BANBURY, UNITED KINGDOM: A man in a protective body suit walks past a sign warning of a outbreak of ... [+]
The U.S. Centers for Disease Control and Prevention notified the public in early April that an individual in Texas had tested positive for highly pathogenic avian influenza, or bird flu. This person’s only symptom was conjunctivitis—or redness of the eyes—after being exposed to dairy cattle that were presumed to be infected with HPAI. This was the second documented human case of avian influenza in the United States since 2022 and has escalated concerns about a large outbreak—or potentially a pandemic—in the human population.
What Is Highly Pathogenic Avian Influenza?
Influenza viruses, which cause annual epidemics of mild to severe respiratory illness, are not unique to humans. Certain subtypes of influenza circulate among animals, including birds, swine, horses, dogs and bats. Infection in some animals, such as wild waterfowl, may be asymptomatic (i.e., no disease results from the infection) and these animals are considered a natural reservoir for the virus. However, transmission of the virus to other animals, such as backyard bird flocks or commercial poultry, may have devastating consequences.
Since January of 2022, the largest outbreak of avian influenza in recorded history has occurred worldwide. To date, a subtype of highly pathogenic avian influenza—known as H5N1—has been detected in over 9,000 wild birds and has affected greater than 90 million poultry in the United States. Recently, the virus has been identified in certain mammals, including dairy cattle, prompting concern that it may be adapting for more efficient transmission among mammalian species. Although sequencing studies have not yet demonstrated this to be the case, the recent human case in Texas has some asking, “Could avian influenza result in the next pandemic?”
A highly pathogenic subtype of avian influenza, known as H5N1, has affected greater than 90 million ... [+]
How Is Avian Influenza Different Compared to Covid-19?
In early 2020, a novel virus—now known as SARS-CoV-2—began circulating across the globe. The human population had no prior immunity to this virus, no vaccines or treatments existed, and there was limited understanding of how the virus was transmitted and the mechanisms by which it caused disease. These factors contributed to the Covid-19 pandemic, which resulted in over 700 million cases and 7 million deaths worldwide. Although HPAI has the potential to cause a significant outbreak in the human population, there are several significant differences of HPAI that make a global pandemic on the scale of Covid-19 less likely.
We’ve Known About H5N1 For Nearly Three Decades
The highly pathogenic avian influenza subtype H5N1 was first identified in Southern China in 1996 during an outbreak in domestic waterfowl, and it resulted in more than 850 human infections with a mortality rate greater than 50%. Since then, this influenza virus, as well as other low- and high-pathogenic subtypes, have caused outbreaks among animals, and less frequently, in humans. This has allowed researchers, infectious diseases specialists and public health officials to study these viruses and gain valuable insights into their transmission, pathogenicity and potential treatments.
Some Existing Flu Tests Will Detect Avian Influenza
One of the most significant challenges during the early weeks of the Covid-19 pandemic was we had no way to identify who was infected. This allowed for cases to go undiagnosed and fueled the spread of the virus. In contrast, some tests that we currently use to diagnose human influenza—especially molecular tests (e.g., PCR)—will detect avian influenza strains, including H5N1. However, most are not able to subtype the virus. In other words, existing flu tests can tell us we are infected with an influenza virus, but they’re not able to differentiate a common human subtype, like H3N2, from an avian subtype, like H5N1. Partnerships are currently underway to develop tests that are specific for highly pathogenic avian influenza strains.
We Have A Head Start On Vaccines And Antivirals For Avian Influenza
Since we have known about HPAI for nearly three decades, this has allowed researchers time to investigate and develop tools for prevention and treatment. A candidate vaccine against H5N1 exists, and studies have shown that it should elicit a robust immune response against the currently circulating subtype of avian influenza. The CDC has shared it with vaccine manufacturers, so production and deployment could take place rapidly, if needed. In addition, there are multiple FDA-approved antiviral medications used to treat human influenza, and data suggest these treatments are also effective against HPAI. These existing antivirals would help reduce the incidence of severe HPAI cases as well as death.
What Can You Do To Help Prevent An Outbreak of HPAI In Humans?
Although the current risk of a human outbreak of HPAI is low, there are still several steps you can take. First, avoid contact with animals, especially birds or cattle, that are sick or have died. If you must come into contact with these animals, wear eye protection, an N95 respirator and gloves. And finally, get tested for influenza and notify your local or state public health officials if you develop any symptoms—including a sore throat, cough, fever, body aches or conjunctivitis—after being exposed to an animal that might have HPAI.
