California officials have declared a state of emergency over the spread of bird flu, which is tearing through dairy cows in that state and causing sporadic illnesses in people in the U.S. That raises new questions about the outbreak of the virus, also known as Type A H5N1.

At first glance, it looks like an unassuming Iowa farm.

Scientists are trying to determine why bird flu kills some animals quickly but leads to mild illnesses in others.

The bird flu outbreak in U.S. dairy cows is prompting development of new, next-generation mRNA vaccines — akin to the shots deployed during the COVID-19 pandemic.

Doctors have a message for vaccine-weary Americans: Don't skip your flu shot this fall.

Health officials say it’s OK to get your COVID-19 vaccine and flu vaccine at the same time.

Health experts are worried Americans might have vaccination fatigue, but they still want you to get your flu shot.

FILE - In this Jan. 22, 2021, file photo, empty vials of the Pfizer-BioNTech COVID-19 vaccine are seen at a vaccination center at the University of Nevada, Las Vegas, in Las Vegas. The makers of COVID-19 vaccines are figuring out how to tweak their recipes against worrisome virus mutations if and when the shots need an update. The good news: Many of the new COVID-19 vaccines are made with new, flexible technology that’s easy to upgrade. TESTING VACCINES 2.0First-generation COVID-19 vaccines were tested in tens of thousands of people to be sure they work and are safe — research that took many months. After all, flu vaccines protect against three or four different types in one shot.