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Updated H5N1 Bird Flu FAQ for Clinicians

/ 15 July 2025 / 0 Comments


While news coverage of H5N1 avian influenza (“H5N1 bird flu”) has declined and no human cases have been reported for several months, the virus is still circulating among wild birds, in poultry, and in dairy cows in some areas and thus continues to pose a risk to farmworkers, farmworker families, and rural communities. Migrant Clinicians Network seeks to provide clinicians and health advocates with reliable information so they can best serve workers and the communities that are experiencing outbreaks. This FAQ was updated July 5, 2025. Recommendations and information may change; visit the H5 Bird Flu: Current Situation | Bird Flu | CDC page for the most recent updates.
 

 

 

New questions

What is the latest information about human cases of H5N1 bird flu in the US and worldwide? 

H5N1 bird flu has been detected in more than 169 million chickens from poultry flocks in all 50 states and Puerto Rico, and in dairy farms in 17 states since 2024. Despite the ongoing spread, no new human infections have been reported in the US since February 2025 and the US human case count remains at 70 people. However, human cases of H5N1 bird flu have been reported in seven other countries (Bangladesh, Cambodia, China, India, Mexico, United Kingdom, and Vietnam), including eight deaths as of June 30, 2025.

What is the IRAT and what does it tell us about H5N1 right now?

The Influenza Risk Assessment Tool (IRAT) is a CDC evaluation tool to assess the potential pandemic risk of a virus currently circulating in animals, but not humans. It assesses emergence to cause a pandemic, and what the public health impact would be. The IRAT was recently used to assess two clade 2.3.4.4b influenza A (H5N1) viruses that have caused sporadic human infections in the United States. Both viruses were assessed as “moderate risk” for both emergence and potential public health impact, which is similar to previous IRAT assessments of these viruses. This current risk to the public, “is unchanged and remains low,” CDC notes. This assessment is good news, confirming that H5N1 viruses have not significantly changed their pandemic potential. 

How has government response to H5N1 changed under the Trump Administration?

Vaccines for humans: HHS canceled a Moderna contract to advance an mRNA H5N1 vaccine. An early trial of this mRNA vaccine showed that, after two doses, 97.9% of participants showed a 44.5-fold increase in neutralizing antibody titers from baseline, indicating a positive immune response against H5N1. The Osterholm Update (starting at roughly 42:30) explains why an mRNA vaccine is better suited for a national vaccine stockpile to protect health care workers and essential frontline workers like dairy and poultry farmworkers. There continues to be no indication that the United States is stockpiling vaccines or preparing to launch a widespread vaccination program against H5N1. CDC’s approach at present is to prevent human exposure via biosecurity and with PPE and other occupational controls.

Biosecurity and other farm measures: USDA has initiated a $1 billion H5N1 response, including increased biosecurity assessments and audits, cost-sharing of biosecurity efforts, and increased aid to farmers who cull their flocks to control H5N1 spread. USDA’s strategy also includes funds for “new-generation vaccines, therapeutics, and other innovative solutions to minimize depopulation of egg-laying chickens.”

The following questions from previous FAQs were updated and revised in June 2025.

 

The Basics

What is the difference between H5N1, avian flu, bird flu, and HPAI?

The different names – H5 bird flu, H5N1, bird flu, avian flu, Highly Pathogenic Avian Influenza/HPAI – refer to Highly Pathogenic Avian Influenza A(H5N1) viruses that are spread by wild birds worldwide, caused many poultry outbreaks, and has infected many other kinds of animals, including dairy cows in the US. Influenza A viruses are classified into subtypes on the basis of two proteins on the surface of the viruses. H5N1 virus is a subtype of influenza A viruses that typically infect birds and poultry and are referred to as avian influenza A viruses. The disease they cause is referred to as avian flu or bird flu. There are other subtypes of avian influenza A viruses that have caused human infections, but H5N1 viruses are the ones responsible for poultry outbreaks and also infected dairy cows in the United States. Some poultry farmworkers and dairy farmworkers in the US have been infected with influenza A H5N1 viruses. In this FAQ, we are referring to this virus as “H5N1 bird flu.”

What level of concern should I have at this point?

The risk of H5N1 bird flu still remains low for the general population, but the risk for farmworkers on dairies and poultry farms is higher. However, most human H5N1 bird flu cases have been mild. Workers should be protecting themselves at work and using proper PPE. Clinicians serving dairy or poultry workers need to increase their index of suspicion and respond to cases to ensure that H5N1 bird flu does not spread and mutate. Scroll to the bottom of this CDC page to access a table showing risk by exposure. At this time, this work is critical from a public health perspective.

