What to know
This guidance outlines CDC’s recommendations for preventing human exposures to highly pathogenic avian influenza (HPAI) A(H5N1) viruses and infection prevention and control measures, including the use of personal protective equipment, testing, antiviral treatment, patient investigations, monitoring of exposed persons, and antiviral chemoprophylaxis of exposed persons.
Summary
The purpose of this guidance is to outline CDC's recommendations for preventing exposures to highly pathogenic avian influenza (HPAI) A(H5N1) viruses, infection prevention and control measures including the use of personal protective equipment, testing, antiviral treatment, patient investigations, monitoring of exposed persons (including persons exposed to sick or dead wild and domesticated animals and livestock with suspected or confirmed infection with highly pathogenic avian influenza (HPAI) A(H5N1) virus), and antiviral chemoprophylaxis of exposed persons. These recommendations are based on available information and will be updated as needed when new information becomes available.
Background
Although human infections with HPAI A(H5N1) virus are rare, having unprotected exposure to any infected animal or to an environment in which infected birds or other infected animals are or have been present increases risk of infection. Therefore, people with work or recreational exposures to H5N1 virus-infected animals are at increased risk of infection and should follow recommended precautions.
The panzootic of HPAI A(H5N1) viruses in wild birds has resulted in outbreaks among commercial poultry and backyard bird flocks and has spread to infect wild terrestrial and marine mammals, as well as domesticated animals. Sporadic human infections with HPAI A(H5N1) virus have been reported in 23 countries since 1997 with a case fatality proportion of >50%, but only a small number of H5N1 cases have been reported in humans since 2022. Most human infections with H5N1 virus have occurred after unprotected exposures to sick or dead infected poultry. Since the spring of 2024, sporadic human infections have been reported in the United States. associated with poultry exposures or with dairy cattle exposures associated with the ongoing multi-state outbreaks of HPAI A(H5N1) virus among dairy cattle and poultry. There is no evidence of sustained human-to-human H5N1 virus transmission in any country, and limited, non-sustained human-to-human H5N1 virus transmission has not been reported worldwide since 2007.
Avian influenza A viruses infect the respiratory and gastrointestinal tracts of birds causing birds to shed the virus in their saliva, mucus, and feces. Influenza A viruses can also infect the respiratory tract of mammals and cause systemic infection in other organ tissues. Human infections with avian influenza A viruses can happen when enough virus gets into a person's eyes, nose, or mouth or is inhaled. People with close or prolonged unprotected contact with infected birds (e.g., sick/dead poultry) or other infected animals (e.g., dairy cows) or their contaminated environments are at greater risk of infection. Illnesses in people from HPAI A(H5N1) virus infections have ranged from mild (e.g., upper respiratory symptoms, conjunctivitis) to severe illness (e.g., pneumonia, multi-organ failure) that can result in death.
Since 2022, many different wild bird species have been reported with HPAI A(H5N1) virus infection, including terrestrial, seabird, shorebird, and migratory species. In the United States, HPAI A(H5N1) virus detections in wild birds have been reported in 50 states or territories, and outbreaks in commercial poultry or backyard bird flocks associated with high mortality have been reported in 48 states since February 2022.
A wide range of terrestrial and marine mammals have been reported with HPAI A(H5N1) virus infection in multiple countries, typically resulting in neurologic signs of disease and death. HPAI A(H5N1) virus infection has been reported in wild mammals such as foxes, bears, seals, and sea lions, and in domesticated animals, including pets such as cats and dogs, farmed mink and foxes, and livestock such as goats and dairy cows. In the United States, HPAI A(H5N1) virus detections in mammals have been reported in more than 20 states including detections in dairy cattle herds in 15 states as of November 2024.
At this time, CDC considers the human health risk to the U.S. public from HPAI A(H5N1) viruses to be low; however, people with close or prolonged, unprotected exposures to infected birds or other animals, or to environments contaminated by infected birds or other animals, are at greater risk of infection. CDC considers HPAI A(H5N1) viruses to have the potential to cause severe disease in infected humans and recommends the following:
Recommendations for the Public
Avoid exposure to sick or dead animals. If you are unable to avoid exposure, avoid unprotected (not using respiratory and eye protection) exposures to sick or dead animals including wild birds, poultry, other domesticated birds, and other wild or domesticated animals, as well as with animal feces, litter, or materials contaminated by birds or other animals with suspected or confirmed HPAI A(H5N1) virus infection.
