Jeremy Farrar, Chief Scientist of the World Health Organization, described the recent spread of bird flu among cattle in the United States as a “huge concern.” While one person in the U.S. has been reported to be infected with the H5N1 strain of bird flu, the broader spread of the disease could be catastrophic. Historically, one out of every two infected individuals has died, potentially signaling a pandemic more deadly than COVID-19. Since the disease was first discovered nearly three decades ago in China, about 860 people have been infected by birds in 23 countries, including China, Egypt, Vietnam, and Turkey, according to the World Health Organization. Among these, 463 people died from the virus, representing a substantial mortality rate of approximately 52%.
Key Features
The main characteristics and features of the new wave of bird flu spreading in the United States can be observed in a manner that allows us to foresee scenarios of it turning into a global pandemic, as follows:
Concerns Over the Geographic Spread of the Virus in the U.S.:
Currently, the bird flu virus (which traditionally spreads only among birds) has spread to cattle, with one human case reported in the U.S. in 2024. Since late March 2024, the H5N1 virus has been reported in about 200 cattle in 36 dairy herds across Colorado, South Dakota, Kansas, Michigan, North Carolina, Idaho, Texas, Ohio, and New Mexico.
Rapid Spread of the Virus Among Birds and Cattle:
Globally, due to the rapid spread of the virus among poultry, farmers have been culling animals exposed to deadly viruses like bird flu. For instance, in early April 2024, a poultry farm in Texas destroyed 1.5 million chickens to limit the virus’s spread. Conversely, there have been no reports of cattle culling as bird flu is not as deadly in cattle as it is in chickens and turkeys.
Potential for the Virus to Spread Beyond U.S. Borders:
In April 2024, a farm worker in Texas contracted the virus in what is believed to be the first transmission from a mammal (cattle) to a human. The individual only suffered mild conjunctivitis and fully recovered after a week. Despite no confirmed cases of bird flu in cattle outside the U.S., the World Health Organization warned of the risk of international spread through migratory birds.
Ongoing Efforts to Explore Human Transmission Pathways:
U.S. public health officials are monitoring cattle herds to assess the extent and speed of the spread. Initially, they assume that cow milk and dairy products might be the most likely means of transmission. Since April 2024, the FDA tested about 297 dairy products, including milk, cheese, and sour cream, finding traces of the virus in 20% of the initial 96 samples. However, further tests confirmed that pasteurization, a heating process used to eliminate harmful pathogens and bacteria from agricultural products, kills the virus and removes the risk to consumers.
Additionally, experts and public health authorities, including the Centers for Disease Control and Prevention, advise individuals to consume only pasteurized dairy products to avoid bacterial infections such as salmonella and brucellosis. So far, U.S. Department of Agriculture (USDA) tests on beef samples have shown negative results for bird flu, but the FDA continues to advise against consuming raw beef.
Ongoing Threat
Based on the main characteristics outlined, the following determinants indicate the potential for this wave to turn into a new global pandemic:
Nature of the U.S. Government’s Response: The potential for the virus to spread globally depends on the U.S. government’s reaction as the first line of defense. Some experts and public health authorities in the U.S. have been studying bird flu for decades, and the COVID-19 pandemic has led to positive shifts in preparedness for disease outbreaks. In late April 2024, the USDA began requiring all dairy cows transported between states to be tested for bird flu. However, testing within state borders remains voluntary, which may not be sufficient to limit the spread as much as U.S. authorities hope.
Response of Other Countries to the Virus Threat: In late April 2024, Colombia became the first country to restrict trade with the U.S. due to bird flu in cattle, limiting imports of beef and related products from states with infected cattle. Mexico, a major market for U.S. beef and dairy products, has intensified its monitoring of livestock entering the country for any signs of the virus. In May 2024, the Canadian Food Inspection Agency also tightened import controls on U.S. livestock, requiring exporters to provide negative bird flu test results for lactating cattle, along with mandatory retail milk testing for the virus. Expanding these measures globally could restrict the virus’s chances of spreading outside the U.S.
Market Capacity to Provide Protective Materials: Experience from the COVID-19 pandemic has made accessing personal protective equipment such as masks and goggles through commercial markets much easier today than before. Even if supply chains are more extensive now, the U.S. strategic national stockpile will have ample supplies for farmers, healthcare systems, and other affected entities, particularly in rural areas.
Readiness for Vaccine Production: Another key preventive measure to avoid the current wave turning into a widespread pandemic is the capability to produce sufficient vaccines for any H5N1 variant. The U.S. National Vaccine Center stated that the federal government contracts with three manufacturers who can quickly produce bird flu vaccines in required quantities. Each uses one of the three FDA-approved platforms for developing egg-based, cell-based, and hybrid vaccines. This means if one platform fails or a company faces production issues, other options are available.
Conclusion: While the new wave of bird flu spreading to mammals, specifically cattle, has raised concerns about its potential to turn into a global pandemic affecting livestock, poultry, and possibly humans, the characteristics of this wave and the external response suggest that the likelihood of it becoming a global pandemic is low based on current data. With no evidence of human-to-human transmission, the Centers for Disease Control and Prevention (CDC) estimates the risk to humans as low. Therefore, it is not expected that the world will soon need to ramp up vaccine production. However, if necessary, countries and governments are likely better positioned to respond than at the start of the COVID-19 pandemic.
