Why This Matters
More than two years after H5N1 bird flu was first confirmed in a U.S. dairy herd, the outbreak is still growing. As of July 22, 2026, the USDA's Animal and Plant Health Inspection Service (APHIS) has confirmed over 1,166 infected dairy herds across 19 states, with Idaho now leading the national count at 173 affected herds.
For most Americans, the direct public health risk remains low. But the continued spread raises three ongoing concerns: the safety of raw milk for the small fraction of consumers who seek it out; the cumulative exposure risk for the estimated 700,000 dairy farm workers in the United States; and the background concern voiced consistently by virologists and public health experts: that sustained viral replication in a mammalian population increases the statistical opportunity for mutations that could affect human transmissibility.
What We Know So Far
USDA APHIS reported on July 22 that Idaho confirmed nine new dairy herd infections during the 30 days ending July 22, with the last reported detection in the state occurring July 13. Utah added 13 new cases over the same period, 12 of them on dairies, with the last Utah detection occurring July 17. Texas added two new cases in the same window.
Since the outbreak began in March 2024, Idaho has recorded a cumulative total of 173 infected livestock premises, all but one involving dairy milking cow operations. This is the highest active-state total in the current phase of the outbreak, according to Capital Press.
The FDA has continued to affirm that commercially sold pasteurized milk is safe. Pasteurization destroys H5N1 at standard processing temperatures. Raw (unpasteurized) milk from infected cows, however, can carry active virus. The FDA recommends that dairy processors not use milk from infected cows in raw milk products, and urges consumers to avoid raw milk during the outbreak.
Where the Risk Is Highest
Idaho's dairy corridor, concentrated in its southern counties including Canyon and Twin Falls, has been the most active zone for new herd infections in 2026. The Idaho State Veterinarian Scott Leibsle has noted that the bird flu strain circulating in Idaho dairy herds is spreading primarily among cattle rather than from wild birds, driven by shared equipment and shared personnel working across multiple farms.
Utah's recent activity has included both dairy herds and one commercial layer poultry operation in Cache County, making it one of the few states with concurrent confirmed infections in both livestock categories in 2026.
California, which previously led all states with 773 affected herds, has not identified a new infected livestock herd since November 2025, and released all dairies from quarantine in February 2026. California's experience suggests that aggressive testing, quarantine protocols, and biosecurity upgrades can eventually slow transmission within a state, though the process takes many months and requires sustained coordination between state and federal agencies.
What Doctors and Experts Say
The American Veterinary Medical Association (AVMA) notes that the mortality rate for dairy cows infected with H5N1 appears low. Affected animals typically recover, return to milk production, and do not need to be culled. Clinically ill lactating cows show symptoms including reduced feed consumption, sudden decline in milk production, thick and discolored milk, and fever.
Idaho State Veterinarian Leibsle told Capital Press that warmer, drier summer conditions may help slow the virus's spread in his state. He emphasized that the strain in Idaho dairy herds "is spreading primarily among cattle rather than from wild birds." That distinction that affects the type of biosecurity intervention most likely to be effective.
The CDC's public human health risk assessment for H5N1 in dairy cattle remains low for the general U.S. public. Testing to date has not found changes in the virus that would make it more transmissible to humans, according to USDA APHIS. No person-to-person spread has been detected in any of the human cases identified in the United States since the dairy cattle outbreak began.
What the Evidence Shows and What It Does Not
The dairy cattle H5N1 outbreak has produced a small number of human infections since 2024, all in people with direct exposure to infected animals, primarily dairy farm workers. No community spread of H5N1 from human to human has been detected in connection with the dairy outbreak.
MedicalDaily Evidence Check
- Data source: USDA APHIS confirmed herd detections, July 22, 2026; Capital Press, July 22, 2026
- What it shows: 1,166+ infected dairy herds confirmed since March 2024; Idaho leads with 173 herds; 19 states currently affected
- What it does not prove: That H5N1 poses imminent risk to consumers of pasteurized milk; no evidence of human-to-human transmission
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What readers should know: Pasteurized milk is safe; raw milk from infected herds poses a risk and should be avoided; farm workers with direct cattle exposure should use protective equipment and report any flu-like symptoms promptly
Who Faces the Greatest Risk?
- Dairy farm workers with direct contact with infected or potentially infected cattle
- Consumers who purchase raw (unpasteurized) milk or raw milk cheese in states with active outbreaks
- Veterinary and laboratory personnel handling specimens from infected animals
- Poultry operations located near affected dairy farms, due to documented spillover events
The general public, including everyone who drinks commercially pasteurized milk, does not face an elevated risk from the dairy H5N1 outbreak, according to both the CDC and the FDA.
Symptoms and Warning Signs to Watch For
Farm workers and others with direct contact with potentially infected dairy cattle should watch for:
- Conjunctivitis (eye redness, discharge, or irritation)
- Fever or chills
- Cough, sore throat, or runny nose
- Muscle aches
- Shortness of breath
The CDC recommends that farm workers with these symptoms following cattle exposure contact their local or state health department, report their occupational exposure, and seek prompt medical evaluation. Antiviral treatment with oseltamivir (Tamiflu) is most effective when started early.
What You Can Do Now
- For farm workers: Use personal protective equipment, including gloves, goggles, and a properly fitted N95 respirator, when handling cattle on premises with known or suspected H5N1 infection.
- For dairy producers: Enroll in USDA or state testing programs and follow the APHIS biosecurity guidelines, including restricting cross-farm personnel movement and disinfecting shared equipment between uses.
- For consumers: Purchase only pasteurized dairy products from licensed commercial processors. Avoid raw milk, raw milk cheese, and other unpasteurized dairy products.
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For all:
Do not handle sick or dead wild birds or other animals; report unusual bird or livestock deaths to your state agricultural department.
Cost and Access: What Patients Should Know
The USDA's Emergency Assistance for Livestock, Honeybees, and Farm-raised Fish Program (ELAP) provides financial assistance to eligible dairy producers for milk losses resulting from confirmed H5N1 infection. Producers with positive test results may be eligible for compensation for reduced milk production during the quarantine period.
For farm workers who develop symptoms, standard influenza testing through most health-care providers can detect H5N1. Workers without insurance may access evaluation through federally qualified health centers or state and local health department clinics.
What Happens Next
USDA APHIS updates its confirmed herd count regularly on its HPAI livestock page. Several H5N1 vaccine candidates for dairy cows are currently undergoing USDA-supported field trials, though no vaccine is yet approved for use in cattle.
The ongoing National Milk Testing Strategy (NMTS), which requires raw milk samples from dairy processing facilities nationwide to be submitted for H5N1 testing, continues to serve as the primary early warning system for new herd-level infections. Results from the NMTS are reported to USDA and state veterinary authorities.
MedicalDaily will continue monitoring USDA herd updates and will report on any changes to the human risk assessment or raw milk safety guidance.
The Bottom Line
H5N1 bird flu has now infected more than 1,166 U.S. dairy herds across 19 states, with Idaho currently the most active outbreak state. For the vast majority of Americans, the risk from the dairy cattle outbreak remains low: commercially pasteurized milk is safe, and no human-to-human spread has been detected. The most immediate risk falls on dairy farm workers with direct animal exposure, who should use protective equipment and report any flu-like symptoms to their health-care provider.