Personal protective equipment (PPE) should be worn when in direct or close contact (within about six feet) with sick or dead animals including poultry, wild birds, backyard bird flocks, or other animals, animal feces, litter, or materials potentially contaminated with HPAI A(H5N1) viruses. PPE includes properly fitted unvented or indirectly vented safety goggles, disposable gloves, boots or boot covers, a NIOSH-Approved particulate respirator (e.g., N95® filtering facepiece respirator, ideally fit-tested), disposable fluid-resistant coveralls, and disposable head cover or hair cover. Adding a face shield over the top of goggles and a fluid resistant apron can enhance protection. Additional information on PPE recommendations for workers can be found online.
Cook poultry, eggs, and beef to a safe internal temperature to kill bacteria and viruses. Refer to CDC's safer foods table for a complete list of safe internal temperatures. Choosing pasteurized milk and products made with pasteurized milk is the best way to keep you and your family safe. Unpasteurized (raw) milk and products made from raw milk, including soft cheese, ice cream, and yogurt, can be contaminated with germs that can cause serious illness, hospitalization, or death. Pasteurization kills bacteria and viruses, like avian influenza A viruses, in milk.
People exposed to HPAI A(H5N1)-virus infected birds or other animals (including people wearing recommended PPE) should monitor themselves for new respiratory illness symptoms, and/or conjunctivitis (eye redness), beginning after their first exposure and for 10 days after their last exposure. Influenza antiviral post-exposure prophylaxis can be considered to prevent infection, particularly in those who had unprotected exposure to HPAI A(H5N1)-virus infected birds or other animals (more information below). Persons who develop any illness symptoms after exposure to HPAI A(H5N1) virus infected birds or other animals should seek prompt medical evaluation for possible influenza testing and antiviral treatment by their clinician or public health department. Symptomatic persons should isolate away from others, including household members, except for seeking medical evaluation until it is determined that they do not have HPAI A(H5N1) virus infection.
Recommendations for Protecting Poultry and Livestock Owners and Workers
Employers should take steps to reduce workers' exposure to novel influenza A viruses such as HPAI A(H5N1) virus from sick animals or contaminated environments. Workers may be exposed when working with animals confirmed or potentially infected with novel influenza A viruses or working with materials, including raw milk, that are confirmed or potentially contaminated with novel influenza A viruses. Examples of potentially exposed workers include:
- Poultry and dairy and other livestock farmers and workers
- Veterinarians and veterinary staff
- Animal health responders
- Public health responders
- Dairy laboratory workers
- Food processing workers handling raw milk and other confirmed or potentially contaminated materials
- Slaughterhouse workers performing certain tasks on lactating dairy cattle including:
- Unloading or handling live lactating dairy cattle for slaughter, including working in holding pens and tasks involved with ante-mortem inspection
- Post-mortem processes including the post-mortem inspection, handling, and transporting of viscera
- Removing and transporting udders from dairy cattle for further processing or rendering
To protect workers who might be exposed, employers should update or develop a workplace health and safety plan, conduct a site-specific hazard assessment to identify potential exposures based on work tasks and setting, and use the hierarchy of controls to identify controls to reduce or eliminate hazards including exposure to HPAI A(H5N1) viruses.
CDC has identified the types of controls that should be used to reduce exposures based on current understanding of the exposure level associated with different work tasks and settings.
For more information and full recommendations, visit:
Recommendations for Clinicians
Clinicians should consider the possibility of HPAI A(H5N1) virus infection in persons showing signs or symptoms of acute respiratory illness or conjunctivits who have relevant exposure history. More information is available at Brief summary for Clinicians. This includes persons who have had contact with potentially infected sick or dead birds, livestock, or other animals within 10 days before symptom onset (e.g., handling, slaughtering, defeathering, butchering, culling, preparing for consumption or consuming uncooked or undercooked food or related uncooked food products, including unpasteurized (raw) milk or other unpasteurized dairy products), direct contact with water or surfaces contaminated with feces, unpasteurized (raw) milk or unpasteurized dairy products, or parts (carcasses, internal organs, etc.) of potentially infected animals; and persons who have had prolonged exposure to potentially infected birds or other animals in a confined space. Clinicians should contact the state public health department to arrange testing for influenza A(H5N1) virus, collect recommended respiratory specimens (more information below) using PPE, consider starting empiric antiviral treatment (more information below), and encourage the patient to isolate at home away from their household members and not go to work or school until it is determined they do not have avian influenza A virus infection. Testing for other potential causes of acute respiratory illness should also be considered depending upon the local epidemiology of circulating respiratory pathogens, including SARS-CoV-2.
