As a rapidly increasing number of California dairy farms suffer outbreaks of H5N1 bird flu, industry experts say it remains unclear just how the disease

Five more people who presumably contracted the bird flu are being tested in California's Central Valley and are pending CDC testing.

California is investigating five possible human cases of bird flu among dairy farm workers, in addition to the six cases previously confirmed in the state, the state health department said on Monday.

Millions of migratory birds are arriving on Australian shores this spring. Any one of them could bring the new, deadly strain known as H5N1. Extra government funding will help us prepare and respond.

Biosecurity, environmental funding for protected native species and a top-up of the national stockpile of flu vaccines are part of preparations for the arrival of H5N1 to Australia.