The first step in combating any infectious disease outbreak is detection. Without widespread testing, health officials have little sense of who is infected, when to treat patients and how to monitor their close contacts.

In that sense, the bird flu outbreak plaguing the nation’s dairy farms is spreading virtually unobserved.

As of Monday, the virus had infected 157 herds in 13 states. But while officials have tested thousands of cows and are monitoring hundreds of farmworkers, only about 60 people have been tested for bird flu.

Officials do not have the authority to compel workers to get tested, and there is no way for workers to test themselves. In the current outbreak, just four dairy workers and five poultry workers have tested positive for H5N1, the bird flu virus, but experts believe that many more have been infected.

Five people who work at a poultry farm in northeastern Colorado have tested positive for the bird flu, the Colorado public health department reported July 14. (One of the cases awaits confirmation by the federal Centers for Disease Control and Prevention.) This brings the known number of U.S. cases this year to nine.

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The workers were likely infected by chickens, which they had been tasked with killing in response to a bird flu outbreak at the farm. The endeavor occurred amid a heat wave, as outside temperatures soared to 104 degrees Fahrenheit.

“The barns in which culling occurs were no doubt even hotter,” said CDC principal deputy director Nirav Shah at a July 16 press briefing. Wearing N95 respirators, goggles, and other protective gear was a challenge. Industrial fans whipped feathers around the facility that could have carried the virus, Shah added.

In this environment, the farmworkers collected hundreds of chickens by hand and placed them into carts where they could be killed by carbon dioxide gas within two minutes.

Dairy farmworkers often spend 10 to 12 hours a day milking dairy cattle in crowded, wet environments. They are in constant, intimate contact with unpasteurized cow milk, a known carrier of H5N1, the viral strain of bird flu that jumped from poultry to cows back in March.

But despite being the most exposed population to the virus, farmworkers are also offered few protections. To prevent the spread of bird flu among the general public, experts say we need to first protect the health of farmworkers.

“I don't want us to ignore what is happening right now, which is that farmworkers are getting infected with this virus,” said Jennifer Nuzzo, an epidemiologist at Brown University.

As bird flu spreads among dairy cattle in the U.S., veterinarians and researchers have taken note of Finland’s move to vaccinate farmworkers at risk of infection. They wonder why their government doesn’t do the same.

“Farmworkers, veterinarians, and producers are handling large volumes of milk that can contain high levels of bird flu virus,” said Kay Russo, a livestock and poultry veterinarian in Fort Collins, Colorado. “If a vaccine seems to provide some immunity, I think it should be offered to them.”

As bird flu spreads among dairy cattle in the U.S., veterinarians and researchers have taken note of Finland’s move to vaccinate farmworkers at risk of infection. They wonder why their government doesn’t do the same.

Excerpt: "We're flying blind," said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. With so few tests run, she said, it's impossible to know how many farmworkers have been infected or how serious the disease is. A lack of testing means the country might not notice if the virus begins to spread between people — the gateway to another pandemic.

Excerpt: And while the federal government has made efforts to try to bolster the stockpile of supplies, “there hasn’t been a lot of transparency. It’s hard to gauge the sufficiency of it,” said Jennifer B. Nuzzo, director of the Pandemic Center at the Brown University School of Public Health.

Guest essay by Jennifer Nuzzo, excerpt: How worried you should be about H5N1, the bird flu virus spreading on dairy farms in the United States, depends on whom you are.

The Centers for Disease Control and Prevention has described the current H5N1 risk to the general public as low. The risk that the virus poses is tempered by the fact that it doesn’t spread easily among people — yet.

Right now public-health experts have the difficult task of urging authorities who can do something about H5N1 to take action, while maintaining public trust. Americans have just been through a pandemic that resulted in over one million U.S. lives lost. They may feel weary of more bad news or fear-based messaging. Communicating that while the threat level for most people is low, but if nothing is done it could become quite high, is not easy but is important.

Excerpt: “The concern about H5N1 has always been there,” said Dr. Jennifer Nuzzo, professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health. “But in the last couple of years, [the virus] started doing things that have been a bit unusual.”

“We’ve seen this virus start to infect mammals and a wide range of mammals,” she said, pointing at the different outbreaks throughout the world. “That’s a concern because humans are mammals, and so mammals are more like us than birds are.”

But what makes this recent outbreak the most concerning for Nuzzo is that the virus is now capable of infecting cows. “Cows are mammals that humans have a lot more contact with than all the other mammals that we’ve seen get infected,” she said.