Recommendations for State Health Departments
State health department officials should investigate potential human cases of HPAI A(H5N1) virus infection as described below and should notify CDC within 24 hours of identifying a case under investigation. Rapid detection and characterization of novel influenza A viruses in humans remain critical components of national efforts to prevent further cases, to allow for evaluation of clinical illness associated with them, and to assess the ability of these viruses to spread from human to human. State Health Department officials, including the State Public Health Veterinarian, should collaborate with State Department of Agriculture and State Wildlife officials using a One Health approach when relevant to investigate suspected HPAI A(H5N1) infections in people linked with animals.
Recommendations for Monitoring and Testing
People exposed to HPAI A(H5N1)-infected birds or other animals (including people wearing recommended PPE) should be monitored for signs and symptoms of acute respiratory illness beginning after their first exposure and for 10 days after their last exposure. Patients who meet Epidemiologic criteria AND either Clinical OR Public Health Response criteria below should be tested for HPAI A(H5N1) virus infection by reverse-transcription polymerase chain reaction (RT-PCR) assay using H5-specific primers and probes at your state or local public health department.
Epidemiological Criteria
Persons with recent exposure (within 10 days) to HPAI A(H5N1) virus through one of the following:
- Exposure to HPAI A(H5N1) virus infected birds or other animals defined as follows:
- Close exposure (within six feet) to birds or other animals, with confirmed avian influenza A(H5N1) virus infection. Bird or other animal exposures can include, but are not limited to handling, slaughtering, defeathering, butchering, culling, or preparing birds or other animals for consumption, or consuming uncooked or undercooked food or related uncooked food products, including unpasteurized (raw) milk, OR
- Direct contact with surfaces contaminated with feces, unpasteurized (raw) milk or other unpasteurized dairy products, or bird or animal parts (e.g., carcasses, internal organs) from infected birds or other animals, OR
- Visiting a live bird market with confirmed HPAI a(H5N1) virus infections in birds or associated with a case of human infection with HPAI A(H5N1) virus.
- Close exposure (within six feet) to birds or other animals, with confirmed avian influenza A(H5N1) virus infection. Bird or other animal exposures can include, but are not limited to handling, slaughtering, defeathering, butchering, culling, or preparing birds or other animals for consumption, or consuming uncooked or undercooked food or related uncooked food products, including unpasteurized (raw) milk, OR
- Exposure to an infected person – Close (within six feet) unprotected (without use of respiratory and eye protection) exposure to a person who is a confirmed, probable, or symptomatic suspected case of human infection with HPAI A(H5N1) virus (e.g., in a household or healthcare facility).
- Laboratory exposure (unprotected exposure to HPAI A(H5N1) virus in a laboratory)
Clinical Criteria
Persons with signs and symptoms consistent with acute upper or lower respiratory tract infection, conjunctivitis or complications of acute respiratory illness without an identified cause. In addition, gastrointestinal symptoms such as diarrhea are often reported with HPAI A(H5N1) virus infection. Examples include but are not limited to:
- Mild illness (e.g., cough, sore throat, eye redness or eye discharge such as conjunctivitis, fever or feeling feverish, rhinorrhea, fatigue, myalgia, arthralgia, headache)
- Moderate to severe illness: (e.g., shortness of breath or difficulty breathing, altered mental status, seizures)
- Complications: pneumonia, respiratory failure, acute respiratory distress syndrome, multi-organ failure (respiratory and kidney failure), sepsis, meningoencephalitis
Public Health Response Criteria
Testing of asymptomatic persons for HPAI A(H5N1) virus infection is not routinely recommended. However, for the purpose of public health investigations as part of the response to the ongoing H5N1 situation, in consultation with state and local health departments, when feasible, offer a nasal/ oropharyngeal (OP) (+/- conjunctival) swab specimen test for influenza A(H5) virus using the CDC Influenza A/H5 subtyping kit to asymptomatic workers with high risk of exposure to HPAI A(H5N1) virus [e.g., exposed to animals infected with HPAI A(H5N1) virus who reported not wearing recommended PPE or who experienced a breach in recommended PPE], or asymptomatic close contacts of a confirmed case of HPAI A(H5N1) virus infection. Exposed persons should be actively monitored for signs and symptoms of acute respiratory illness or conjunctivitis for 10 days after the last known exposure to HPAI A(H5N1) virus. Any person who develops signs or symptoms of acute respiratory illness or conjunctivitis after high risk of exposure to HPAI A(H5N1) virus, including persons who previously tested negative for influenza A(H5) virus, persons who previously tested positive for influenza A(H5) virus while asymptomatic, and those receiving oseltamivir post-exposure prophylaxis, should be isolated, and tested for influenza A(H5) virus.