What H5N1 viruses are there?

There are many different H5N1 viruses. Influenza A virus subtypes can be further broken down into different genetic “clades” and “sub-clades.”  The more common H5N1 virus clade is called B3.13, which has been a main virus found in dairy cows and poultry outbreaks. D1.1, which is now the predominant genotype found in migrating wild birds, also has been detected in poultry and dairy cows in the US. D1.1 has been found to have qualities that could potentially lead to it being more likely to mutate, however, it has not yet been found to be more infectious. However, two severe infections and one death in humans were caused by clade D1.1 viruses in the US. D1.3 is another sub-clade, which comes from D1.1. Like D1.1, it has not been found to be more resistant to antivirals or to be more infectious, but it is being monitored.

What is the recent history of H5N1 bird flu?

H5N1 bird flu viruses have been detected in poultry, cows, wild mammals, wild birds, domestic pets, domesticated farm animals including pigs, and have also sporadically infected humans.

One human case of H5N1 bird flu was reported in 2022 in a poultry worker who only reported fatigue in Colorado. In March 2024, H5N1 bird flu began being detected among dairy herds in the US, and, since then, 70 total human cases and one death (an individual with co-morbidities) have been confirmed in 13 US states.  Among those cases, 41 were related to exposure to sick or infected cattle, 24 to infected poultry exposure, two to other animal exposures, and three cases had unknown exposures. Most were farm workers. CDC also reports seven other probable cases in the US. These numbers remained unchanged from March through June 2025.

Other poultry and dairy farmworkers may have been infected with H5N1 bird flu but did not seek treatment or testing, and/or were asymptomatic (did not have symptoms). Symptoms in people have been mostly mild but, in rare cases, severe, and one death has occurred in the US. in a person who was not a farmworker but who was exposed to backyard poultry  Human infections continue to be rare and the overall risk to the public remains low – but those at higher risk are dairy and poultry workers. The degree of risk is dependent on the exposure, including duration and intensity. The CDC’s Risk Categories by Exposure Table is helpful in determining the risk levels by exposure.

Currently there have been no known cases of human-to-human transmission of H5N1 bird flu in the US, but surveillance for human-to-human transmission is ongoing. In the past, there have been several cases of human-to-human transmission with some bird flu viruses outside of the US, usually among close contact among a patient and a caregiver. This form of transmission is not a high risk to humans in the US at this time.

What resources are out there?

MCN’s Avian Flu page includes links to our bilingual resources, archived webinars, blogs, and more.

CDC’s extensive H5N1 bird flu resources including:

Osterholm Update from CIDRAP 42:30 min in Episode 185: Moderna was working on a vaccine and appeared to have a robust response, but the contract was cancelled.

National Center for Farmworker Health’s H5N1 Bird Flu Response

Upper Midwest Agricultural Safety and Health Center’s Highly Pathogenic Avian Influenza A (H5N1), “bird flu” Toolkit

Western Center for Agricultural Health and Safety’s Limiting Farmworker Exposure To Bird Flu

 

 

Community Spread, Public Health Monitoring, and Prevention

Where is it spreading?

As of June 2025, H5N1 bird flu has been detected in cows in 17 states since March 2024. Not every state tests for H5N1 bird flu so there may be more undetected and therefore unreported cases in the country. H5N1 bird flu has caused many infections in wild birds and mammals, and there are additional sporadic outbreaks among poultry farms, backyard flocks, dairy cows, and domesticated mammals such as cats in the US. No person-to-person spread has been detected. CDC’s H5 Bird Flu: Current Situation reports these figures.

Why has H5N1 bird flu spread in recent years? What has changed?

Poultry outbreaks of H5N1 bird flu are not new and are ongoing. Some poultry workers have been infected in the US after working with sick or dead poultry. The ability to spread from mammal to mammal in dairy cows is new in recent years as the virus mutated. In 2024, the virus was first identified among dairy cattle. Farmworkers are contracting H5N1 bird flu from exposure to infected dairy cows. 

