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 | Amid an unprecedented H5N1 outbreak among U.S. dairy cattle, scientists warn that this form of avian influenza was transmitting longer than official reports suggest. (Wendy Martinez/CBC) | | Why dangerous bird flu is spreading faster and farther than first thought in U.S. cattle
Infections could have been 'flying under our radar for months,' researcher says | Lauren Pelley and Amina Zafar | A dangerous type of bird flu virus discovered in the lung of a U.S. dairy cow that didn't show symptoms. Viral particles identified in processed, pasteurized milk. Genetic sequences showing distinct changes in this H5N1 strain that's been rapidly spreading throughout American cattle. Those were just a handful of the rapid-fire developments this week as an unprecedented H5N1 outbreak among U.S. dairy cattle continued to evolve. Scientists now warn this form of avian influenza is likely more widespread in cows, and was transmitting for longer than official reports suggest. And while American officials are ramping up testing — all in an effort to keep sick cows from being moved between states — others say we're already several steps behind the spread of a disease that could pose a major threat to human health. Michael Worobey, a researcher from B.C. who's now head of the department of ecology and evolutionary biology at the University of Arizona, said these cattle infections may have been "flying under our radar for months," providing ongoing opportunities for this virus to acquire adaptations that could lead to a flu pandemic. "I think, in many ways, this is the biggest news story in the world right now."
Tracing the root of outbreak
After the U.S. Department of Agriculture posted more than 230 genetic sequences from the country's growing H5N1 outbreak last Sunday, Worobey was among the scientists racing to analyze the complex set of data. The sequences were from cattle — amid an outbreak impacting more than two-dozen herds across nine U.S. states — but also several bird species, cats, skunks and raccoons. It's possible that local birds passed the virus to local farms, in different states, and they're all spreading a genetically similar lineage, he said. But Worobey believes what's far more likely is that the cattle outbreak has a single origin point. In an interview with CBC News, he outlined H5N1's evolutionary tree, with a distinct branch of sequences linked to cattle. All those sequences share the same mutations, Worobey added. "This is the hallmark of a single jump, that's at the root of this outbreak," he said. And that jump likely occurred earlier than the first known cattle infections reported in late March. | |  | Thermometers are seen atop a small-scale pasteurizer. The discovery of viral RNA in milk in the U.S. doesn't actually mean it can make people sick. (Toby Talbot/The Associated Press) | | A single introduction could have happened as far back as November or December, with a distinct lineage of H5N1 then spreading undetected for months, Worobey said. He added missing details in the U.S. data dump — including exact cattle locations and dates — make it tough to know for sure.
The cattle sequences also contain "at least two distinct mutations" that are known for increasing the risk of a flu virus infecting and transmitting in humans, Worobey added.
"We just are producing more and more [opportunities] for evolution to arrive at something that can transmit in humans, and potentially kill a large proportion of them," he said.
Milk discoveries
What's not yet clear is how, exactly, the virus is spreading among cattle, though several scientists told CBC News that possibilities include close contact between cows being transported between states or contaminated milking equipment.
"If the cattle indeed have [infection] in the udders, then transmission could be through milking equipment," said Michelle Wille, a senior research fellow with the University of Melbourne's Centre for Pathogen Genomics and the department of microbiology and immunology.
"A number of infected states have indicated that [avian flu] was detected in dairy herds that recently received cattle from Texas — so transport of cattle is likely playing a role in spread."
At this point, it's still unclear how the virus is "sustaining transmission" in cattle populations, added virologist Angela Rasmussen, from the University of Saskatchewan's Vaccine and Infectious Disease Organization.
It's also likely the virus is being transmitted even when cows aren't showing symptoms — which have so far been mild, including low appetite and reduced milk production — several scientists agreed.
Read more from CBC Health's Lauren Pelley and Amina Zafar on why this week's dual discoveries of H5N1 in the U.S. concerns scientists on both sides of the border.
