Every year, flu season rolls around, sending millions of Americans to the doctor and even hospitalizing many. This year has been particularly tough—2024-2025 has been labeled a 'high severity' season by the CDC, with hospitalization rates hitting a 15-year high.

But there’s a different type of flu making headlines: bird flu, formally known as avian influenza. As of April 8, 2025, it has infected 70 people in the U.S., resulting in two tragic deaths. Experts remain cautiously optimistic, stating that the current threat to humans is low. However, there are growing concerns about the potential for this strain to mutate and spread among people.

The Evolution of Influenza

Influenza has been a major public health concern for centuries, with its first recorded pandemic dating back to 1518. The World Health Organization estimates that flu viruses infect around a billion people annually, with severe cases leading to 3 to 5 million infections that can be deadly.

Influenza belongs to a family of viruses known as orthomyxoviruses, which includes several strains, labeled A, B, C, and D. Among these, influenza A and B are the most dangerous to humans. While influenza A has historically caused four pandemics, influenza B has never triggered a pandemic.

The infamous H1N1 strain was responsible for the devastating 1918 Spanish flu, and a related strain was behind the swine flu pandemic in 2009, infecting over 60 million people in the U.S.

Why Bird Flu Is a Concern

While both swine and avian influenza are forms of influenza A, each primarily targets different hosts: swine flu typically affects pigs, while bird flu is found mainly in birds. This is where the concern mounts—experts warn that an influenza A virus, like the one causing bird flu, might mutate in a way that could allow it to jump to humans, much like what occurred with swine flu.

How Do Seasonal and Bird Flu Differ?

Unlike seasonal flu strains, which circulate annually and are closely monitored by the CDC, the H5N1 strain that causes bird flu is not included in seasonal vaccines. This strain remains uncommon among people, making widespread vaccination unnecessary—there are currently no approved human vaccines for avian influenza.

The Path to Infection

Typically, H5N1 primarily infects birds, but it has made headlines by infecting humans, predominantly poultry workers in close contact with infected birds. Recent outbreaks, particularly the alarming detection of H5N1 in cattle in early 2024, have raised new fears; now there's confirmed human infection from cattle.

As of March 21, 2025, there have been nearly 1,000 global cases of H5N1, with about half resulting in death. Fortunately, there has been no evidence of human-to-human transmission yet.

What Lies Ahead?

As influenza viruses replicate, there’s a risk of mutation—or reassortment—where different strains exchange genetic material, possibly creating new, dangerous variants. This is a significant concern if H5N1 mutates into a form that can easily infect humans.

The CDC, along with the U.S. Department of Agriculture, is closely monitoring these developments, but potential cuts in resources could impact their ability to track threats effectively.

Continual vigilance is essential as researchers and officials strive to stay ahead of any potential outbreak, ensuring public health measures are robust enough to counter any emerging threats from avian influenza.