The virus may be spreading from the clothing of humans visiting/inspecting different farms, or possibly through air coming from nearby fields where flocks of infected wild birds have been noticed near farms. The USDA’s epidemiologic brief from June 2024 emphasized that:

  • The spread of H5N1 between states is linked to cattle movements (versus independent wild bird introduction) with further local spread between dairy farms in some states.
  • Disease spread between dairy cattle farms is likely due to many factors, including both direct and indirect transmission routes.
  • Biosecurity is key to mitigate the risk of disease spread.

In October 2024, H5N1 was detected in US swine for the first time, which is concerning due to various factors. Infections in pigs can enhance a virus’s likelihood of changing and being more infectious for both other animals and people. However, there is no evidence to date that H5N1 bird flu virus is circulating in pigs. 

How are human cases, particularly the few cases where there is no known exposure to animals, being detected?

Routine virus panels include tests for seasonal influenza A and B, RSV, and SARS-CoV-2. When tests are submitted to labs, influenza A viruses are further tested and analyzed as part of the United States’ ongoing influenza surveillance system. This includes testing for H5N1 bird flu.  Read more about CDC’s H5N1 bird flu surveillance and human monitoring. 

In cases where patients are very sick, the selection is not random; those patients are tested for a wide range of illnesses. All states participate in this surveillance system.

What can health workers do to prepare for future outbreaks in farmworker communities?

Community outreach workers and outreach teams can:

  • Prioritize communication and relationships with dairy producers to open lines of dialogue and trust between that industry and local sites of health provision serving the dairy’s workers.
  • Create open lines of communication with the local or state health department that is responsible for helping to contain a potential outbreak.
  • Recognize workers’ anxieties – and address them when you can. 
  • Provide education to workers and the community on what would happen if there’s an outbreak and address concerns over loss of work to get tested.
  • Send strong messages and provide resources about prevention that are relevant for farmworkers (See the following question.)
  • Workers should be encouraged to get the seasonal influenza vaccination, when available.
  • Workers should be trained on and test-fitted with appropriate PPE. Hand hygiene should also be tuaght and practiced. 
  • Acknowledge and address the fear and anxiety that workers may have in thinking about working with authorities or weighing the cost of missing work because of a future outbreak.
  • Expand education efforts on H5N1 bird flu and PPE beyond dairy and poultry workers. Food processors and health care workers, including veterinarians, serving these populations also need education.

How can farmworkers prevent illness from H5N1 bird flu?

Prevention is key! Prevention messages for workers include:

  • Do not drink raw milk! Dairy farmworkers sometimes bring milk home. Raw milk consumption from infected cows may cause illness. 
     
  • Practice excellent hand hygiene: Encourage workers to properly wash hands often, and avoid face touching. 
     
  • Understand how exposure happens: Exposure can come from sick animals or their milk, feces, urine, litter, contaminated materials like bedding and straw, or raw (unpasteurized) milk. Surfaces, and water from waterers, troughs, or ponds, may be contaminated with infected animal waste. 
     
  • Get vaccinated against the seasonal flu, when it’s available: All dairy and poultry workers, and others with a higher exposure potential, are encouraged to get vaccinated against seasonal flu when it becomes available in the fall. This vaccine does not prevent H5N1 bird flu, but is designed to protect against three seasonal flu viruses. Vaccination with seasonal flu vaccine  reduces the potential of the person to be co-infected with H5N1 bird flu and seasonal flu simultaneously. Contracting both flus simultaneously increases the risk of reassortment or mutation. (See “Why should farmworkers get the seasonal flu vaccine?”)
     
  • Use PPE to avoid exposure: Workers should wear properly fitted PPE that is appropriate for the work at hand. Workers should focus on protecting their face, nose, and mouth. Those working in dairy with high exposure levels are recommended to wear PPE. Employers should provide PPE at no cost to the employee. Donning and doffing PPE should occur during work hours. See the CDC page for more on preventing exposure before, during, and after wearing PPE. Here are some resources from CDC, available in English, Spanish, and other languages. CDC videos on this topic in English and Spanish will be released soon. 
     
  • If working on a dairy farm, the patient can look for illness among the animals: Dairy cows appear lethargic, and  experience a reduction in milk production. Provide instructions for how to report dairy cow illness to the local animal and health departments. 
     
  • Understand the symptoms and how to report: If a patient feels sick, provide specific instructions for how to report that illness to a clinic or to the local health department.
     
