H5N1 avian flu, historically infecting birds, has recently infected three farm workers. Diagnostic testing may be our best defense.


  1. Recent Spread: H5N1 avian flu has been found in dairy cattle and has infected three U.S. farm workers, indicating increased animal-to-human transmission.
  2. Current Risks: There has been no human-to-human transmission of H5N1 , making a pandemic unlikely for now, though mutation could change this.
  3. Public Health Response: There are established diagnostic tests for avian flu, but these are mainly used at the public health level, and the threat may not be adequately addressed.
By Chris Wolski

Avian flu or H5N1 has infected and/or killed millions of wild, farm, and domesticated birds since it was first isolated in Scotland after an outbreak in chickens in 19591

Recently, H5N1 was discovered in dairy cattle, and, most troubling, in three farm workers in the U.S., who contracted it after being in contact with infected animals, including dairy cows.

While the threat to humans remains low, according to both the U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), it is one we need to take seriously, according to Syra Madad, DHSc, MSc, MCP, CHEP, a fellow at Harvard’s Belfer Center for Science. 

“The animal-to-human risk is increasing, and, as it spreads, more and more we’re playing Russian roulette,” she says. “We often have a very limited window to stop [a disease like H5N1].”

Diagnostic Testing Window 

Does this mean that we’re staring down another worldwide pandemic, similar to SARS-CoV2? According to Madad, not yet for several reasons.

Most important among them is that there has not been any evidence of human-to-human spread. Unlike COVID, H5N1 is not an airborne virus and typically transmitted by coming in contact with dead animals or their waste products. 

The good news is that there is well-established diagnostic testing for avian flu, however they are limited.

“We have tests available, but only at the public health level,” says Madad. These tests are then sent on to the CDC for further verification. 

Signs and Symptoms

There are specific signs in humans for avian flu, including:

  • Cough
  • Headache
  • Shortness of breath and difficulty breathing
  • Sore throat
  • Fever or chills
  • Fatigue
  • Congestion or runny nose
  • Muscle or body aches

Less common symptoms include: diarrhea, nausea, vomiting, and seizures2.

Since all animal-to-human transmission has been linked to persons involved in professions or activities related to animals, it is important for health care providers to do a thorough history, so the correct diagnostic testing is performed.

Another Pandemic on the Way?

While there is no reason to believe that there is another pandemic in our near future, Madad noted that H5N1 has not become a major threat because the virus has remained genetically stable—if it mutates, allowing human-to-human transmission could become more likely.

Less easily transmissible than COVID, H5N1 could pose a more significant threat if it mutates or if there are more animal-to-human infections. According to Madad, there have been about 900 human infections attributed to H5N1 since its discovery with a mortality rate of 50-60%. She added that since 2022, there have been about two dozen sporadic cases, with seven fatalities.

For her part, Madad is cautiously optimistic that we can head off another pandemic. But she also has deep concerns about the way the threat is being addressed.

“I’m dismayed and disappointed at the public health level that they’re not taking advantage of this [diagnostic testing] window,” she says. “I’m not satisfied with the step’s we’ve been taking.”

Chris Wolski is the chief editor of CLP.


  1. 1880-1959 Highlights in the History of Avian Influenza (Bird Flu) Timeline. Centers for Disease Control and Prevention. April 30, 2024.
  2. Avian Influenza and People. 2024.