Preferred Clinical Specimens
For persons with suspected HPAI A(H5N1) virus infection, the following specimens should be collected as soon as possible after illness onset or when deemed necessary: a nasopharyngeal swab and a nasal swab combined with an oropharyngeal swab (e.g., two swabs combined into one viral transport media vial). The nasopharyngeal swab and the combined nasal-oropharyngeal swabs should be tested separately. If these specimens cannot be collected, a single nasal or oropharyngeal swab is acceptable. If the person has conjunctivitis (with or without respiratory symptoms), both a conjunctival swab and nasopharyngeal swab and/or nasal swab combined with an oropharyngeal swab should be collected. Patients with severe respiratory disease also should have lower respiratory tract specimens (e.g., an endotracheal aspirate or bronchoalveolar lavage fluid) collected, if possible. For severely ill persons, multiple respiratory tract specimens from different sites should be obtained to increase the potential for HPAI A(H5N1) virus detection.
Recommendations for Infection Prevention and Control
Standard, contact, and airborne precautions are recommended for patients presenting for medical care or evaluation who have illness consistent with influenza and recent exposure to birds or other animals potentially infected with HPAI A(H5N1) virus. For additional guidance on infection prevention and control precautions for patients who might be infected with HPAI A(H5N1) virus, please refer to guidance for infections with novel influenza A viruses associated with severe disease.
Recommendations for Influenza Antiviral Treatment and Chemoprophylaxis
Treating Symptomatic Persons with Dairy Cattle or Other Animal Exposures
Outpatients meeting epidemiologic exposure criteria who develop signs and symptoms compatible with influenza should be referred for prompt medical evaluation, testing, and empiric initiation of antiviral treatment with oseltamivir (twice daily x 5 days) as soon as possible. Clinical benefit is greatest when antiviral treatment is administered early, especially within 48 hours of illness onset.
Hospitalized patients who are confirmed, probable, or suspected cases of human infection with HPAI A(H5N1) virus, regardless of time since illness onset are recommended to initiate antiviral treatment with oral or enterically administered oseltamivir as soon as possible. Antiviral treatment should not be delayed while waiting for laboratory testing results.
Detailed guidance on dosing and treatment duration is available at Interim Guidance of the Use of Antiviral Medications for the Treatment of Human Infection with Novel Influenza A Viruses Associated with Severe Human Disease.
Treating Asymptomatic Persons with Bird or Other Animal Exposures Who Test Positive for Influenza A(H5) Virus
Asymptomatic persons exposed to animals infected with HPAI A(H5N1) virus who reported not wearing recommended PPE or who experienced a PPE breach in recommended PPE and who tested positive for influenza A(H5) virus should be offered oseltamivir treatment (unless already receiving oseltamivir post-exposure prophylaxis). Exposed asymptomatic persons who test positive for influenza A(H5) virus should continue to be actively monitored for signs and symptoms of acute respiratory illness or conjunctivitis for 10 days after the last known exposure to HPAI A(H5N1) virus. Any exposed person who tested positive for A(H5) virus while asymptomatic and who develops signs or symptoms of acute respiratory illness or conjunctivitis while receiving oseltamivir for treatment or post-exposure prophylaxis, should be isolated, and tested again for influenza A(H5) virus.
Chemoprophylaxis of Persons with Exposure to HPAI A(H5N1) Virus:
Antiviral chemoprophylaxis is not routinely recommended for personnel who used proper PPE and experienced no breaches in recommended PPE while handling sick or potentially infected birds or other animals or decontaminating infected environments (including animal disposal).
