
4/20/2025
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Influenza virus is a negative-sense single-stranded RNA virus in the Orthomyxoviridae family. Influenza viruses cause a respiratory illnes also known as “flu”.
Influenza viruses have an outer lipid envelop with spikes composed of glycoproteins termed Hemagglutinin (HA) and Neuraminidase (NA). Influenza virus serotypes are determined by the different types of HA and NA. Sialic Acid is the receptor in the epithelial host cells.
General reference for Avian Influenza, including how transmitted, risk to the public, outlook and references to CDC, USDA, flyer for posting, etc.
Overview site that includes current situation, background, prevention, links to other resources for prevention and monitoring, communication, information for other groups
Fact sheets are available for A(H3N8), A(H7N9), A(H5N1)
Refresh your understanding of avian influenza and its epidemiology in the United States. Review how to recognize, diagnose, and prevent the disease in various animal species. Find out how to report sick birds and other animals.
Outside the United States, more than 950 cases of H5N1 bird flu have been reported to the World Health Organization; about half of those have resulted in death.
This notice temporarily exempts H5 avian influenza viruses from the requirements of the regulations listed in 9 C.F.R. Part 121 for a period of three years; this exemption is consistent with protecting animal health and animal products while allowing more laboratories to conduct research and develop solutions to address the disease. This exemption replaces all previously issued and currently effective exemptions related to H5 avian influenza viruses.
Haney, J., Vijayakrishnan, S., Streetley, J. et al.
The observations define a previously unknown interaction between respiratory viruses that might affect virus pathogenesis by expanding virus tropism and enabling immune evasion.
Leonard J, Harker EJ, Szablewski CM, et al.
These findings suggest the possible benefit of systematic surveillance for rapid identification of HPAI A(H5) virus in dairy cattle, milk, and humans who are exposed to cattle to ensure appropriate hazard assessments.
In this week’s update, CDC shares information about ongoing serology studies in Colorado and Michigan, genetic characterization of viruses from recent human cases in Colorado poultry workers, and how CDC’s National Syndromic Surveillance Program is supporting this response.
CDC provides an update on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or “H5N1 bird flu,” in dairy cows and other animals in the United States.
CDC provides an update on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or “H5N1 bird flu,” in dairy cows and other animals in the United States.
CDC provides an update on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or “H5N1 bird flu,” in dairy cows and other animals in the United States.
This report provides an update to the April 26, 2024, report to include three additional sporadic human cases (1 in Australia and 2 in the United States) and recent activity in wild birds, poultry, and other animals, including the multi-state outbreak in U.S. dairy cattle, and updated information on monitoring for human infections with highly pathogenic avian influenza A(H5N1) virus infections in the United States.
APHIS is maintaining resources, including a list of detections in cattle to date as well as biosecurity information for farmers, veterinarians and farmworkers.
Discusses the FDA current position on pasteurization of milk and the liklihood of infectious virus being present post-pasteurization.
Covers biosecurity, handling and testing guidance for producers, veterinarians, and state animal health officials.
This Health Advisory also includes a summary of interim CDC recommendations for preventing, monitoring, and conducting public health investigations of potential human infections with HPAI A(H5N1) virus.
Describes the case of a person who had exposure to dairy cattle in Texas presumed to be infected with HPAI A(H5N1) viruses.
Several countries from the southern hemisphere have been reporting an early start of the increase of acute respiratory infection during the recent 2023 season of circulation of respiratory viruses, suggesting a shift of seasonal pattern observed prior to the COVID-19 pandemic.
This is the first human infection caused by influenza A(H1N1)v virus reported in the Netherlands in 2023.
There are four types of Influenza viruses: Influenza A, Influenza B, Influenza C, and Infleunza D.
Clade: Clades and sub-clades can be alternatively called “groups” and “sub-groups,” respectively. An influenza clade or group is a further subdivision of influenza viruses (beyond subtypes or lineages) based on the similarity of their HA gene sequences.
CDC follows an internationally accepted naming convention for influenza viruses.
Bulletin of the World Health Organization, 58 (4): 585-591 (1980)
includes status updates on wild birds, poultry flocks and human infections.