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Cross-Canada health news from CBC |  | Makeshift slaughterhouse in a residential garage points to growing concerns about illicit meat sales | CBC Edmonton |
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| | Mammograms are routine. For people who use wheelchairs, they're anything but | CBC Montreal |
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| | Fewer medical school graduates choosing family medicine, Ontario doctors warn | CBC Toronto |
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 | Nina Gomes recovers a discarded plastic bag from ocean waters in Rio de Janeiro, Brazil, in March. Some doctors and scientists are calling for reduced plastic production to protect health and the environment. (Bruna Prado/The Associated Press) | | What are microplastics doing to human health? Scientists work to connect the dots | | Plastic serves as a building block for our food packaging, water pipes, rubber tires and synthetic fabrics. But plastic also litters waterways, soil and air so humans and other animals wind up taking in tiny versions with unknown consequences.
People inadvertently ingest microplastics from what we eat, drink and breathe. Some scientists fear exposure to microplastics could increase vulnerability to heart disease, cancer and other illnesses. They're working to connect the dots between microplastics and any health hazards.
At this week's United Nations' global summit on plastic pollution in Ottawa, delegates are working toward a treaty to address plastics from production to use and disposal.
Dr. Leonardo Trasande directs the NYU Langone Center for the Investigation of Environmental Hazards and is attending the meeting in Ottawa. Trasande became interested in the hormone hacking or endocrine disrupting properties of plastics when he was resident in pediatrics and seeing patients with diabetes.
"Microplastics are in many ways a harbinger of the much bigger problem," Trasande said.
While possible links between microplastics and illnesses like Type 2 diabetes are not definitive, researchers are exploring some concerning hints.
Read more from CBC Senior Health Writer Amina Zafar on heart damage and other health effects associated with microplastics. |
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Trending research | | | Developmental Milestone Attainment in US Children Before and During the COVID-19 Pandemic | JAMA Pediatrics |
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| | | | Influence of Role Expectancy on Patient-Reported Outcomes Among Patients With Migraine: A Randomized Clinical Trial | JAMA Network Open |
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Hospital use by patients experiencing homelessness highlighted | THE NATIONAL | Canadians experiencing homelessness have complex health needs. They also stay nearly twice as long in hospital at a cost over double the national average, in part due to the housing crisis, finds a sweeping new report from the Canadian Institute for Health Information. Senior Health and Medical Reporter Lauren Pelley reports on what one hospital is doing to counter the trend. | |
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THE BIG NUMBER | 154 million | | Good news: It's estimated 154 million deaths were averted by global immunization since 1974, researchers from the World Health Organization (WHO), United Nations Children's Fund (UNICEF) and partners say.
Infants benefited the most with 101 million saved over the past 50 years, according to UNICEF.
Immunization offered the single greatest contribution of any health intervention to help babies. Other factors that helped included lower poverty and better nutrition, cleaner air and water and readily available antibiotics.
The vaccination programs also provide an opportunity to provide other life-saving care, such as nutritional support, screening for illness and distribution of bed nets to protect people from malaria and other diseases spread by mosquitoes.
The study, to be published in The Lancet, was commissioned on the 50th anniversary of the WHO’s Expanded Programme on Immunization to wipe out smallpox.
Read more from UNICEF. | |
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Stories we found interesting this week | | Doctors Combined a Heart Pump and Pig Kidney Transplant in Breakthrough Surgery | Wired |
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| | Massive amounts of H5N1 vaccine would be needed if there’s a bird flu pandemic. Can we make enough? | STAT |
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|  | New episode dropped April 25
While we tend to think rest is the key to recovering from an injury, experts recommend keeping the body moving, if possible, but at a lower intensity.
Sport medicine physician Dr. Laura Cruz explains why "motion is lotion" and provides some low-impact exercises that can help our bodies more easily recover.
Play on CBC Listen |
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|  | New episode airs April 27 and 28
Attracting a family doctor to work in a community today is challenging, with fewer physicians choosing family medicine. To stand out, Cheryl Gnyp, the recruiter for the city of Castlegar, B.C., uses the board game Operation as part of her 10-minute sales pitch to potential recruits at conferences. It can take years before a doctor starts working in the community, but she’s in it for the long haul.
Tune in on CBC Listen |
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| | Thanks for reading! You can email us any time at secondopinion@cbc.ca with your comments, questions, feedback or ideas. | |
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