In a bid to better understand and control potential H5N1 infections, the U.S. Centers for Disease Control and Prevention (CDC) is urging hospitals to expedite advanced testing for influenza cases, particularly in those hospitalized with flu-like symptoms. This recommendation comes in response to a series of rare, yet concerning, instances of bird flu cases in the U.S., which have occurred without any known animal exposure.
The latest case involves a child in San Francisco who was confirmed to have contracted H5N1 influenza. Another case in Missouri last year also involved a person testing positive for the virus despite no clear exposure to animals. Such cases are puzzling, as they suggest possible human-to-human transmission or a different form of exposure that has yet to be fully understood.
One of the key challenges these cases present is the delay in detecting the specific subtype of the virus. The CDC’s current surveillance system focuses on identifying the virus but does not always immediately pinpoint which strain, such as H1N1, H3N2, or H5N1, is responsible. This gap has made it difficult for public health officials to track how these individuals contracted the virus and whether they may pose a risk to others.
In response, the CDC has recommended that state public health laboratories test all influenza A positive samples for subtyping. This crucial testing allows healthcare providers to determine whether the virus is a seasonal strain or, more rarely, a novel strain like H5N1. Ideally, doctors and hospitals are being asked to perform this testing on hospitalized patients within 24 hours of admission.
Dr. Nirav Shah, Principal Deputy Director of the CDC, emphasized the importance of subtyping in distinguishing between a typical flu virus and one that could be more concerning, such as H5N1. “It’s the subtyping that takes us from knowing that a virus is in the general bucket of ‘influenza A’ to knowing more specifically whether it’s a garden-variety seasonal version or a novel version like H5N1,” he explained.
While there is currently no evidence of widespread human-to-human transmission of H5N1 in the U.S., the virus is still circulating widely in animal populations, and seasonal flu cases are on the rise. Dr. Shah noted that a more rapid and efficient testing system is crucial for detecting potential outbreaks early and preventing further spread. “What we need is to shift to a system that tells us what’s happening in the moment,” he said.
The urgency of this request also reflects the increasing number of hospitalizations due to seasonal flu, with over 100,000 Americans already hospitalized this flu season. The heightened awareness of bird flu cases, combined with the seasonal surge in flu-related hospitalizations, makes it vital to quickly identify and isolate potential H5N1 cases.
In addition to improving surveillance, faster subtyping could help health officials respond more effectively by providing early treatment options. Medications like Tamiflu are most effective when administered early, and timely detection can also help public health officials better understand the trajectory of the virus.
The CDC’s call for faster testing aligns with broader public health goals of strengthening response mechanisms for future influenza outbreaks. As the U.S. government gears up for leadership transitions, significant investments have been made in advancing technologies to combat biothreats, including bird flu. The Department of Health and Human Services recently announced a $211 million investment in RNA-based vaccine platforms, aimed at addressing emerging health threats like H5N1.
With flu season in full swing and public health officials on alert, the acceleration of testing and surveillance for avian influenza represents a crucial step toward safeguarding both individual health and broader public safety. As flu season continues, early detection of novel strains such as H5N1 will be vital in ensuring a swift and effective public health response.
