How Bird Flu Spreads and What You Can Do to Protect Yourself

The H5N1 bird flu isn’t just a poultry issue – it’s a growing global health concern. While human infections remain rare, the virus is closely monitored due to its potential to evolve. This ongoing threat has scientists, farmers, and health officials on high alert. Private Health Management (PHM) researchers and clinicians break down what you need to know about the latest outbreak, its risks, and how to stay safe.

What is bird flu?
Bird flu, or Highly Pathogenic Avian Influenza (HPAI), is a severe, contagious viral disease that affects poultry, wild birds, and sometimes mammals, including humans. Bird flu is caused by a strain of influenza A called H5N1 that was first found to infect humans in 1997. The current outbreak has spread extensively among wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows.¹ Bird flu type A viruses do not normally infect people, but rare cases of human infection have occurred with some viral strains.

As of February 2025, both the U.S. Centers for Disease Control and the World Health Organization still consider the risks posed for humans to be quite low, but they are carefully monitoring the virus, especially in people who work closely with animals. As of February 25, 2025, the U.S. has reported 70 confirmed human cases in humans across 12 states,² mostly among agricultural workers exposed to infected cattle or poultry or had other animal exposures. While past H5N1 outbreaks had a high mortality rate (~50%), there has been only¹ confirmed death in the U.S. The severity of the current strain remains under evaluation, which means this virus could be dangerous if begins to infect more people.²

How does bird flu spread?
Human infections can happen by inhaling the virus that is carried in the air, in droplets or dust, or when a person touches something that has the virus on it and then touches their mouth, eyes or nose. Infection can also be spread by consuming undercooked beef and poultry, and raw milk products that have not been pasteurized. The spread of bird flu viruses from one infected person to a close contact is very rare, and no known person-to-person spread has occurred with the current viruses that are circulating in birds in the U.S. and globally.³

What are the symptoms of bird flu?
Most U.S. bird flu cases have been mild, but some have had severe symptoms. Eye redness is the most common symptom, along with respiratory issues and fever. Symptoms typically appear 2 to 7 days after exposure and last from a few days to under two weeks, though severe cases may persist for weeks.

Mild signs and symptoms	More severe symptoms
• Eye redness and irritation (conjunctivitis) • Mild fever • Cough • Sore throat • Runny or stuffy nose • Muscle or body aches • Headaches • Fatigue	• High fever • Shortness of breath or difficulty breathing • Altered consciousness • Seizures • Pneumonia • Acute kidney failure • Sepsis • Inflammation of the brain (encephalitis)

Bird flu can only be diagnosed through lab testing. Since its symptoms resemble those of flu, COVID-19, and respiratory syncytial virus (RSV), individuals with symptoms should seek medical care for proper diagnosis. Those working with cattle or poultry face a higher risk and should monitor for symptoms for 10 days after exposure to potentially infected animals. While no treatments have been developed specifically for bird flu, it is recommended that patients with confirmed bird flu begin treatment with the antiviral medication Tamiflu® (oseltamivir) as soon as possible.⁴

What are the best ways to avoid infection with bird flu?
The seasonal flu vaccine is not effective for preventing bird flu.⁵ The best way to prevent H5N1 bird flu is to avoid sources of exposure, including direct contact with wild birds and other animals infected with or suspected to be infected with bird flu. For those who must have direct or close contact with these animals, wearing personal protective equipment is recommended. In addition, the below food safety guidelines are recommended:⁵

• Cook poultry and eggs to an internal temperature of 165˚F
• Cook ground beef to an internal temperature of 160°F
• Cook whole cuts of beef to 145°F, then rest for 3 minutes
• Do not touch or consume raw milk or raw milk products (cheese, yogurt, ice cream), especially from animals with confirmed or suspected bird flu infection

Could the bird flu become a pandemic?
The H5N1 outbreak is a potential pandemic threat due to its ability to infect a wide range of hosts, including humans, birds, and other mammals.⁶ While it does not yet spread between people, its widespread transmission in poultry and cattle is concerning.⁷ Public health agencies warn that the virus could evolve or merge with human influenza strains, increasing pandemic risk. Vaccination strategies are being developed, but challenges remain due to the virus’s high pathogenicity.⁸ While the likelihood of an H5N1 pandemic is considered low, its potential impact on human health warrants continuous monitoring and preparedness.^8,9

References

1. CDC. Current Situation: Bird Flu in Dairy Cows. Avian Influenza (Bird Flu) https://www.cdc.gov/bird-flu/situation-summary/mammals.html (2025).
2. CDC. H5 Bird Flu: Current Situation. Avian Influenza (Bird Flu) https://www.cdc.gov/bird-flu/situation-summary/index.html (2025).
3. CDC. Current Situation: Bird Flu in Humans. Avian Influenza (Bird Flu) https://www.cdc.gov/bird-flu/situation-summary/inhumans.html (2025).
4. CDC. Interim Guidance on the Use of Antiviral Medications for Treatment of Human Infections with Novel Influenza A Viruses Associated with Severe Human Disease. Avian Influenza (Bird Flu) https://www.cdc.gov/bird-flu/hcp/novel-av-treatment-guidance/index.html (2024).
5. CDC. Prevention and Antiviral Treatment of Avian Influenza A Viruses in People. Avian Influenza (Bird Flu) https://www.cdc.gov/bird-flu/prevention/index.html (2024).
6. Medina-Armenteros, Y., Cajado-Carvalho, D., das Neves Oliveira, R., Apetito Akamatsu, M. & Lee Ho, P. Recent Occurrence, Diversity, and Candidate Vaccine Virus Selection for Pandemic H5N1: Alert Is in the Air. Vaccines 12, 1044 (2024).
7. Li, K. S. et al. Genesis of a highly pathogenic and potentially pandemic H5N1 influenza virus in eastern Asia. Nature 430, 209–213 (2004).
8. Pappaioanou, M. Highly pathogenic H5N1 avian influenza virus: Cause of the next pandemic? Comparative Immunology, Microbiology and Infectious Diseases 32, 287–300 (2009).
9. Diseases, T. L. I. What is the pandemic potential of avian influenza A(H5N1)? The Lancet Infectious Diseases 24, 437 (2024).