  • Clinicians are encouraged to recognize the difficulty in following occupational guidelines for farmworkers: Wearing PPE and avoiding exposure in a milking parlor where wet surfaces and milk are ubiquitous are challenging. Acknowledge the difficulties and work with the patient to get the maximum level of protection given their work tasks. Prioritize goggles or face shields, which are more easily used in milk parlors. Emphasize respiratory protection as well as gown, gloves, and boots. Determine if work accommodations can be made to reduce potential exposure. Good communication with and support of dairy farm owners are critical.

 

 

Clinical Care for Suspected H5N1 Bird Flu in Workers

What are the symptoms of H5N1 bird flu?

Symptoms have been mild in most cases and are similar to other viruses and the flu. Symptoms may include: 

  • Eye redness (conjunctivitis or “pink eye”)
  • Cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue
  • Fever
  • Shortness of breath or difficulty breathing
  • Diarrhea, nausea, vomiting, seizures (less common)

Fever is not always present in H5N1 bird flu infection and absence of fever should not reduce the index of suspicion. Occupational or recreational exposure to dairy cows, wild birds, or backyard or industrial poultry is critical to assess. 

What do I need to consider if I have a farmworker patient with compatible symptoms to H5N1 bird flu, beyond the basic CDC recommendations?

We recommend that clinicians serving farmworker, dairy worker, and poultry worker patients increase their index of suspicion among patients with symptoms of acute respiratory illness or conjunctivitis. Read CDC’s Brief Summary for Clinicians for more information. On that CDC page, you can see next steps if a clinician suspects H5N1 bird flu in a patient, which are to contact public health as soon as possible regarding specimen collection and to arrange H5N1 testing, and prescribe antiviral treatment with oseltamivir (generic or brand-name Tamiflu). Antiviral treatment works best when started as soon as possible after symptoms develop. Here, we add some notes for clinicians specifically serving farmworker patients:

  • Take a sensitive detailed history to assess potential occupational and recreational exposures. Before directly asking about potential exposures, take a full patient history to understand the patient’s occupation, lifestyle, and living situation. Consider whether the patient may be fearful of disclosing exposures. Low-wage workers, foreign-born people, those with significant financial burdens, those whose housing is associated with their work, and those who may not have legal authorization to work may be hesitant to expose their workplace or may do anything they can to avoid missing work or jeopardizing their job. 
     
  • Explain the importance of uncovering an outbreak, using an interpreter if necessary. It is important for patients to understand what H5N1 bird flu is, why we are tracking the spread, what the symptoms are, and – most importantly – what the next steps are for the patient and the farm if a patient is positive. If the patient’s second language is English, use an interpreter to ensure complete understanding. 
     
  • Follow CDC recommendations. While not routinely recommended, it is critical for public health that clinicians work with state or local health departments to test those who are at high risk because they have been exposed to animals who tested positive for H5N1, have not been wearing PPE while working with animals, and/or have been exposed to another person who has tested positive for H5N1, whether or not they have symptoms. After exposure, patients should be monitored for 10 days after their last exposure and isolated and tested if they develop symptoms. Local or state health departments are coordinating testing; the process may vary by state. While waiting for test results, clinicians should provide oseltamivir (generic or brand-name Tamiflu) to sick patients AND post-exposure prophylaxis (at treatment dosing: twice daily for 5 days) to asymptomatic workers who experienced high-risk exposure, particularly those with insufficient or compromised PPE. CDC recommendations may change; watch the CDC page on interim recommendations for clinicians for updates.
     
  • Clinicians have a responsibility to public health to report cases. Do everything you can to build rapport and trust with the patient so the patient can feel comfortable. If a patient is fearful of uncovering illness or of testing when sick:
    • Contact community health workers, outreach workers, or others on the care team who may already have a relationship with the patient or the patient’s community and can build trust.
    • Use motivational interviewing techniques.
    • Determine the next steps from the local or state health department and provide as much clarity as possible on what the next steps are.

What should I be looking for when assessing a patient for exposure?

Clinicians should always ask about workplace environmental conditions as part of the history intake, especially if working on or near dairy or poultry farms. Patients may have exposure but not have a job title that indicates exposure – for example, a patient may say that she is an accountant, but not disclose without further questioning that she provides accounting for a local farm and goes to the farm for work.

Patients on farms that haven’t yet tested for H5N1 bird flu may still have the virus present. Infected cows may be lethargic, may have higher rates of mastitis, or may experience a drop in milk production. Other animals – particularly cats and poultry, who have high mortality rates from H5N1 bird flu – are better indicators: 80% of dairy farms have cats present, and 50% of H5N1 bird flu-infected farms with cats observed sick or dead cats. More than 20% of dairy farms have chickens or poultry present.

