Bird flu, or avian influenza, is a virus that typically affects birds but can occasionally infect humans. According to the CDC, human cases are rare but can range from no symptoms to severe illness, including pneumonia and, in some cases, death.
The H5N1 strain, a highly pathogenic form, has been detected in mammals across the U.S., Canada, and beyond. It is now widespread among wild birds and has caused major outbreaks in poultry and dairy cattle, including recent human infections among U.S. dairy workers.
This article explores how H5N1 spreads to humans, who is most at risk, and what symptoms to watch for. We’ll also highlight how healthcare providers play a key role in prevention, early detection, and treatment.
What Is H5N1 Avian Flu?
H5N1 is a highly pathogenic strain of avian influenza A that primarily infects birds but can occasionally spread to mammals and humans. The name refers to two key surface proteins: hemagglutinin (H5) and neuraminidase (N1), which help the virus enter host cells.
In birds, the virus binds to alpha-2,3-linked sialic acid receptors, while in humans, it must adapt to bind alpha-2,6-linked receptors. This structural difference limits human infection, but recent mutations in the virus’s HA protein (notably at positions 190 and 226) may increase its ability to infect people.
Avian influenza transmission: Virus adapts from α-2,3 to α-2,6 sialic acid binding and lower fusion pH to enable human-to-human spread. (Photo taken from ScienceDirect website)
H5N1 is now widespread in wild birds and has caused outbreaks in poultry, dairy cows, wildlife, pets, and humans across North America since 2022, as revealed by Harvard Medical School, including human cases in U.S. dairy workers and a severe case in a Canadian teenager.
Though still rare, these developments highlight growing concerns about its potential to spread more easily among humans.
More importantly, the World Health Organization (WHO) has documented 878 cases of Highly Pathogenic Avian Influenza (HPAI) H5N1 in humans with 458 fatalities from 2003 to April 10, 2025.
Additionally, outbreaks have also been noted in poultry and wild birds in 54 nations between 2021 and 2022.
In 2024, the CDC revealed that 46 human cases in adults with 25 connected to infected cows and 20 to infected poultry.
Additionally, as of February 2025, GBH News revealed that the current outbreak of the bird flu is the highest Massachusetts has ever seen. It is now considered widespread, affecting wild birds, poultry farms, and even the price of eggs at the grocery stores.
The news added that there have been 67 reported human cases in Massachusetts.
Can Bird Flu Spread to Humans?
Yes, but it’s not common. Bird flu does not spread easily from person to person and is not transmitted through properly cooked poultry or eggs. Higher risk is possible from future mutations of the avian flu virus, which is now being closely monitored in reported human infection cases.
However, at this time, the human cases are fewer in number.
How Does H5N1 Spread to Humans?
H5N1 avian influenza primarily affects birds, but it can occasionally infect humans through close contact with infected animals or contaminated environments.
According to the CDC, the most common way the virus spreads to humans is through direct exposure to infected poultry or surfaces contaminated with their secretions.
Humans can become infected when the virus enters the body through the eyes, nose, mouth, or by inhaling virus-laden particles in the air. Human infections have occurred mainly through:
- Touching infected birds, especially during handling, slaughter, or cleanup.
- Inhaling contaminated dust or droplets in areas like farms or live bird markets.
- Contact with contaminated surfaces, then touching your mouth, nose, or eyes.
- Exposure to infected mammals, such as recent cases linked to infected cattle.
- Consuming undercooked poultry or eggs from infected sources
This is especially risky during activities such as:
Backyard poultry flocks pose particular concern due to close and frequent interaction with humans, often without proper protective measures. Although human infections remain rare, when they do occur, they can lead to severe illness or even death.
Who is at Risk?
While H5N1 primarily affects birds, certain people face a higher risk of infection through close contact with infected animals or contaminated environments. According to the CDC and WHO, the most vulnerable groups include:
- Poultry workers and farmers
- People involved in bird culling or outbreak response
- Backyard poultry owners
- Live bird market workers
These individuals are more likely to handle sick birds or contaminated materials. Children, older adults, and people with weakened immune systems may also be more vulnerable to severe illness if exposed.
Although human cases are rare and there is no sustained person-to-person spread, the CDC emphasizes using protective gear, practicing good hygiene, and reporting sick or dead birds to limit risk. Awareness and precaution are key to preventing transmission from birds to humans.
Symptoms to Watch For
According to the CDC, bird flu (H5N1) infections in humans can cause a wide range of symptoms, from none at all to severe illness requiring hospitalization.
Common symptoms include:
- Fever or feeling feverish (not always present)
- Cough or sore throat
- Runny or stuffy nose
- Muscle aches, headaches, or fatigue
- Eye redness (conjunctivitis)
- Shortness of breath or difficulty breathing
In more serious cases, infection can lead to pneumonia and severe respiratory illness.
Less common symptoms may include:
- Nausea, vomiting, or diarrhea
- Seizures
Anyone with recent exposure to birds or poultry who develops these symptoms should seek medical attention promptly. Early diagnosis and treatment are key to improving outcomes.
How to Protect Yourself
Protecting yourself from H5N1 starts with avoiding direct contact with infected birds and their environments. The CDC recommends several key precautions, especially for those who work with or keep poultry:
- Avoid touching sick or dead birds, their droppings, or surfaces contaminated with bird secretions.
- Wear protective gear (gloves, masks, goggles, and coveralls) when handling poultry, especially during outbreaks.
- Wash your hands thoroughly with soap and water after any contact with birds or their surroundings.
- Cook poultry and eggs thoroughly to kill any potential virus.
- Report unusual bird deaths to local health or agricultural authorities.
- Monitor your health if you’ve had exposure to birds, especially if symptoms develop within 10 days.
Even though the risk to the general public is low, these steps are vital to prevent infection and reduce the spread of avian flu.
How Can We Help
As bird flu surveillance expands across the U.S., Massachusetts remains a leader in proactive monitoring.
Robert Goldstein, Commissioner of the Massachusetts Department of Public Health, noted that the state was the first to implement dairy farm testing statewide — a collaborative effort with the Department of Agricultural Resources and the Department of Public Health.
At Zenith Urgent Care in Marlborough, we are here to support those efforts by serving as a local health resource for our community. If you’ve had recent exposure to birds or livestock or are experiencing flu-like symptoms such as fever, cough, or fatigue, our experienced medical team is ready to evaluate and treat you.
We offer timely care, accurate symptom assessment, and guidance based on the latest CDC recommendations.
Stay Safe
Although human cases of bird flu are rare, it’s important to stay cautious, especially if you’ve been in contact with poultry, livestock, or wildlife. At Zenith Urgent Care in Marlborough, we’re here to help you stay protected with fast, reliable care and up-to-date medical guidance based on CDC recommendations.
If you’re feeling unwell, experiencing flu-like symptoms, or have concerns after recent animal exposure, our expert team is ready to assist—no appointment needed. We welcome walk-ins and provide thorough evaluations, symptom relief, and peace of mind. You can book your same-day appointment here.
We also encourage everyone to stay current with their seasonal flu vaccine, which helps reduce the risk of severe illness and complications from overlapping respiratory viruses.
Your health is our priority!
Helpful Resources:
For more information and updates on the Bird Flu Transmission Risks to Humans:
- Centers for Disease Control and Prevention (CDC): CDC
- World Health Organization (WHO): World Health Organization (WHO)
- Massachusetts Department of Public Health: Massachusetts Department of Public Health
