Novel and Variant Influenza (Flu) A Viruses

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How Influenza Viruses Change

Influenza (flu) viruses constantly change. The changes can happen slowly over time or suddenly.   

Slow changes are called antigenic drift. Every flu season, usually from October to May in the United States, different types of influenza A and B viruses are passed from person-to-person, causing illness. The slow and constant changes to the flu virus are the reason people need to get a new flu vaccine each year. More information about seasonal flu and how to prevent it can be found on the VDH Flu Basics webpage. 

Fast, sudden changes to flu viruses are called antigenic shift which only affects influenza A viruses. This occurs when two flu viruses combine to form a virus with a new subtype or a mix of genes (including some from animals). Because people have little or no immunity to the new virus, it can lead to a pandemic. An example of this occurred in the spring of 2009, when a new H1N1 virus with a different combination of genes (from pigs, birds, and humans) emerged in people and quickly spread.  

Novel and Variant Influenza A Viruses 

Novel and variant influenza A viruses are different viruses from current seasonal human influenza A viruses that circulate among people. These viruses are found in animals, including ducks, chickens, pigs (swine), whales, horses, seals, and cats. While it is unusual for people to get influenza infections directly from animals, sporadic human infections and outbreaks caused by influenza A have occurred. Some novel influenza A viruses are believed to pose a greater pandemic threat than others.  

  • Novel influenza viruses can originate in animals where it gains the ability to infect and spread among humans or can be a human flu virus that changes significantly from the current seasonal flu A viruses.   
  • Avian influenza or “bird flu” normally circulates in wild aquatic birds and can infect domestic poultry and other bird and animal species. Avian influenza viruses that have infected people are considered to be novel influenza A viruses. 
  • Variant influenza viruses occur when people are infected with swine flu viruses, such as H1N2v and H1N3v. Swine flu is a respiratory disease of pigs that regularly causes outbreaks of flu in pigs.  

How can a person get infected?

Human infections with influenza A viruses from animals are uncommon, but have occurred sporadically, usually after unprotected exposure to sick or dead infected poultry, swine, or virus-contaminated environments. People with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection. Ongoing spread of novel or variant influenza viruses between humans is not occurring at this time.   

What are the symptoms?

Symptoms in humans from avian influenza can range from no symptoms or mild illness such as eye redness, mild flu-like upper respiratory symptoms (fever, cough, sore throat, runny nose) body aches, and tiredness. Symptoms can also be severe (like pneumonia) requiring hospitalization. Less common symptoms include diarrhea, nausea, vomiting, or seizures. Illness from variant virus infections (from pigs) have been mostly mild with symptoms similar to human seasonal flu.  

What is the treatment? 

Antiviral drugs that are used to treat seasonal flu are used to treat infections. They are most effective when taken within 48 hours of when symptoms start. 

 How can an infection be prevented? 

  • Avoid unprotected contact with sick or dead birds, pigs, cattle, or other animals. Also avoid unprotected contact with raw milk, feces (poop), animal litter, or other materials potentially contaminated by sick birds or animals. Sick or dead wildlife can be reported to the Virginia Department of Wildlife Resources (VDWR) via the Virginia Wildlife Conflict Helpline at 855-571-9003 or by completing the form at VDWR Sick, Injured, Dead Wildlife Reporting System. If you find a dead bird on your property, contact your local health department for their awareness and guidance to protect your health.  
  • Don’t visit swine exhibits if you are exhibiting flu-like symptoms.  
  • Do not eat or drink in areas with pigs. Avoid taking toys, pacifiers, baby bottlers, or similar items into areas with pigs. 
  • Eat food that is fully cooked. Eat meat and poultry that is fully cooked (not pink) and served hot. Eat hard-cooked eggs (not runny). Don’t eat or drink dishes that include blood from any animal.  
  • Do not eat or drink unpasteurized (raw) milk or raw milk products, like unpasteurized cheese. 
  • Call your local health department and follow their guidance and self-monitor for new respiratory illness or conjunctivitis (eye redness, irritation) if you come into contact with birds, cattle, pigs or other animals suspected of infection with influenza viruses through job duties or hobbies. People with exposure to infected birds, livestock, or other animals have a greater risk of influenza virus infection, and would include poultry and dairy farm workers, hunters, backyard or hobbyist flock owners, and fair exhibitors. 
  • Practice good hand washing and cleanliness, especially after contact with animals and surfaces at petting zoos or other farms where animals are able to be touched. Wash your hands often. If soap and water aren’t available, clean your hands with hand sanitizer containing at least 60% alcohol. Don’t touch your eyes, nose, or mouth. If you need to touch your face, make sure your hands are clean. Cover your mouth and nose with a tissue or your sleeve (not your hands) when coughing or sneezing. Clean and disinfect any personal belongings that may have had contact with animals or their environments prior to leaving the farm or exhibit, such as strollers, purses, toys, etc. 

