To fight bird flu, lock up the cows

Bird flu could be entering a dangerous new phase. The risk of any given person becoming ill or dying remains low, but the risk of this virus mutating into the next human pandemic is high enough to warrant action. That starts with much more aggressive measures to test and contain infected dairy herds.

“If we really don’t want this to get to people, we need to do something about the cows,” says Seema Lakdawala, an immunologist at Emory University School of Medicine. And she's right.

Every time the virus reaches a new host — bovine or human — it creates billions of new copies of itself, increasing the chances of encountering the combination of mutations it needs to trigger the next human pandemic.

Since the virus known as H5N1 was discovered in dairy cows in March, it has continued to spread across the country, appearing in 200 herds in at least 14 states. In Texas, a wastewater study in September found the virus in 10 out of 10 samples. Scientists cannot be sure whether these signals come from animals or humans.

So far, only 14 people have tested positive for H5N1 in the U.S., but very little testing is taking place. A hospital patient in Missouri tested positive in September despite no known contact with birds or cows. A household contact of this person also tested positive. Two health care workers who were in contact with the hospitalized person reported flu-like symptoms. (The workers recovered before they could be tested.)

H5N1 has been killing domestic chickens and wild birds and threatening humans since the 1990s. The current outbreak dates back to late 2022 or early 2023, when it began killing mammal species around the world, including seals, sea lions, grizzly bears, foxes, cats, mice and minks.

In previous human outbreaks, the mortality rate from H5N1 was a staggering 50 percent. This latest variant appears to be milder, but as we have seen with COVID, even a disease that is less than 1 percent fatal can have devastating consequences if it becomes widespread.

There are still large gaps in scientists' knowledge. They still don't know whether infected cows become immune or can become reinfected. They don't know whether some infections may be asymptomatic. They don't know how long sick cows can spread the virus.

We urgently need answers to these questions. That starts with a more aggressive stance from the U.S. Department of Agriculture, the Centers for Disease Control and Prevention and state health officials.

Most of the monitoring is currently being done through testing of bulk milk, Lakdawala said. While some infected cows show symptoms, others may spread the disease silently. Farmers whose bulk milk tests come back positive need the tools to test each individual cow to isolate the infected animals and prevent further spread.

Lakdawala said dairy farms often use machines to milk cows, but they are not always disinfected. Research by her group showed that the virus remains on milking equipment for long periods of time. She says contaminated equipment is likely one of the main ways it spreads among cows.

She's also concerned about the contaminated milk farmers are sending down the drain. “We have reports that these cows can contain up to 100 million infectious virus particles in a small milliliter of milk,” she said. And dairy farmers are pouring out gallons. The infectious milk goes into manure lagoons, she said, where solids are separated and liquids can end up in irrigation fields. In some cases, dead cats are found in these fields. (Cats are known to be susceptible to H5N1).

It's possible to kill the virus by treating milk with high heat, but farmers don't always have the means to do so, she said. That's why her lab is working on more cost-effective methods to disinfect infectious milk before it is thrown away.

And cows are still being transported across the U.S., sometimes without adequate testing, she says. “We need a temporary stay-on-farm order where cattle are simply not moved while we figure out which cattle are infected,” she said.

More testing of people would also help monitor the situation, said epidemiologist Jennifer Nuzzo, director of the pandemic center at Brown University. “We are not getting ahead of the problem.”

“The fact that farmworkers continue to become infected in the course of their work means this is a serious public health situation,” she said. “I don’t think we should wait for a farmworker to die before we look at protecting them.”

The risk of a more dangerous variant emerging will increase as the flu season begins in the fall. Different influenza viruses can infect the same person and exchange genetic material. With the ability to spread easily from person to person, something new could emerge — “our worst-case scenario,” she said.

If this virus were spreading on dairy farms in China and not the U.S., we would demand more testing, more transparency about the extent of the disease and the details of these mysterious cases in Missouri, she said. “I have been assured by the CDC and local public health that they have conducted contact tracing [but] There is no data on it,” Nuzzo said. If we want other countries to be transparent with us, “we have to be transparent.”

Currently, scientists cannot quantify the likelihood of this virus causing the next pandemic. However, the risk increases the longer the virus circulates in pets. It's time to lock up the cows.

©2024 Bloomberg LP Distributed by Tribune Content Agency, LLC. FD Flam is a Bloomberg Opinion columnist covering science. She is the host of the “Follow the Science” podcast.

This column does not necessarily reflect the opinion of the Bloomberg LP editorial team or of Bloomberg LP and its owners. GovernThe opinion columns reflect the views of their authors and not necessarily those of Govern's editors or management.