Bird Flu (H5N1): Could It Become The Next Pandemic?

H5N1 strain of bird flu has killed more than 75% of the entire group of baby seals on Heard Island in Australia, as estimated by scienties using data from October, 2025 to January, 2026. The virus has spread across multiple continents since 2020, and now Australia, which remained the only continent to have no cases of H5N1, is in the brink of risk of new outbreak.

Infographic showing key H5N1 bird flu statistics, including over 75% mortality among baby seals on Heard Island, spread across multiple continents since 2020, first detection in dairy cattle in March 2024, 46 human cases across six U.S. states, and 24 additional cases resulting in three hospitalizations and one death.
Figure: H5N1 bird flu continues to evolve and expand its host range. More than 75% of baby seals on Heard Island died during a recent outbreak, while infections in dairy cattle and dozens of human cases in the United States highlight the virus’s ability to cross species barriers and create new public health challenges.

Although human-to-human transmission has not been reported yet, the increasing viral population leads to a greater chance of mutations that may improve adaptation to mammalian hosts. While Ebola and Hantavirus are getting a lot of attention, H5N1 strain of bird flu cannot be undermined.

Mammalian Infections Represent a Critical Warning Sign

Historically, H5N1 was primarily considered as a bird pathogen. However, the increasing number of mammalian infections in seals, sea lions, foxes, mink, cats, and dairy cattle is creating concern in recent years.

In the United States, a study showed that the virus can establish itself in a mammalian population, dairy cattle, while maintaining opportunities for human contact. The Food and Agriculture Organization (FAO), World Health Organization (WHO), and World Organization for Animal Health (WOAH) jointly assessed the situation and noted that continued circulation in birds and mammals increases the likelihood of additional human infections.

Rare Cases of Human Infection but Can Be Severe

According to the CDC, more than 1,000 human H5N1 infections have been reported since 1997, with mortality rate of approximately 48%. H5N1 possesses the ability to cause severe respiratory disease, pneumonia, multi-organ dysfunction and even death, proving it to be a potential pandemic cause.

Infographic showing global human H5N1 bird flu statistics, including over 1,000 reported infections since 1997, approximately 48% mortality rate, 889 laboratory-confirmed cases, 463 deaths, and a 52% case fatality rate across 23 countries from 2003 to April 2024.
Figure: Human H5N1 bird flu infections have remained relatively rare, but reported cases show a high mortality rate. WHO recorded 889 confirmed cases and 463 deaths across 23 countries between 2003 and April 2024, highlighting why H5N1 remains one of the most closely monitored pandemic threats.

From 2003 to April 2024, 889 laboratory confirmed human H5N1 infections were recorded by WHO. The infections spreaded across 23 countries with 463 deaths, corresponding to a case fatality rate (CFR) of approximately 52%.

The Dairy Cattle Outbreak Changed Risk Assessments

H5N1 was detected in dairy cattle for the first time in March, 2024. A report identified 46 human cases across six U.S. states between March and October 2024, almost all liked to infected poultry or dairy cattle. Subsequent surveillance resulted in an additional 24 human cases, with 3 hospitalizations and 1 death.

Overcoming cross species barriers is a remarkable aspect of the current outbreak, which increases chances for mutations to improve mammalian adaptation.

Still Not a High Risk Pandemic Potential

While concerns are justified, there is still not sufficient evidence to suggest that a pandemic is inevitable. According to a review in Frontiers in Microbiology, H5N1 remains poorly adapted for efficient airborne transmission among humans and lacks several characteristics.

However, monitoring the indicators is crucial to prevent further development of H5N1 cases creating global risk. To summarize, these are the warning signs that scientis are currently watching:

  • Increasing numbers of human infections without animal exposure.
  • Evidence of sustained human-to-human transmission.
  • New mutations improving binding to human respiratory tract receptors.
  • Continued expansion in mammalian hosts.
  • Global circulation among multiple continents

Like H5N1, hantaviruses originate in animal hosts and occasionally infect humans. Both diseases highlight the importance of monitoring pathogens circulating in wildlife populations. Read more in our article on Hantavirus: History, Types, and Global Distribution.

References

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