Avian Influenza – Bird Flu

Bird flu infections are unusual in mammals, including humans. Beginning in the spring of 2024, there has been a large outbreak of bird flu among dairy cattle in several states. Four dairy workers have been infected after interacting with sick cows, one in Texas, two in Michigan and one in Colorado. (Last Updated 7/5/2024)

Risk to the public is currently considered low.

What is avian influenza A(H5N1)?

• Avian influenza A (H5N1) is a contagious viral disease that widely affects wild and domestic birds. It is a type of bird flu.
• There are several viral subtypes of bird flu, one of which is A(H5N1).
  • The “A” means “Influenza A”.
  • The H and N refer to different structures on the surface of the virus.
• From 1997 through 2023, about 900 people had been infected with H5N1 globally.
  • Thankfully, not a lot of people are infected each year, and the disease doesn’t seem to infect people easily.
  • But of those that are infected, about 50% die.

Recent History of Bird Flu in the U.S.

• In 2022, the A(H5N1) subtype of bird flu was detected in wild birds in the U.S.
  • One human case was reported in Colorado in 2022.
  • H5N1 began to be detected in various mammal species in 2022.
• In 2022 and 2023, H5N1 caused outbreaks in commercial and backyard poultry flocks around the country.
• In March 2024, H5N1 was detected in goat kids and dairy cows for the first time.
• In early April 2024, a person who worked on a dairy farm in Texas tested positive for H5N1. In May 2024, two dairy workers from Michigan tested positive and in July 2024 a diary worker in Colorado tested positive.
• For the most up to date numbers of impacted dairy herds and affected states, please see CDC’s Current Situation Summary.

Risk to the Public

• The risk H5N1 poses to the general public is considered low.
• However, people who have contact with sick or dead animals (especially birds), or with any lactating dairy cows may be at higher risk than the general public.
  • “Contact” includes interacting with a sick/dead animal or with contaminated materials in the animal’s environment like manure, bedding, and tools that have touched raw milk.
• It is important to note that dairy cows may be infected and able to spread H5N1 but not show symptoms.
  • Testing of dairy cows is not widespread right now so we don’t yet know how often asymptomatic infections happen in dairy cows.
• Consumption of dairy products made with unpasteurized (untreated) milk, also known as raw milk, may be a risk factor. The FDA is still researching this and OSE will update this page as we learn more.
  • Consuming foods made with raw milk is known to increase your risk of gastrointestinal illness from germs like Salmonella and E. coli.
  • Consuming products made with pasteurized dairy is considered safe.

Bird Flu and Nevada

• There have been no detections of H5N1 in either dairy cows or people in Nevada so far, but there have been detections in dairy cows in nearby states.
• To see a summary of the most recent detections of H5N1 in wild birds in Nevada, click here. To see a summary of the most recent detections of H5N1 in domestic poultry in Nevada, click here.
• In late April 2024, the U.S. Department of Agriculture issued a Federal Order to test lactating dairy cows for H5N1 prior to any interstate movement.
  • This requires that any lactating dairy cows coming into Nevada are tested before transport.

Symptoms in Humans, Birds, and Cattle

• H5N1 infections can vary in severity in animals and humans, from asymptomatic infection with no noticeable symptoms, to severe disease and death.
• Symptoms of H5N1 infections in humans may include:
  • Eye redness (conjunctivitis) – this has been the only reported symptom in two of the three human cases.
  • Fever (temperature of 100^oF [37.8^oC] or greater) or feeling feverish
  • If you develop symptoms in the 10 days after you had contact with an infected or potentially infected animal, contact your healthcare provider and be sure to mention your animal contact.
  • You can read more about common symptoms of H5N1 in dairy cattle and in birds on the American Veterinary Medical Association’s website.
  • Cough
  • Sore Throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue
  • Shortness of breath or difficulty breathing
• Less common symptoms include diarrhea, nausea, vomiting, or seizures

Preventative Measures

• Avoid consuming raw milk or food products made with raw milk.
• Be sure to cook meat to the proper temperature.
  • For beef: 160°F for ground beef and 145°F for steaks and roasts
  • For chicken: 165°F for all cuts
• If you find any dead wild birds, do not handle them. Report dead wild birds to the Nevada Department of Wildlife using this form.
• Report any sick or dead backyard birds to the Nevada Department of Agriculture using this email address: Diseasereporting@agri.nv.gov
  • If you must handle sick or dead backyard birds, make sure to use protective equipment such as disposable gloves, safety goggles, rubber boots, and a mask.
• Thoroughly wash your hands after interacting with animals.
  • Wash hands vigorously for at least 20 seconds with soap and water. Dry your hands with a disposable paper towel.
• Stay informed by periodically checking the OSE website and the additional resources listed below!

Additional Resources

• CDC’s Bird Flu webpage: https://www.cdc.gov/flu/avianflu/index.htm
• FDA’s Bird Flu Updates webpage: https://www.fda.gov/food/alerts-advisories-safety-information/updates-highly-pathogenic-avian-influenza-hpai
• One Health Nevada webpage: https://www.onehealthnevada.com/
• USDA’s Bird Flu Detections webpage: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections