The WHO has confirmed that 4 bird flu cases reported in Pakistan in December 2007 were likely a family cluster. That means that the bird flu virus was spread from one person to another. WHO calls this "limited human-to-human transmission" because it involves the spread of the disease among very close contacts. The disease has not spread into the community. Pakistan has had many cases of bird flu in poultry, but relatively few reported cases of the H5N1 bird flu virus in humans.