Avian Influenza A Virus

Infected animals act as hosts to influenza viruses by carrying the virus in their intestines and shedding it in bodily fluids, such as saliva, nasal secretions and feces. Other animals become infected when they come in contact with these fluids.

Humans can become infected through contact with infected animals, animal products, or contaminated fluids. Avian flu can spread from birds to people and cause serious illness and even death.

Avian influenza has not mutated to a point where it could easily spread from person-to-person. It's difficult to predict if – or when – that might happen, or if it will result in an influenza pandemic.

People who have gotten sick with avian influenza have been in direct contact with infected animals.

Symptoms of avian influenza in humans range from typical influenza-like symptoms (fever, cough, sore throat, muscle aches) to eye infections, pneumonia, acute respiratory distress, viral pneumonia and other severe and life-threatening complications.

Health care providers will tell patients how to treat their illness, depending on the severity of their symptoms. Treatment may include hospitalization, supportive care and/or the use of antivirals.

Studies have shown that one antiviral drug called Tamiflu (oseltamivir) may possibly protect against the H5N1 strain of influenza.

Yes, it is safe to eat animal products that have been fully cooked. It is not safe to drink unpasteurized (raw) milk. General precautions should always be taken when handling any raw meat, including raw eggs, to avoid possibly spreading germs. These measures include:

• Washing hands and surfaces before and after food preparation.
• Avoiding using the same utensils on raw meat as on other foods, even cooked meat.
• Cooking raw meat thoroughly.

Note: The U.S. bans imports of animal products from areas where birds are infected with the H5N1 virus.

Wastewater monitoring for avian influenza

Wastewater (sewage) can be tested to detect traces of infectious diseases circulating in a community, which has become a valuable new tool for monitoring disease levels in communities. The amount of viral material found in the sewage can help determine how many people might be infected in a community, even if they don’t have symptoms, and can serve as an early warning sign for outbreaks or increasing levels.

The Wisconsin Wastewater Monitoring Program works with wastewater treatment plants across the state to regularly test samples for a variety of diseases including COVID-19 and the flu (influenza). In order to be vigilant for avian influenza, the program recently began testing samples for influenza A(H5), the virus that causes highly pathogenic avian influenza. Samples from selected sites (22 in Wisconsin) are tested twice weekly for this virus. Results are sent to CDC and are displayed on CDC’s National Wastewater Surveillance System Avian Influenza A(H5) dashboard (updated weekly on Fridays). The Wisconsin Wastewater Surveillance Program will make further announcements when plans are in place to display influenza A(H5) data on a state-run dashboard.

Wastewater data alone cannot determine the source of avian influenza A(H5) viruses. They could come from a human or from an animal (like a bird) or an animal product (like milk from an infected cow), and detections of avian influenza  (H5) virus in wastewater do not necessarily indicate human cases. DHS will work closely with the Department Agriculture, Trade, and Consumer Protection (DATCP), local health departments, and utilities after a detection to assist with investigating and responding to possible signs of bird flu in Wisconsin.

To enhance detection of influenza A(H5N1), DHS has designated two streams of surveillance for A(H5N1):

• Before testing decisions can be made, it is critical that clinicians collect information on occupation and animal contacts from all patients presenting with respiratory illness or conjunctivitis.
• Patients should also be asked more specifically whether they have had recent contact with dairy cows, raw milk, poultry, or any sick or dead wild birds or animals through occupational or recreational exposures or if they have traveled internationally.

Once exposure history is determined, testing should occur as follows:

Suspect avian influenza A(H5N1) cases

Call the Bureau of Communicable Diseases (BCD) immediately and request A(H5) testing from the Wisconsin State Laboratory of Hygiene (WSLH).

