A man in his 80s died in a Sydney hospital after testing positive to COVID-19, becoming the third coronavirus-related casualty in Australia, state health authorities said on Sunday.The total number of coronavirus cases has topped 70 in Australia with state and federal health authorities fretting over the risk of more widespread community transmission.The outbreak has killed more than 3,400 people worldwide, spreading across more than 90 nations outside China.New South Wales Health said in a…