The article talks about a new bird flu called H5N9 that has been detected in poultry in California. It is different from another bird flu called H5N1 that has been spreading. H5N9 is a new strain that is called highly pathogenic because it can be deadly to poultry. The article explains how the virus emerged and why it is concerning. Experts are worried that the virus could mutate and spread easily among humans, causing a pandemic. The article also explains how bird flu viruses are named based on two key proteins on their surface. H5N9 is different from H5N1 in several ways and it is not yet known if it could pose a risk to humans. The article ends by saying that as of now, there is no evidence of H5 bird flu spreading from one human to another in the U.S. Experts are monitoring the situation closely. It is important to watch for any cases in humans and take precautions. Remember, it's always best to stay safe and listen to advice from experts.