Understanding how the virus is infecting cows and how the disease progresses in the animals is essential to developing therapeutics, like vaccines. Since then, there have been 172 confirmed cases of infected dairy milking cows in 13 states. The USDA scientists’ animal challenge study showing that field infections of H5N1 can be replicated under laboratory conditions is detailed in a paper that will be submitted for publication in a peer-reviewed journal. In the second study, the mammary exposed lactating cows became infected and displayed symptoms within 48 hours of infection. Specific knowledge gaps that reliable, repeatable animal challenge methods can help answer are:Tropisms of the virus within the body over time.