If H5N1 turns into a full-blown pandemic, we are currently in chapter one. To prevent chapter two from becoming a reality, the most important tool in our arsenal will be widespread testing. Testing isn’t just about diagnosing people with the virus. Containing the spread of this highly pathogenic bird flu strain in cattle hinges on our ability to detect and track it.
The H5N1 outbreak in dairy cows is widespread and spans multiple U.S. states. Although only one human infection with the virus has been documented, more infections are likely going undetected. Most importantly, unchecked transmission among cattle means the virus is increasingly bumping up against humans. Every human exposure, in turn, provides an opportunity for new mutations that could enable human-to-human transmission.
[time-brightcove not-tgx=”true”]The U.S. Centers for Disease Control and Prevention (CDC) maintains that as of now, the risk to the general public from H5N1 remains low. And indeed, it is entirely possible H5N1 might never turn into a human pandemic.
However, being wrong would be incredibly costly.
We find ourselves in a situation reminiscent of early 2020, when the U.S. stood on the brink of the COVID-19 pandemic and hesitated to take decisive action, restricting testing to only those with epidemiological links to China. Scientists estimate that by early March 2020, less than 1% of SARS-CoV-2 infections in the U.S. were detected by testing. We effectively flew blind straight through chapters one and two of the COVID-19 pandemic.
Today, genomic analyses tell us that bird flu had been circulating in dairy cows for at least four months before it was detected in March 2024. The delay was despite early warning signs of infections on dairy farms in February. The U.S. government cannot afford to repeat the mistakes made at the onset of the COVID-19 pandemic. Though the risk of an H5N1 pandemic may currently be low, the consequences of inaction could be catastrophic, and the benefits of proactive testing far outweigh the short-term costs.
Read More: Why Experts Are Worried About Bird Flu in Cows
Despite the high stakes, government action initially has been slow and uncoordinated. Until mid-April, testing was not only voluntary but restricted to symptomatic animals, with limits on the number of tests per farm. A complicating factor is that responsibility for outbreak control is divided between three federal agencies: the U.S. Department of Agriculture (USDA) for livestock, the U.S. Food and Drug Administration (FDA) for food safety, and the CDC for human health and surveillance. Yet by May, the CDC was aware of only about 30 people who had been tested for bird flu. The CDC has been monitoring data from emergency departments in areas where H5N1 has been found in cattle and has found nothing unusual so far. But if and when infected people show up at the ER, it will be way too late to contain the outbreak at its source.
We must stop flying blind. Regular and widespread testing is our only way to detect H5N1 and stop the virus from spreading.
The recent federal order requiring mandatory testing of dairy cows before they cross state lines is a step in the right direction. But we could be doing more: we should incentivize testing, rather than restricting it. A layered testing strategy that combines waste or wastewater surveillance on the farms, routine testing of pooled milk from the cows, and active surveillance testing of animals and humans—including those without symptoms—is our best hope of stopping the virus from spreading.
The tools and infrastructure for such a testing regimen are already at our fingertips. During the pandemic, the U.S. government spent billions supporting testing and creating an extensive biosurveillance infrastructure. Influenza monitoring via wastewater surveillance has already shown increases in the H5 subtype—the viral group to which H5N1 belongs. In 2024, labs across the U.S. now have PCR machines sitting idle, waiting to be turned back on. And U.S. test manufacturers have efficient automated manufacturing lines capable of producing millions of rapid tests a day.
Read More: Is It Safe to Eat Eggs and Chicken During the Bird Flu Outbreak?
For animal testing, we should accelerate evaluations of both laboratory and point-of-need tests. Testing should include cows, but also pigs, which are known “mixing vessels” for viruses across host species. We should also evaluate different specimens like swabs and cow milk, including the pooling of samples to test more efficiently.
If existing influenza A rapid tests could detect the virus from a drop of contaminated milk, it would be a game changer. Given the sky-high virus loads detected in milk from infected dairy cows, it is possible that a single drop could be enough. But if the tests need to be tweaked, the USDA and FDA should be funding studies to do so now. With H5N1 circulating in herds nationwide, we can quickly assess the effectiveness of these tests and refine our strategies accordingly.
When it comes to human testing, it is laudable that the CDC is now engaging with test manufacturers to develop a widely available H5N1 test. In the meantime, existing authorized rapid tests for influenza A will likely detect H5N1. To confirm, the CDC, FDA, and the National Institute of Health’s Rapid Acceleration of Diagnostics (RADx) program should support evaluations that close that knowledge gap. If these broad influenza rapid tests detect H5N1, we could send any positive influenza A test to a lab for confirmation and evaluation of H5N1 or another virus. This surveillance testing algorithm, which leverages broad influenza tests for initial screening and reserves more specific H5N1 assays for confirmation, followed by rapid sequencing of positives, would allow us to allocate our public-health resources with maximum efficiency. The rapid turnaround times of point-of-need tests would enable infected people to immediately isolate themselves and get influenza antivirals, minimizing the risk of transmission.
The federal government keeps the influenza antiviral Tamiflu as well as personal protective equipment (PPE) in its Strategic National Stockpile. To ensure that tests are similarly available, the government must send a clear demand signal to manufacturers, committing to purchase a substantial quantity of tests, just as they do for antivirals and PPE. This would give manufacturers the confidence needed to ramp up production and create a robust national stockpile. Congress should allocate funding to support these efforts, with the White House’s new Office of Pandemic Preparedness and Response coordinating a unified response across the CDC, USDA, and FDA.
The government must also address the stigma associated with positive test results and provide financial aid and resources to help affected farmers and their workers. Many of the individuals working on dairy farms are undocumented, for example. The current administration should make assurances that offer protection to undocumented workers who agree to test as a part of public-health surveillance testing programs.
Success in public-health prevention is difficult to spot, and success in preventing a pandemic can be misconstrued as a failure or a misappropriation of funds. It’s nearly impossible to recognize the absence of a pandemic that never happens, but would have if not for aggressive and early efforts. However, tracking detections and documenting actions taken will help. The cost of inaction far outweighs the cost of prevention. We risk losing all the lessons learned from COVID-19 if we don’t apply them now.
The good news is that we have the tools to prevent an H5N1 pandemic at hand. But we must be willing to use them, and fast.