A dairy farmworker was exposed to H5N1 bird flu. What do I do?

Workers who experienced an exposure or whose PPE has been compromised around a H5N1-positive dairy cow herd can be provided antiviral chemoprophylaxis under certain circumstances. Consult CDC’s Highly Pathogenic Avian Influenza A(H5N1) Virus: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations

How do I get my patient tested for H5N1 bird flu?

If your patient has suspected occupational exposures and/or compatible symptoms, clinicians can request a test. Contact your local health department. The local department can tell you whether tests are being coordinated at the local or state level. 

As we are presently outside of the fall and winter “flu season,” clinicians who order a viral panel should have H5N1 in the differential diagnosis if Influenza A returns positive.

While waiting for test results, clinicians should provide oseltamivir (generic or brand-name Tamiflu) to sick patients.

Why should farmworkers get a seasonal flu vaccine?

In the fall, when the seasonal flu vaccine again becomes available, it is important that it is provided to workers on dairy and poultry farms with a heightened risk of exposure to H5N1 bird flu. 

In 2024, CDC launched a special program to make seasonal flu vaccines available for farmworkers in states experiencing H5N1 bird flu outbreak. The seasonal flu vaccine does not protect farmworkers from H5N1 bird flu, but it: 1) will reduce the number of severe seasonal flu cases; 2) may reduce the number of flu-like viruses in circulation to assist in the identification of H5N1 bird flu; 3) prevents co-infection of flu and H5N1 bird flu, which may be more severe and may influence virus mutations. 

Are children at greater risk?

In 2024, one child in Canada with a confirmed severe case of H5N1 bird flu and required weeks of intensive care unit admission was followed by two mild pediatric H5N1 bird flu cases in the US. Initial investigations could not confirm routes of exposure. Both California cases were detected through influenza testing and surveillance and the children experienced mild symptoms. However, given the evolving situation and limited information, no conclusions can be taken from these very few cases on how the current strain of H5N1 bird flu affects children.  CDC’s risk assessment for all people in the general public not working with potentially infected animals, including children, remains low. 

 

 

Animals and Animal Products

Why do poultry with H5N1 bird flu need to be culled when dairy cows do not?

H5N1 is highly infectious among birds, with a 90-100% mortality rate among poultry. Infected poultry typically die within 48 hours of H5N1 bird flu infection. However, among dairy cows, reportedly between 10 and 15% die from infection. Culling is a longtime globally-used practice to contain bird flu outbreaks. In the US, farmers can get compensation from the USDA to help offset the loss of their flocks. Dairy cows do not get as sick and their milk is pasteurized, which ensures it is safe to drink. The current USDA program only compensates live animals who have been culled and does not compensate ones who have already died. While this rule was initially set to try to encourage farmers to detect H5N1 early, the USDA is looking to change this program due to their inability to pay for all of the culled flocks farmers have. This might encourage farmers to find prevention methods for their flocks. For more information see Osterholm Update | CIDRAP.

Can I contract H5N1 from ingesting dairy products, eggs, or chicken? 

Pasteurized milk in the US is safe to drink. Pasteurization effectively inactivates the H5N1 virus in milk. Raw milk is not safe and exposes consumers to H5N1 or other contaminants. Recent studies suggest raw milk cheese may be unsafe too; see this FDA article for more: Investigation of Avian Influenza A (H5N1) Virus in Dairy Cattle | FDA. Properly cooked poultry and eggs are safe to eat. See this website for more: Questions and Answers Regarding the Safety of Eggs During Highly Pathogenic Avian Influenza Outbreaks | FDA.

Should patients be worried about their pets?

Domestic animals and pets are susceptible to H5N1. Cats have tested positive after eating raw pet food. Clinicians can remind patients not to feed pets raw pet food or milk, to keep them away from live or dead wild birds and bird feces, and to prevent cats from eating or interacting with wild birds, or drinking raw milk, which is how it is suspected cats have contracted H5N1. Pets should be kept away from any pet birds including backyard poultry flocks to minimize potential spreading. H5N1-infected cats have a 70% chance of death. While no cat-to-human infections with H5N1 bird flu have been reported at this time, it is best to take precautions if a cat has H5N1. 

 

 

This resource was supported by an independent medical education grant by the National Center for Farmworker Health.