 What to do if you were exposed 

  • See a healthcare provider if you become ill (even if symptoms are mild) after coming into contact with sick birds, poultry, cattle, or other animals and let them know of your recent exposure. Stay away from other people (isolate) and do not go to work or school until you have been evaluated. People who have been exposed to novel or variant virus may be given antiviral medications to prevent infection. This will be decided on a case-by-case basis.  
  • For more prevention information, please see CDC’s webpages on Swine Flu and Bird Flu. 

 For more information: 


2024 H5N1 Influenza A Virus Updates 

About H5N1 

A strain of Highly Pathogenic Avian Influenza (HPAI A)(H5N1) novel influenza A virus emerged  in 2020 and resulted in wild bird infections and poultry outbreaks in many countries, including the United States. This HPAI A(H5N1) virus is circulating in birds and is often referred to as an “avian flu” or “bird flu” virus. This HPAI A(H5N1) virus is also called a highly pathogenic avian influenza (HPAI) virus because it can cause severe disease and death in infected poultry. In the United States, a small number of sporadic HPAI A(H5N1) infections have occurred in people presenting with mild illness and each recovered. No known human-to-human spread has occurred with the HPAI A(H5N1) viruses that are currently circulating in birds in the United States and globally. The current risk of infection to the general public is low.   

Latest Updates 

In Virginia, HPAI A(H5N1) has not been detected in people or dairy cattle.  

On May 22, 2024, CDC confirmed that a second person this year tested positive for HPAI A(H5N1) after exposure to dairy cattle presumed to be infected with HPAI A(H5N1). The person from Michigan was a dairy farm worker and had mild symptoms. This is the second report of the spread of HPAI viruses from cows to people and the third person to test positive for HPAI A(H5N1) virus in the U.S. 

On April 5, 2024, CDC released a health advisory to inform health care providers, state health departments, and the public of a person in Texas recently confirmed to be infected with HPAI A(H5N1) virus in the United States following exposure to presumably infected dairy cattle. 

On April 1, 2024, CDC confirmed, that a person in Texas tested positive for HPAI A(H5N1) after exposure to dairy cattle presumed to be infected with HPAI A(H5N1). The patient had mild symptoms and was treated with an antiviral drug for flu. This the first report of the spread of HPAI viruses from cows to people and the second person to test positive for HPAI A(H5N1) virus in the U.S.  

On March 25, 2024, the first HPAI infections in dairy cows were reported in Texas and Kansas. 

On April 28, 2022,  CDC reported the first infection of HPAI A(H5N1) virus in a person in the U.S. after direct contact with poultry. 

Since January 2022, HPAI A(H5N1) has been circulating in North America in wild birds. Since then, it has spilled over to infect backyard and hobbyist flocks(chickens), cattle, commercial poultry, wild terrestrial, and marine mammals, as well as domesticated animals (dogs, cats).   

What is VDH Doing? 

  • Working closely with the Virginia Department of Agriculture and Consumer Services and the Virginia Department of Wildlife Resources to monitor the current H5N1 bird flu situation in wild birds and poultry, dairy cows, and sporadic infections in other mammals. VDH is the lead state agency for human health. 
  • Monitoring health data and disease trends to rapidly spot indicators of concern.  
  • Monitoring exposed workers if a detection of HPAI A(H5N1) occurs. 
  • Working closely with the Division of Consolidated Laboratory Services to ensure capacity and preparedness for laboratory testing.    
  • Engaging in outreach and education with partner organizations and healthcare providers.  

 General Information on H5N1

 Resources for Agriculture (Farmers, Poultry, and Livestock Owners)  

Resources for Healthcare Professionals 

Clinician Outreach  

 Evaluation Criteria 

Laboratory Testing 

Treatment and Chemoprophlaxis 

Infection Control and Personal Protective Equipment (PPE) 


Page last updated May 28, 2024