Analyses by Jennifer Nuzzo, Jorge Ledesma, and others.

Excerpt: “My highest level of concern right now is for the workers on the farms, who we know are being exposed to this virus and we know are already getting sick with this virus,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “We need to be talking more about protecting the workers who are in harm’s way today.”

Excerpt: Seth Berkley, a longtime and widely respected global health leader, said Thursday that it has been “shocking to watch the ineptitude” of the U.S. response to the avian influenza outbreak among dairy cattle, adding his voice to a chorus of critics.

In a presentation in London about vaccine development, Berkley, the former CEO of Gavi, the Vaccine Alliance, raised the issue of H5N1 bird flu when discussing whether the world was ready for another pandemic following its experience with Covid-19.

Webinar hosted by USC Anneberg Center for Health Journalism which featured Jennifer Nuzzo as a panelist.

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Excerpt: “The Centre for Disease Control laboratory is one of a few labs where eye specimens can be tested for H5N1 – this needs to be fixed, easier access to eye swab testing is needed to protect and diagnose farm workers,” said Dr Jennifer Nuzzo, Director of the Pandemic Centre and Professor of Epidemiology at the Brown University on X (formerly Twitter).

Excerpt: Jennifer Nuzzo, director of the Pandemic Center at Brown University’s School of Public Health, said she wished other states were looking for H5N1 cases as aggressively as Michigan is.

“If there’s any takeaway from this finding it’s that this is probably the tip of the iceberg because this is the one state that we know of that has done the most in terms of testing on farms of both cows and also monitoring workers that are on the farms where they found cattle infections,” she told STAT.

Excerpt: Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health, said she was glad to hear that the CDC is pushing for continued flu surveillance.

“So many of our data points and response options are predicated on being able to find cases, and there are currently many holes in our ability to do that,” Nuzzo said.

Excerpt: “The more this virus circulates, the more there is a chance for mutations,” said Dr. Jennifer Nuzzo, a professor of epidemiology who directs the Pandemic Center at the Brown University School of Public Health. And more mutations could mean a bigger risk of the virus becoming highly infectious among more people.

Excerpt: “We have no idea if this virus is going to evolve to become a pandemic strain but we know today that farmworkers are being exposed and we have good reason to think that they are getting sick,” said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health

Here & Now's Peter O'Dowd speaks with epidemiologist Jennifer Nuzzo about the bird flu that has recently sickened dairy cows in several states but so far only one dairy worker in Texas.

Professor Jennifer Nuzzo, epidemiologist and director of the Pandemic Center at the Brown University School of Public Health, joins host Megan Hall for a timely update on the recent outbreaks of H5N1 Bird Flu.

Jennifer Nuzzo is a co-author of this piece, published in PLOS Global Public Health, featuring work for the Exemplars in Global Health program.

Opinion piece cowritten by Jennifer Nuzzo.

Excerpt: The discovery of bird flu virus particles in milk has moved the federal government to take more aggressive action to prevent the further spread of H5N1 on dairy farms. The Agriculture Department has rightly issued new testing recommendations meant to keep the virus from spreading across state lines. But this additional testing will do little to address the primary threat that H5N1 poses to humans: the infection of farmworkers. Our failure to protect them threatens their health and gives the virus an opportunity to evolve into a greater threat to people, including those who live far from dairy farms.

Excerpt: "It does feel like Ground Hog Day," said Jennifer Nuzzo, who heads Brown University's Pandemic Center. "We still seem to be stuck in reactive mode. We shouldn't be waiting for evidence that the virus is devastating us. We should be trying to act now to prevent the virus from devastating us."

Excerpt: But it's still not clear exactly where the flu virus has spread or what it's capable of, said several experts, including Jennifer Nuzzo, a professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health.

"Our surveillance is inadequate to know where this virus is and where it isn't, which is critical for protecting farmworkers and people involved in the dairy industry ‒ but also important for staying ahead of this virus to prevent a future pandemic," Nuzzo said.

Excerpt: “More testing is better,” said Jennifer Nuzzo, an epidemiologist and director of Brown University’s Pandemic Center. “But in many ways this policy is very leaky in terms of how much virus it will allow to move. And because we still don’t know what’s driving transmission between cows, we should not pin our hopes on this policy making a major dent in the infections we’re seeing.”

Excerpt: “Our job right now is to protect farmworkers,” said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health. “We can’t do that unless we know where the virus is or where it isn’t.”