Chemoprophylaxis with influenza antiviral medications can be considered for any person meeting epidemiologic exposure criteria. Decisions to initiate post-exposure antiviral chemoprophylaxis should be based on clinical judgment, with consideration given to the type of exposure, duration of exposure, time since exposure, and known infection status of the birds or animals the person was exposed to. Antiviral chemoprophylaxis is not an alternative for appropriate PPE and engineering and administrative controls, and receipt of PEP should not be contingent upon acceptance of and participation in testing. Offer oral oseltamivir for post-exposure prophylaxis (PEP) and influenza A(H5) testing to exposed asymptomatic workers under the following work tasks or settings with high risk of exposure to HPAI A(H5N1) virus:
*Oseltamivir PEP [twice daily x 5 days (treatment dosing)] can be given to members of poultry culling teams after high risk of exposure (e.g., direct or close unprotected exposure to sick/dead poultry) and to dairy farm workers after high risk of exposure (e.g., unprotected splash in the face with raw cow milk). An unprotected exposure could include breaches in or failures of recommended PPE.
*Longer duration of oseltamivir PEP (e.g., twice daily for 10 days) can be given for ongoing high risk of exposure (e.g., inadequate PPE) to infected animals.
Antiviral chemoprophylaxis is not routinely recommended for personnel who used proper PPE and experienced no breaches while handling sick or potentially infected birds or other animals or decontaminating infected environments (including animal disposal).
If antiviral chemoprophylaxis is initiated, oseltamivir treatment dosing (one dose twice daily) is recommended instead of the antiviral chemoprophylaxis regimen for seasonal influenza. Specific dosage recommendations for treatment by age group is available at Influenza Antiviral Medications: Summary for Clinicians. Physicians should consult the manufacturer's package insert for dosing, limitations of populations studied, contraindications, and adverse effects. If exposure was time-limited and not ongoing, five days of medication (one dose twice daily) from the last known exposure is recommended.
Monitoring and Antiviral Chemoprophylaxis of Close Contacts of Persons with HPAI A(H5N1) virus infection: Recommendations for monitoring and chemoprophylaxis of close contacts of infected persons are different than those that apply to persons who meet bird or other animal exposure criteria. Post-exposure prophylaxis of close contacts of a person with HPAI A(H5N1) virus infection is recommended with oseltamivir twice daily (treatment dosing) instead of the once daily pre-exposure prophylaxis dosing. Detailed guidance is available at Interim Guidance on Follow-up of Close Contacts of Persons Infected with Novel Influenza A Viruses and Use of Antiviral Medications for Chemoprophylaxis.
Vaccination
No human vaccines for prevention of HPAI A(H5N1) virus infection are currently available in the United States. Seasonal influenza vaccines do not provide protection against human infection with HPAI A(H5N1) viruses.
Attribution Statement
N95 and NIOSH Approved are certification marks of the U.S. Department of Health and Human Services (HHS) registered in the United States and several international jurisdictions.
Appendix: Interim Risk Categories by Exposure Table
Categories of individual risk for influenza A(H5N1) virus infection by setting and exposure, including exposure to infected poultry or dairy cows, contaminated animal products, and other suspected infected peri-domestic animals.
Last updated: November 7, 2024
This table [A] provides a framework for epidemiologic assessment of individual risk for highly pathogenic avian influenza (HPAI) A(H5N1) virus infection amidst the ongoing U.S. outbreak of HPAI A(H5N1) viruses in poultry and dairy cows. CDC considers the current risk to the U.S. public from HPAI A(H5N1) viruses to be low; however, persons with exposure to infected animals, or contaminated materials, including raw cow’s milk, are at higher risk for HPAI A(H5N1) virus infection and should take recommended precautions, including using recommended personal protective equipment. This table is intended for use by public health practitioners to help determine how best to prioritize monitoring and investigation efforts among higher risk persons when resources are limited. In summary, among groups exposed to HPAI A(H5N1) viruses, the highest risk for HPAI A(H5N1) virus infection is from close, direct, unprotected contact with animals with confirmed or suspected HPAI A(H5N1) virus infection or their environments and exposure to contaminated raw cow’s milk from infected cows or other products made from contaminated raw cow’s milk.
While data are still being gathered on the current outbreak, current risk assessments are based on expert opinion and supported by historical case examples from the literature. As additional data are gathered from the response, these assessments will be refined, and the risk category associated with some exposures may change.
