At the start of 2025, many Americans were concerned about escalating egg prices and the risk of bird flu transmission from wildlife and livestock to humans. This issue resurfaced in the news after Moderna revealed that the Trump administration had decided to cancel a substantial contract, worth $766 million, aimed at developing a bird flu vaccine for humans.
In the past 15 months, the U.S. Centers for Disease Control and Prevention (CDC) recorded 70 human cases of bird flu across 13 states. The latest cases were documented nearly four months ago in February—specifically in Nevada, Ohio, and Wyoming.
California had been particularly affected, with 38 human infections reported by January. Since then, the state hasn’t seen any new cases. The Associated Press noted that testing for the virus has significantly declined; in contrast to the over 50 tests per month in 2024, only three were conducted in March, one in April, and none in May.
A CDC spokesperson stated that the recent drop in new animal infections had decreased the exposure risk for people, and thus, human cases have also fallen.
While it seems the H5N1 virus might be receding in the U.S., some experts worry that monitoring efforts for bird flu cases are also diminishing. Jennifer Nuzzo, head of the Pandemic Center at Brown University, expresses concern that while recent human cases have been relatively mild, historically, the virus has proven deadly. She pointed out that about half of recognized human cases have resulted in death, which is quite alarming.
Nuzzo, along with Dr. Robert Hopkins from the National Foundation for Infectious Diseases, discussed why human cases of bird flu have not increased since February.
Why haven’t we seen an increase in human bird flu infections since February?
Nuzzo acknowledged the response is uncertain but proposed several potential reasons:
- Migratory bird patterns have changed: Wild birds are key carriers of avian flu. A natural dip in human cases, which typically rise in the fall and early winter months, might be occurring due to seasonal shifts in migration patterns, as suggested by a CDC official during a recent call.
- Less virus circulation: Humans contract bird flu by coming in contact with infected wildlife or livestock. Currently, infections in birds and cattle are still present but less frequent than several months ago, potentially leading to reduced human exposure.
- Decreased testing: There may be fewer human H5N1 tests being conducted, according to Nuzzo, instead of a decline in virus spread. She expressed concern that reduced testing could obscure the real situation, making it difficult to ascertain the genuine threat posed by the virus.
- Lower prevalence in wastewater surveillance: Infected individuals can shed the virus through wastewater. However, while wastes can signal viral presence, they cannot pinpoint the source, and Nuzzo noted that reliance on this method can be limiting.
- Current strain less effective at infecting humans: The CDC sees instances of bird flu reaching several hosts, but human-to-human transmission has not been confirmed. Hopkins noted that the current H5 strain hasn’t yet mutated for easy human transmission.
Experts worry federal government cuts could decrease bird flu monitoring in humans
Nuzzo raised alarms over staffing cuts in the agricultural sector due to the Trump administration’s policies. With more than 15,000 employees having left the USDA, specialized personnel monitoring H5N1 are among those gone. She noted worries exist about states not addressing H5N1 seriously enough, whether through negligence or prioritization issues.
Funding reductions have led to a decrease in communication and coordination among health officials, making it tougher to gauge the overall situation regarding bird flu.
Should the general public be concerned about bird flu right now?
The CDC assesses the risk for the general public as low but acknowledges it’s higher for those in close contact with livestock and wild birds. Nuzzo emphasized that the public at large shouldn’t be anxious right now, but she does worry for agricultural workers who may be exposed to infected animals and might hesitate to seek testing due to fear of job loss or deportation.
Immigrant labor plays a significant role in the dairy industry, and experts have voiced fears that undocumented workers are sidestepping bird flu testing due to immigration fears. Dr. Krutika Kuppalli highlighted the importance of feeling safe for individuals seeking care, as missing testing could hinder early detection, especially among vulnerable groups.
A CDC spokesperson mentioned ongoing outreach efforts to reach farmworkers and any exposed populations.
Will bird flu be the next pandemic?
Nuzzo reminded that pandemics aren’t a new occurrence, with three major influenza pandemics recorded in the 20th century. She is uncertain whether H5N1 will initiate the next pandemic but is confident that another influenza pandemic will happen—tools for addressing it exist, yet their usefulness depends on timely availability.
Regarding the cancellation of the Moderna contract, Nuzzo criticized it as a short-sighted choice that could lead to regrettable consequences down the line.
