Queensland Health says there has been a spike in mosquito-borne diseases in the Wide Bay region in the state's south, after the recent floods.
Dr Margaret Young says even though floodwater is drying out, mosquitos are still breeding.
She says cases of Ross River and Barmah Forest virus have been diagnosed in the area.
"The counts that we make represent the tip of the iceberg," she said.
"It's when disease makes someone sick enough to actually go to the doctor, blood test gets done and then the disease is reported back.
"What we count each year is the absolute confirmed cases through the laboratory and those are tracking at above normal levels now for both Barmah Forest and Ross River."
© ABC 2013
17:25 EST Farmers say Australia urgently needs a new national plan for drought, after Agriculture Department figures reveal less than half the funds allocated for Commonwealth concessional loans schemes .