Setting | Examples of behaviors/activities | Anticipated risk of HPAI A(H5N1) virus exposure relative to the groups listed | Human A(H5) case data supporting risk assessments |
---|---|---|---|
Working [B] on farms with poultry or cows with confirmed HPAI A(H5N1) virus infection or sick poultry or cows exposed to those with confirmed HPAI A(H5N1) virus infection; known close animal contact | Working with poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection in any capacity without appropriate personal protective equipment (PPE)
Providing veterinary care for poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection (including veterinarians, veterinarian staff, farm owners or workers, animal health responders)
Having experienced a breach in PPE, wearing inadequate PPE, or removing PPE incorrectly while handling or working with poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection or their environments Working in environments with poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection
Working with calves (feeding non-heat-treated colostrum, bottle feeding raw milk, watering or medicating calves, cleaning calf pens) Working in maternity pens (calving, providing post-partum care, handling aborted fetuses) Handling other sick or dead animals (e.g., cats, wild birds, poultry) on premises with confirmed HPAI A(H5N1) virus infection in dairy cattle or poultry without appropriate PPE
Non-workers living on dairy or poultry farm premises |
HIGH RISK OF EXPOSURE | Examples of direct/close contact with sick/dead animals with confirmed or suspected HPAI A(H5N1) virus infection.
NEJM Review: Update on HPAI A(H5N1) virus infection in humans [8]: Direct avian-to-human HPAI A(H5N1) virus transmission is the predominant means of human infection, although the exact mode and sites of HPAI A (H5N1) virus acquisition in the respiratory tract are incompletely understood. Handling of sick or dead poultry during the week before the onset of illness is the most common risk factor. Most patients have acquired HPAI A(H5N1) virus infection from poultry raised inside or outside their houses. Slaughtering, defeathering, or preparing sick poultry for cooking; and playing with or holding diseased or dead poultry have all been implicated as potential risk factors. |
Drinking, consuming or exposure to contaminated raw cow’s milk from cows with confirmed or suspected HPAI A(H5N1) virus infection or other products made from contaminated raw cow’s milk | In settings where raw milk is obtained from cows with confirmed HPAI A(H5N1) virus infection or sick cows exposed to those with confirmed HPAI A(H5N1) virus infection
Handling raw milk without appropriate PPE or biosecurity measures
|
Currently, level of risk to humans is unknown but high level of concern based on available animal data | Researchers orally inoculated mice with HPAI A(H5N1) positive milk and found that animals showed signs of illness starting on Day 1. High virus titers were detected in respiratory organs, with medium titers in other organs suggesting systemic infection. Heat inactivation reduced H5 virus titers [9].
On dairy farms in Texas, deaths occurred in domestic cats fed raw colostrum and milk from cows with confirmed HPAI A(H5N1) virus infection. Clinical signs in sick cats included depressed mental status, ataxia, blindness and ocular and nasal discharge [10]. |
Slaughterhouse exposures to cows with confirmed or suspected HPAI A(H5N1) virus infection; known close animal contact | Working in slaughterhouses directly with cows with confirmed or suspected HPAI A(H5N1) virus infection without appropriate PPE
|
HIGH RISK OF EXPOSURE | |
Close or prolonged contact with wild birds with confirmed HPAI A(H5N1) virus infection or their contaminated environments; known close bird contact | Risk would depend on extent of exposure to infected case as well as use of appropriate PPE
Examples of activities:
|
HIGH RISK OF EXPOSURE | Close contact with and defeathering of wild swans was implicated as the source of exposure for two clusters of HPAI A(H5N1) in Azerbaijan [11] |
Occupational exposure to poultry or other animals with confirmed or suspected HPAI A(H5N1) virus infection; known close animal contact | Working at a live bird market (e.g., handling poultry, feeding poultry, cleaning pens, slaughtering/evisceration, carcass and waste disposal) | HIGH RISK OF EXPOSURE | HPAI A(H5N1) in live poultry markets [12, 13, 14]
Environmental evidence of exposure risk from slaughtering sites and other live bird market worker areas in Indonesia [15] |
Household members of a person with confirmed, probable, or suspected HPAI A(H5N1) virus infection; known close human contact | Prolonged unprotected contact with a household member with confirmed or suspected HPAI A(H5N1) virus infection | MEDIUM TO HIGH RISK OF EXPOSURE |
Generally, spread of avian influenza from one infected person to a close contact has occurred only rarely |