The following test are available for diagnosis of Influenza viruses:
The NVSL provides a wide variety of information and services, centered around diagnosis of domestic and foreign animal diseases, support of disease control and eradication programs, reagents for diagnostic testing, training, and laboratory certification.
Brown JD, Black A, Haman KH, Diel DG, Ramirez VE, Ziejka RS, et al.
We detected antibodies to H5 and N1 subtype influenza A viruses in 4/194 (2%) dogs from Washington, USA, that hunted or engaged in hunt tests and training with wild birds. Historical data provided by dog owners showed seropositive dogs had high levels of exposure to waterfowl.
Federal Order to prevent the spread of highly pathogenic avian influenza (HPAI).
Includes the most recent report for confirmed HPAI Findings in Wild Birds. It also includes resources for emergency response.
Includes the most recent report for confirmed HPAI Findings in Wild Birds. It also includes resources for emergency response.
Rathnasinghe R, Jangra S, Miorin L, et al.
In general, moisture and temperature are the two main determinants of viral persistence. At temperatures of 17 to 25 ºC most AI viruses will not survive longer than a few days, even under moist conditions. In general, higher humidity and cooler temperatures permit virus survival in moist substrates over longer periods of time (DEFRA, 2017)
Covers the use of personal protective equipment, testing, antiviral treatment, patient investigations, monitoring of exposed persons, and antiviral chemoprophylaxis of exposed persons
The impact of pandemic influenza outbreaks on individuals and societies can be reduced by being well prepared. This means having a comprehensive plan, that has been tested and refined through conducting exercises, engaging the whole of society.
National plans should be flexible enough to respond to outbreaks of various intensity. Communication will be one of the most challenging tasks during an outbreak and it should be planned well in advance.
Qualls N, Levitt A, Kanade N, et al.
The Influenza Risk Assessment Tool (IRAT) is an evaluation tool conceived by CDC and further developed with assistance from global animal and human health influenza experts. The IRAT is used to assess the potential pandemic risk posed by influenza A viruses that are not currently circulating in people. Input is provided by U.S. government animal and human health influenza experts.
In April 2024, ten cats died in a rural South Dakota (SD) residence, showing respiratory and neurological symptoms. Necropsy and laboratory testing of two cats confirmed H5N1 clade 2.3.4.4b infection.
The International Reagent Resource (IRR), formerly named Influenza Reagent Resource (IRR), was established by the Centers for Disease Control and Prevention (CDC)
NIAID is conducting and supporting research to find new and improved ways to diagnose, treat and prevent influenza infection.
Summary of status of development and availability of avian influenza A(H7N9) candidate vaccine viruses and potency testing reagents
Naraharisetti R, Weinberg M, Stoddard B, et al.
HPAI A(H5N1) virus was detected in two indoor domestic cats with respiratory and neurologic illness that lived in homes of dairy workers but had no known direct exposure to HPAI A(H5N1)–affected farms.
Leonard J, Harker EJ, Szablewski CM, et al.
These findings suggest the possible benefit of systematic surveillance for rapid identification of HPAI A(H5) virus in dairy cattle, milk, and humans who are exposed to cattle to ensure appropriate hazard assessments.
This dashboard provides data about COVID-19, flu, RSV and mpox virus levels in wastewater.
Outside the United States, more than 950 cases of H5N1 bird flu have been reported to the World Health Organization; about half of those have resulted in death.
This site includes monitoring of Persons Exposed to Infected Animals
Monitoring wild bird populations for the earliest possible detection of HPAI by conducting morbidity and mortality investigations and submitting specimens for laboratory testing. Ensuring biosecurity and biosafety on the Service-managed lands and waters to limit spread of the virus. At the request of our partners, assisting with the collection of biological samples for testing live and hunter-harvested birds for HPAI.
Monitoring wild bird populations for the earliest possible detection of HPAI by conducting morbidity and mortality investigations and submitting specimens for laboratory testing. Ensuring biosecurity and biosafety on the Service-managed lands and waters to limit spread of the virus. At the request of our partners, assisting with the collection of biological samples for testing live and hunter-harvested birds for HPAI.
Guidance for identifying human infections with animal influenza viruses and inform risk assessments and public health measures.
