yes, but they are not the same species of mammals as other mammals. diseases exist which affect mammals like dogs, and cows, which do not affect humans, and are not passed between the mammal species. H5N1 has not been seen to have been transmitted to humans from another mammal species before this, making the danger of inter-human species transmission (read: pandemic) far greater and more likely than it's been up until now when it was solely transmitted to humans from birds.