An outbreak of the flood-borne disease, melioidosis, has killed one person and 10 more are sick in north Queensland.

One person is dead and another 10 are sick from flood-related illnesses in Townsville following a once-in-a-century monsoonal deluge.

The cause is melioidosis, which stems from floodwaters that are heavily contaminated with dirt and bacteria, Queensland Health's Julie Mudd says in a statement on Tuesday.

"Given the scale of the flooding we are expecting to see increasing numbers of a range of infections, not just melioidosis," Dr Mudd said.

Melioidosis and many infections that stem from flooding can more severely affect people who are unwell or elderly or have existing chronic conditions, she warned.

Floodwater is heavily contaminated with dirt and bacteria so people are being warned to ensure it doesn't get into the body through cuts and scratches.

Two men drowned at the peak of the floods in Townsville and police are still searching for a 35-year-old man who disappeared in floodwaters at Groper Creek on Friday.