Influenza is a clever virus and one that deserves respect. Current concerns with the H5N1 avian influenza virus strain demonstrate why public health around the world continues to watch and monitor for impact on human health. Although the situation is not one that currently affects us on a day-to-day basis, it is important that we have a basic understanding of why this remains newsworthy.

Spread and evolution of H5N1.

Since its emergence, H5N1 has spread across multiple continents, affecting wild birds, poultry, and mammals. In late 2023, the virus was detected in Antarctica for the first time, raising concerns about its impact on native wildlife. By 2024, H5N1 had been reported in various regions, including Europe, Asia, and the Americas, leading to significant poultry losses and economic challenges.

In the United States, H5N1 has been detected in wild birds, poultry, and mammals across all 50 states. As of early 2025, nearly 70 human cases have been confirmed, primarily among individuals with direct exposure to infected animals. In December 2024, the Centers for Disease Control and Prevention (CDC) confirmed the first severe human case of H5N1 in Louisiana, involving a patient hospitalized with severe illness.

We have seen H5N1 move across nonhuman animal species, to situations where humans have become mildly ill after contact with animals, and now to situations where animal contact has resulted in severe human illness.

Since this particular strain of influenza has been detected in a variety of animals, but rarely in humans, what is the concern? The concern centers around the ability of the H5N1 influenza virus to come into contact with other influenza viruses in an environment that will allow an exchange of genetic material. The result may be a different influenza virus with an ability to transmit to and among humans. This process of the sharing of genetic material is called reassortment.

What is reassortment?

Reassortment occurs when a host (such as a pig, human, or bird) is infected with two different influenza strains at the same time; the viral segments can mix during replication, creating a new hybrid strain. The newly formed virus contains a combination of genetic material from both parental viruses, potentially creating a novel strain with altered properties. One of these properties can be an ability to be transmitted within a new species, such as humans.

What conditions enable reassortment?

Reassortment is more likely to occur when multiple influenza strains are circulating at the same time and a ‘mixing vessel’ species, such as pigs, are infected with both a human strain of influenza (such as H3N2 or H1N1—our current human types of influenza) and H5N1 (current avian influenza strain). This may result in a new strain of influenza that is able to replicate within humans and be transmitted among other humans. So, for H5N1 to reassort into a human-transmissible strain, it would need to co-infect a host along with a human-infecting influenza strain.

Why is reassortment dangerous?

Reassortment can create a strain with a completely new combination of genes, making it hard to predict its effects. In addition, a reassorted H5N1 strain could retain its high fatality rate while becoming as transmissible as seasonal flu. If such a strain gains efficient human-to-human transmission, it could spark a new influenza pandemic. That is certainly not something we want to see.

What does this mean to nurses, right now?

Our patients, families and community members continue to recognize nurses as the most trusted and ethical profession. That means they may rely upon us for timely and accurate information regarding H5N1, so we should be ready to answer questions and help clarify or correct inaccurate information or perceptions.

Here are a few points for us:

  • It is important that we realize that presently H5N1 alone is not easily transmissible among humans, but if it reassorts with a seasonal flu virus, it could evolve into a strain where we lack immunity. Although that is a big IF, it is important that we recognize the importance of public health’s continuous monitoring, biosecurity, and research into flu transmission.
  • It does not mean that we can acquire influenza from our food supply, but illness among animals may impact the food supply. We have seen that influenza in poultry reduces the availability of eggs and poultry meat. Food that is in the grocery has been reviewed by our food safety networks and is safe to eat.
  • We should continue our efforts to reduce influenza among the population, since reduced influenza disease reduces abilities of individuals to be a host where multiple influenza viruses can be present and thereby enable reassortment.
  • Nurses should also be aware that influenza and other respiratory viruses are transmitted through the act of breathing and can be transmitted to us during patient care activities.
  • Use of respiratory protection as a barrier to prevent contact with respiratory secretions should be part of our standard practices. This is included in the CDC-recommended standard precautions. If caring for a patient who is coughing, you should protect yourself from contact with respiratory droplets and secretions.
  • A patient does not need to be in isolation in order for you to wear a mask to protect yourself from respiratory droplets and secretions. Use of such barrier precautions is, again, part of standard precautions. Do not hesitate to protect yourself.
  • Pharmaceutical companies are working to prepare vaccines that could be used in the event H5N1 demonstrates an ability to cause transmissible disease among humans. If that would occur, we would be back into situations where rapid and mass immunization could be needed.
  • Nurses should continue to stay up to date on respiratory viruses, including influenza, so we are aware of current public health concerns. We should consult trusted and credible sources for information so we are able to answer questions our patients, families, and communities may pose to us.
  • Most importantly, we must be devoted to our own safety, as we are one of the most critical resources for our communities. We should be knowledgeable about disease transmission and practice infection prevention and control at every point in our patient care activities. If we have questions, we should consult those with expertise in infection control.
  • Excellent sources for basic infection control practices can be found at the CDC website for Project Firstline.

Ruth Carrico, PhD, FNP-C, CIC, FSHEA, FNAP, FAAN, is an adjunct professor in the Division of Infectious Diseases at the University of Louisville School of Medicine and a board certified family nurse practitioner. She has worked in the field of infection prevention and control for more than 30 years and is also board certified in infection prevention and control. Her research and clinical practice focus on disease prevention in all settings where care is delivered and involves public health and care of vulnerable populations.

The author’s recent posts for this blog included “Norovirus, a Formidable and Underappreciated Hazard: What Nurses Need to Know” and “The Critical Role of Nurses in IV Fluid Conservation.”