorer countries lack the resources to do so, he said.
Under the radar
The H1N1 swine flu pandemic of 2009 illustrates how a virus’s threat can grow with inadequate livestock monitoring. The pathogen, believed to have simmered for years in Mexico before emerging to spread person-to-person around the world, killed an estimated 203,000 people -12,000 of them in the United States – according to WHO.
Based on a team of scientists’ analysis of the H1N1 strain, if a better livestock surveillance system had been in place, those numbers probably wouldn’t be so high. The researchers’ study, published in the journal Nature, found that the virus had undergone a series of mutations before crossing from pigs to people (not from eating pork, as some falsely believed). All the while, the virus went undetected as it further mutated, enabling it to spread from one person to another and ultimately from one continent to another.
“… despite widespread influenza surveillance in humans, the lack of systematic swine surveillance allowed for the undetected persistence and evolution of this potentially pandemic strain for many years,” the study’s authors concluded. (See http://www.nature.com/nature/journal/v459/n7250/abs/nature08182.html)
Genetic wild card
Now, five winters after the swine flu pandemic, veterinarians and virologists alike are monitoring the new H7N9 bird flu strain. Surveillance is tricky because, unlike other avian flu strains, infected birds don’t get sick. Humans, therefore, are the proverbial canary in the coal mine.
H7N9, like all flu viruses, has the capacity to mix, or reassort, with other flu viruses to become a patchwork of gene segments that make it more harmful. Certain mutations in H7N9 could alter its ability to readily spread directly among humans, said Palmer, but whether it will evolve in this manner is not known.
“Regardless of which area of expertise scientists bring to the table,” he said, “I think we all regard H7N9 with both unease and respect.”
Contacts:
Guy Palmer, Paul G. Allen School for Global Animal Health at WSU, gpalmer@vetmed.wsu.edu
Linda Weiford, WSU News, 509-335-7209, linda.weiford@gmail.com