• Any individuals are considered suspect cases if they are exposed to:
  • Sick animals (sick or dying birds, sick cows, neurologic cats), or
  • Animals with known influenza A(H5N1) infection, or
  • People with known influenza A(H5N1) infection, and who show respiratory symptoms and/or have conjunctivitis.
• Providers should immediately notify BCD of the suspected case and arrange for influenza A(H5) testing at no charge by WSLH.
  • In-house testing, including rapid influenza diagnostic tests to identify influenza A, are discouraged for samples from patients with known contact with affected birds or dairy cattle.
  • Once approved, collect and ship specimens as outlined on WSLH’s H5N1 HPAI webpage.
• Use appropriate infection control measures. If avian influenza A(H5N1) virus infection is suspected, probable, or confirmed in a hospitalized patient, place the patient in an airborne infection isolation room with negative pressure and ensure caregivers implement standard, contact, and airborne precautions with eye protection (goggles or face shield).

Influenza A Surveillance

Any individuals who have animal exposure (backyard flock, outdoor cats, dairy farms) and who show respiratory symptoms and/or have conjunctivitis, but don’t have any reason to suspect influenza  A(H5N1) infection since the animals were not sick, should be tested for influenza.

• Consider local influenza testing, especially polymerase chain reaction (PCR), at your clinical laboratory or a commercial laboratory for patients with respiratory symptoms, but without conjunctivitis, and with exposure to dairy cattle, poultry, or swine.
  • Influenza A-positive specimens from patients with animal exposure should be sent for seasonal influenza subtyping at WSLH.
• For details on seasonal influenza subtyping specimen requirements, visit WSLH’s H5N1 HPAI webpage.
• Enhanced seasonal subtyping of these specimens will allow us to identify influenza A(H5N1) through routine influenza surveillance, as specimens testing positive for influenza A and negative for A(H1) and A(H3) will be further characterized.

In accordance with latest CDC and DHS guidance, please also perform subtyping of influenza A-positive specimens from hospitalized patients, especially those admitted to the intensive care unit (ICU).

• All hospitalized patients with respiratory illness should be tested for influenza using whatever diagnostic testing is most readily available for initial diagnosis.
• For patients who test positive for influenza A with an initial diagnostic test that does not allow for determination of subtype [for example, identify A(H1) and A(H3)], order an influenza A subtyping test within 24 hours of hospital admission.
  • If this is not available at your clinical laboratory or at a commercial laboratory, WSLH will accept all influenza A-positive specimens from those admitted to the ICU and up to three from other hospitalizations per week.
  • Influenza A surveillance specimen requirements can be found on WSLH’s HPAI H5N1 webpage.

Disclaimer: This does not replace or supersede any agreements that your laboratory already has in place with the WSLH. Please continue influenza surveillance testing in accordance with your plans in place with WSLH. 

Additional resources

• Influenza Testing and Variant Influenza A Virus Detection Memo, June 2024
• Conjunctivitis as a Potential Indicator of H5N1, October 2024
• Update: Conjunctivitis as a Potential Indicator of H5N1, November 2024
• Accelerated Subtyping of Influenza A in Hospitalized Patients to Detect Influenza A(H5N1), January 2025

• Influenza A Novel Subtype EpiNet
• CDC Travelers' Health webpage for important information before traveling.
• Wisconsin Department of Agriculture tracks the spread of avian flu in Wisconsin.
• USDA homepage for HPAI in Livestock, including a map of detections, requirements for farms, and guidance for worker safety.
• CDC – avian influenza
  • Center for Infectious Disease Research and Policy (CIDRAP) avian influenza
  • Key facts on bird flu
• U.S. government official website for information on pandemic flu and avian influenza
• Migrant Clinicians Network for information on Avian Flu on Dairy Farms: What Clinicians and Dairy Worker Patients Need to Know
• Department of Agriculture, Trade and Consumer Protection press release
• Resources for workers and employers is available on the DHS Farm Worker Health and Safety webpage
  • What Employers Should Know About Highly Pathogenic Avian Influenza (HPAI), P-03308 Department of Health Services (DHS) fact sheet (multiple languages)
  • What Workers Should Know About Highly Pathogenic Avian Influenza (HPAI), P-03308a DHS fact sheet (multiple languages)