Excerpt: Some public health experts are concerned about how long that testing is taking — and the lack of transparency thus far about the government’s findings. Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health, questioned why the FDA did not immediately say it would test milk products and expeditiously culture any potential virus fragments found.

“Just from a government credibility standpoint, being transparent about what you’re doing, it’s important,” Nuzzo said.

Excerpt: To really understand the scale of spread as well as possible mechanisms of viral transmission, it’s necessary to conduct widespread testing of animals with and without symptoms, said Jennifer Nuzzo, an epidemiologist and director of Brown University’s Pandemic Center. “If we’re only testing cows with outward symptoms, we’re missing infections in those without.”

Excerpt: So let's start with the latest update, particles of this virus found in commercial pasteurized milk. How concerned should the everyday consumer be?

Dr. Jennifer Nuzzo, Brown University School of Public Health: I don't have any reason to be concerned at this point.

Finding evidence of genetic material, which is what the test results told us, by itself is not alarming. In order to know if the virus will infect us, we have to do a different kind of test. And this test was not that. They're actually undergoing those tests now.

But I don't have any reason to think that we will be harmed, because we use pasteurization. And I have no reason to think that the H5N1 virus is any different from all the other pathogens that we think could be in milk. Pasteurization doesn't remove the genetic material of those pathogens, but it changes the pathogens and either kills or it activates them, so that they can't infect us...

Excerpt: The Food and Drug Administration on Tuesday said it had been testing milk samples throughout the dairy production process and confirmed the detection of viral particles “in some of the samples,” but declined to provide details.

The presence of genetic fragments of the virus in milk is not unexpected. Pasteurization typically works to inactivate pathogens, said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. Pasteurization generally does not remove genetic material, but it typically renders pathogens unable to cause harm to people, Nuzzo said.

Excerpt: For decades, public health experts have warned of the danger of H5N1, also known as the avian flu, crossing over to humans. That fear became a reality when earliest this month, a dairy farm worker in Texas tested positive for the highly pathogenic avian influenza. This is the first reported cow-to-human spread of the virus. The U.S. has only ever recorded a handful of cases but there is mounting concern that mutations in the virus will allow it to spread to more mammals and possibly, more people. Are we ready for an influenza pandemic of this kind? Joining us today on AirTalk to talk about this latest outbreak and the threat it poses to humans is Jennifer Nuzzo, Professor of Epidemiology and Director of the Pandemic Center at Brown University.

Brown University Pandemic Center leader honored for outstanding humanitarian efforts and achievements in the field of global public health

Excerpt: For a virus to have pandemic potential, it needs to be able to pass easily from person-to-person. H5N1 does not have the ability to do so, but scientists fear it could develop this feature.

“The bigger picture is that this virus is not cooling off,” CFR Senior Fellow Jennifer Nuzzo told Politico. “We’ve been worrying about this virus for twenty years, more than twenty years. And in the last year, it has really been remarkable in how far across the globe it has been spreading, and how many species it’s been affecting.”

Pandemic Center director Jennifer Nuzzo, DrPH, was interviewed on the April 4, 2024 edition of PBS NewsHour

Excerpt: “The bigger picture is that this virus is not cooling off,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “We’ve been worrying about this virus for 20 years, more than 20 years. And in the last year, it has really been remarkable in how far across the globe it has been spreading, and how many species it’s been affecting.”

Excerpt: "I worry a little bit that the perceived speed with which we were able to develop safe and effective vaccines has given people unrealistic expectations," said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health. "Nevertheless, we did something remarkable, and we proved to ourselves that we can do hard things," she added.

A new exercise, highlighting the ability of Artificial Intelligence (AI) to meet pandemic threats, will be tested this week at the Munich Security Conference.

Excerpt: If this change takes place, it shouldn't be interpreted to mean that COVID-19 is less contagious, says Jennifer Nuzzo, an epidemiologist and director of the Pandemic Center at Brown University School of Public Health.

"The science of COVID has not changed," Nuzzo says. If you test positive for COVID-19, you're likely contagious for a few days at least and risk spreading the coronavirus to others.

Excerpt: The proposed recommendations also seem not to take into account older Americans, or those who are immunocompromised or otherwise at risk of severe outcomes from Covid, said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health.

Dr. Nuzzo said she has an aunt with cancer who had twice contracted Covid in a health care facility. “I do feel for people who now feel even less protected,” she said.

At the very least, the C.D.C. should advise that people who end isolation after one fever-free day also wear N95 masks or the equivalent when leaving their homes, she added.

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New office will expand impact and connect current and future public health leaders with national and global policymakers