Health officials are making a renewed call for vigilance against bird flu, as the spread of the H5N1 virus continues to be a concern. However, experts are puzzled over the recent halt in reports of new human cases. Questions arise: Have government budget cuts weakened the search for these cases? Are immigrant farm workers, who have previously accounted for a significant number of U.S. cases, more hesitant to seek testing due to fear of deportation during the Trump administration? Or is this simply a natural decline in infections? As Jennifer Nuzzo, director of the Pandemic Center at Brown University, commented, “We just don't know why there haven't been cases. I think we should assume there are infections occurring among farmworkers that are just not being detected.”
The H5N1 bird flu virus has been spreading widely among wild birds, poultry, and various animals globally for several years. Starting early last year, it became a significant issue in both humans and cows within the U.S. In the last 14 months alone, there have been reports of infections in 70 people in the U.S., with most cases involving workers on dairy and poultry farms. Although one individual died, the majority of those infected experienced mild illnesses. The latest confirmed cases reported by the Centers for Disease Control and Prevention (CDC) occurred in early February in Nevada, Ohio, and Wyoming.
California had previously been identified as a hotspot, accounting for three-quarters of the nation’s infections in dairy cattle. However, recent data indicates a significant decline in testing and reported cases among humans. While at least 50 people were tested each month in late 2024, only three individuals were tested in March, one in April, and none so far in May, according to state records. Overall, the state has confirmed H5N1 infections in 38 people, with no new cases reported after January 14.
During a recent call with U.S. doctors, a CDC official noted the seasonality of bird flu, suggesting that cases typically peak in the fall and early winter. This seasonal pattern may be influenced by the migration of wild birds, which are primary carriers of the virus. Consequently, it is possible that the U.S. is experiencing a natural, albeit temporary, decline in cases. Infectious disease expert Michael Osterholm from the University of Minnesota expressed confidence that a severe human infection requiring hospitalization would not go unnoticed. Furthermore, a monitoring system assessing viruses in sewage and wastewater has indicated limited activity recently.
Recent USDA data showing a decrease in animal detections aligns with the CDC's statement that the reduction in human cases is not surprising. However, some experts, including Dr. Gregory Gray, believe that the lack of new cases does not signify a hidden issue. While Gray is not concerned about the absence of reported cases, Osterholm and others argue that milder infections could be going undetected, which raises concerns about the diminishing effort to identify them.
Concerns regarding government cuts affecting bird flu monitoring have been voiced by experts. Resignations at the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) could hinder the government's ability to monitor bird flu effectively. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, noted that three of 14 experts accepted deferred resignation offers at the National Animal Health Laboratory Network, which plays a critical role in responding to disease outbreaks. This is part of a larger trend where over 15,000 USDA staff accepted similar offers.
Meanwhile, the FDA's Veterinary Laboratory Investigation and Response Network has also experienced staff reductions, impacting investigations of animal diseases related to contaminated pet food. Recent incidents of cats in various states becoming sick and dying after consuming raw pet food contaminated with H5N1 have raised additional concerns.
Angela Rasmussen, a virologist at the University of Saskatchewan, pointed out that the decline in targeted surveillance has been particularly sharp since the Trump administration took office. She raised concerns that immigrant farm workers may be too fearful to report exposures or seek testing due to fears of deportation. “I can’t argue with anyone who would be risking getting shipped to a Salvadoran gulag for reporting an exposure or seeking testing,” she remarked.
The CDC continues to characterize the risk of bird flu to the general public as low; however, the risk is elevated for individuals working with cattle and poultry or those in contact with wild birds. A recent agency assessment indicated a moderate risk that currently circulating strains of bird flu could lead to a future pandemic. Nonetheless, the CDC emphasized that similar concerns have been raised about emerging bird flu strains in the past. Ongoing research efforts are critical in understanding and mitigating the risks associated with this virus.
Scientists at Texas A&M University are actively collecting blood samples from dairy workers across multiple states to assess for signs of past H5N1 exposure. Led by David Douphrate, a workplace health and safety expert, this year-long study is funded by a nearly $4 million grant from the CDC and is expected to conclude in July. Douphrate expressed satisfaction with the participation of dairy producers and workers in the study.
Moreover, similar surveillance efforts are urgently needed for domestic cats, as highlighted by Kristen Coleman, a researcher at the University of Maryland at College Park. Coleman has released a paper reviewing bird flu infections in cats from 2004 to 2024, noting that barn cats that died after drinking raw milk were among the first signs of dairy cows becoming infected in 2024. The USDA has confirmed over 120 domestic cats infected with H5N1 across the U.S., primarily in cases where the cats have died. The research on milder infections and the possibility of recovery in cats remains limited, and funding for this research is uncertain.
As Coleman stated, “It’s easy to downplay something because that’s usually what humans do. But what we really need to be doing is ramping up.” Efforts to monitor and understand bird flu are crucial in ensuring public health safety and preparing for future outbreaks.
