The H5N1 virus can be fatal to cats and dogs but cases are infrequent and may be mistaken for other illnesses Follow our Australia news live blog for latest updates Get our breaking news email , free app or daily news podcast The deadly H5N1 strain of bird flu has arrived on the Australian mainland and, while there’s no evidence yet of mass animal mortality, authorities are on high alert. The virus has killed millions of birds and thousands of marine mammals since it began spreading around the globe in 2021. The risk to humans is low – but should we be worried about our pets?