Working* on a farm with poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection or sick poultry or cows exposed to those with confirmed A(H5N1) virus infection; no close animal contact | Working on a farm with poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection but with no known direct contact
|
MEDIUM TO HIGH RISK OF EXPOSURE | Few HPAI A(H5N1) cases globally fall into a category of “no known poultry exposure” following investigation of exposures and epidemiologic links. |
Non-farm occupational exposures to poultry or cows with suspected HPAI A(H5N1) virus infection or contaminated animal products (including raw milk); exposure unclear | These types of exposures could occur when a worker comes into contact with a bird or cow (or raw milk) that does not have a confirmed HPAI A(H5N1) virus infection, but comes from a farm that has other poultry or cows or animals with confirmed HPAI A(H5N1) virus infection (or other contaminated raw milk)
|
MEDIUM RISK OF EXPOSURE | |
Time-limited visit to live bird market that has poultry or other animals with confirmed or suspected HPAI A(H5N1) virus infection; known close animal contact | Visiting a live bird market (retail poultry stalls or markets selling live poultry) | MEDIUM RISK OF EXPOSURE | HPAI A(H5N1) in live poultry markets [12, 13, 14] |
Non-farm recreational exposures to poultry or cows with confirmed or suspected HPAI A(H5N1) virus infection or contaminated animal products (including raw milk); known close animal contact |
Agritourism (activities carried out on a farm or ranch that allow members of the general public to visit for recreational, entertainment, or educational purposes, including farming, milking cows, ranching, and harvesting, among other activities. |
LOW TO MEDIUM RISK OF EXPOSURE | Variant influenza A virus infections (non-avian) acquired after exposure to pigs at fairs in the United States [20]
Environmental sample evidence of transmission from backyard chicken feces in China [21] Case in the UK in 2022 associated with captive duck flock [22] |
Time-limited visit to farm with cows with confirmed HPAI A(H5N1) virus infection or sick cows exposed to those with confirmed HPAI A(H5N1) virus infection; no close animal contact | Visitors to farm
|
LOW TO MEDIUM RISK OF EXPOSURE | |
Health care workers exposed to person with confirmed or suspected HPAI A(H5N1) virus infection; known close human contact | Risk would depend on extent of exposure to infected case, including amount of time that a healthcare worker is in close proximity to the infected case and types of interactions (e.g., performing aerosol-generating procedures) as well as use of appropriate PPE | LOW TO MEDIUM RISK OF EXPOSURE | Serologic evidence of patient-to-health care worker transmission in Hong Kong in 1997 [23]
One case of severe illness was reported in a nurse exposed to an infected patient in Vietnam [24] |
Working on farms without poultry or cows with confirmed or suspected A(H5N1) virus infection or sick poultry or cows exposed to those with confirmed HPAI A(H5N1) virus infection; no known exposure | Workers or visitors to farm could be at increased risk if cows or other animals appear healthy but have asymptomatic or pre-symptomatic HPAI A(H5N1) infection.
Examples of activities that would typically only occur on farms without active outbreaks of HPAI A(H5N1) virus infection include:
|
LOW RISK OF EXPOSURE | |
Consuming potentially raw or undercooked poultry products or eggs from poultry with confirmed HPAI A(H5N1) virus infection | In settings where meat and eggs are obtained from poultry with confirmed HPAI A(H5N1) virus infection or sick poultry exposed to those with confirmed HPAI A(H5N1) virus infection
|
LOW RISK OF EXPOSURE | Consuming raw duck blood and organ products was implicated a potential source of exposure in two cases in Vietnam [25]
While HPAI A(H5N1) virus has been isolated from poultry muscle and the interior of eggs, a USDA assessment determined that the risk of infection from consumption is low [26] |
Household members of a person with occupational exposure to poultry or cows or other animals with confirmed or suspected HPAI A(H5N1) virus infection; no known close animal contact | Household exposure via indirect transfer of virus from fomites (e.g., clothing, footwear) obtained from occupational exposure to potentially infected poultry or cows or other animals | LOW RISK OF EXPOSURE | Direct avian-to-human HPAI A(H5N1) virus transmission is the predominant means of human infection. Epidemiological links between affected premises are indirect from shared people, vehicles, and equipment [27] |
A These risk assessments are based on historical data and limited data from the current outbreak; information in the table will be updated as additional data become available.
B Types of workers may include those who work only one farm as well as those who work or travel between multiple farms: farmers, farm workers, deadstock haulers, milk haulers, other contract haulers, feed deliverers, hoof trimmers, transport vehicles, veterinarians and veterinary staff, nutritionists, feed consultants, animal health responders, public health responders.
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