This surveillance tool is used to identify viruses that may be circulating in swine, and gain knowledge to contribute to improved animal health diagnostics and vaccines.
Includes data from US Clinical Laboratories, Public Health Laboratories, Outpatient Illness Network, and other sources
Delahoy MJ, Mortenson L, Bauman L, et al.
Data collected through global and regional data sharing platforms
Includes the most recent report for confirmed HPAI Findings in Wild Birds. It also includes resources for emergency response.
This surveillance tool is used to identify viruses that may be circulating in swine, and gain knowledge to contribute to improved animal health diagnostics and vaccines.
Commentary on the PNAS paper
Sun et. al, subscription needed
Genetics
Transmission:
Influenza viruses can be transmitted person-to-person through the following routes:
Prevention:
According to CDC, the single best way to prevent seasonal flu is to get vaccinated each year. Other measures to prevent respiratory illnesses include:
Bird flu has been found in domestic and wild cats in several states. At this time it is known that H5N1 can be transmitted to cats and dogs when they eat products from infected poultry or cattle (e.g., unpasteurized milk, uncooked meat, or unpasteurized eggs) that have not undergone a processing step that is capable of inactivating the virus, such as pasteurizing, cooking or canning.
poster (English and Spanish) designed to help farm workers undertand the risks of avian influenza and how to protect themselves and their families
Covers the use of personal protective equipment, testing, antiviral treatment, patient investigations, monitoring of exposed persons, and antiviral chemoprophylaxis of exposed persons
This page provides information about avian influenza for employers and workers.
OSHA QuickCards by Occupation and additional references for Avian Influenza.
The Pan American Health Organization (PAHO), has drafted a strategic and operational plan to support Member States in responding to pandemic influenza, based on WHO’s preparedness plan.
Summary of changes
This updated guidance identifies select occupational groups that may be at increased risk of exposure to novel influenza A viruses. Specific recommendations for these groups may be updated as CDC learns more during this evolving situation. Persons in these occupational groups should consult with their supervisor or their employer’s worker safety team to determine how best to apply these recommendations.
International experts reach consensus on a set of descriptors to describe how pathogens are transmitted through the air and the related modes of transmission.
Halwe NJ, Hamberger L, Sehl-Ewert J, et al.
We show that bat H9N2 has high replication and transmission potential in ferrets, efficiently infects human lung explant cultures, and is able to evade antiviral inhibition by MxA in transgenic B6 mice. Together with its low antigenic similarity to the N2 of seasonal human strains, bat H9N2 fulfils key criteria for pre-pandemic IAVs.
Big outbreak at a Spanish farm reignites fears of an H5N1 influenza pandemic
Qualls N, Levitt A, Kanade N, et al.
DEFRA Outbreak Assessment 11, Ref: VITT/1200 HPAI in the UK and Europe (conclusion chapter, abridged, edited)
I Sanz-Muñoz, et al.
In this prospective observational study, immune protection against H5N1 and H7N9 avian influenza virus (AIV) was almost absent prior to vaccination. However, seasonal influenza vaccines induced a seroprotective response against the H5N1 subtype in nearly 15% of younger individuals.
France began vaccinating ducks against bird flu in October to try and stem the virus that killed millions of birds worldwide, a move that prompted the United States to impose trade restrictions on French poultry imports.
Grohskopf LA, Blanton LH, Ferdinands JM, Chung JR, Broder KR, Talbot HK
Includes recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2023–24 influenza season (children, adults > 65, pregnant women, immune suppressed, etc.).
McLean HQ, Petrie JG, Hanson KE, et al.
The 2022–23 influenza vaccine provides substantial protection against circulating influenza A viruses and remains the best way to protect against influenza. Influenza vaccination is recommended as long as influenza viruses are circulating.
Information on Seasonal Influenza vaccine, and approved vaccines.
General Precautions (English/Español)
Healthcare Workers (English/Español)
Laboratory Workers (English/Español)
Poultry Workers (English/Español)
Animal Handlers (English/Español)
Food Handlers (English/Español)
Iincludes Guidance for Poultry Employees , Animal Handlers other than Poultry Employees, Laboratory Employees, Healthcare Workers Who Treat Patients with Known or Suspected AI, Guidance for Food Handlers, etc.