Bird Flu Update: How Regular Influenza May Help Protect You

As cases of H5N1 bird flu rise across the U.S., some of us may be more immune to the virus than others. Many people may have immune cells called “T cells” primed and ready to fight the “highly pathogenic” virus, according to a new study in the journal mBio. “We expect that a degree of pre-existing immunity is present in the general human population that could blunt the severity of human H5N1 infections,” the researchers wrote in the paper. Highly pathogenic avian influenza A(H5N1) virus, also known as H5N1 bird flu, is a viral infection that has seen a large spike in infections across the U.S., in wild birds, poultry, cattle and humans. Stock image of bird flu (main) and white blood cells (inset). Our immune system may be better prepared for infection from H5N1 bird flu if we have recieved a flu shot or been infected with… Stock image of bird flu (main) and white blood cells (inset). Our immune system may be better prepared for infection from H5N1 bird flu if we have recieved a flu shot or been infected with seasonal influenza. ISTOCK / GETTY IMAGES PLUS H5N1 first gained attention in 1997 during an outbreak in Hong Kong, and has since caused periodic outbreaks across Asia, Africa and the Middle East. There are other forms of highly pathogenic bird flu, including H5N6, H5N8, H7N9 and H7N7, and there are also other forms of the virus considered low pathogenic. “Influenza A viruses cause pandemics that can result in millions of deaths. The highly pathogenic avian influenza virus of the H5N1 subtype is presently among the top viruses of pandemic concern,” the authors wrote in the paper. According to the CDC, 66 people across the U.S. have tested positive for H5N1 since the start of 2024, 37 of whom were in California. The other cases are scattered across Colorado, Iowa, Louisiana, Michigan, Missouri, Oregon, Texas, Washington and Wisconsin. In the paper, the researchers describe how they compared the genetic sequences of H5N1 viruses with that of seasonal flu viruses, and found that there were similarities with certain parts of the seasonal flu genome. This means that people who have been infected with the flu or have had a flu shot in the past may have “cross-reactive” T cells ready to mobilize in the case of a bird flu infection. Immune T cells, or T lymphocytes, are a type of white blood cell that plays a central role in the adaptive immune system, helping to identify and eliminate pathogens. Memory T cells in particular “remember” previous infections, allowing the immune system to respond more rapidly and effectively upon re-exposure to the same pathogen. This is why we are less susceptible to pathogens after we have already been infected, or received a vaccine. “We can predict that—in the majority of cases—our T cells have memory responses and can provide pre-existing immunity to H5N1,” study co-author Alba Grifoni, a Research Assistant Professor at the La Jolla Institute for Immunology, said in a statement. “That’s good news.” These cross-reactive T-cells could help us fight H5N1 in the case of it evolving to spread between humans, the researchers say. “We need to continue to monitor the situation, and if an outbreak were to occur, we’re ready to examine immune responses in more detail,” study co-author Alessandro Sette, a professor at the La Jolla Institute for Immunology, said in the statement. There are currently no known cases of human-to-human transmission, with all cases stemming from exposure to infected animals. On December 18, the CDC announced that the first severe H5N1 case in a human had been detected, which is thought to have been caught after exposure to sick and dead birds in backyard flocks. CDC confirms first severe case of H5N1 Bird Flu in the U.S. While an investigation into the source of the infection is ongoing, it has been determined that the patient had exposure to sick and dead birds in backyard flocks. No person-to-person spread of H5 bird flu has been… pic.twitter.com/0jgHKkjQpx — CDC (@CDCgov) December 18, 2024 “A patient has been hospitalized with a severe case of avian influenza A(H5N1) virus (“H5N1 bird flu”) infection in Louisiana,” the CDC said in a statement at the time. “This is the first case of H5N1 bird flu in the U.S. that has been linked to exposure to a backyard flock.” The majority of human cases resulted from exposure to infected cattle, while many others stemmed from poultry farm exposure. 915 dairy herds across 16 states have tested positive for the virus, while nearly 130 million poultry and over 10,000 wild birds have been detected to be infected with H5N1. Twenty big cats in a Washington zoo have also died as a result of H5N1 infection, and on December 18, California Governor Gavin Newsom declared a state of emergency following the spike in cattle cases across the Golden State. “While the risk to the public remains low, we will continue to take all necessary steps to prevent the spread of this virus,” Newsom said in a statement. Is there a health problem that’s worrying you? Do you have a question about bird flu? Let us know via health@newsweek.com. We can ask experts for advice and your story could be featured in Newsweek. References Sidney, J., Kim, A., De Vries, R. D., Peters, B., Meade, P. S., Krammer, F., Grifoni, A., & Sette, A. (2024). Targets of influenza human T-cell response are mostly conserved in H5N1. mBio. https://doi.org/10.1128/mbio.03479-24