Victoria is in the midst of one of its worst outbreaks of Ross River virus in the past 25 years, with more than 1000 cases reported in six weeks.
Chief health officer Charles Guest said on Friday that doctors had reported 1012 cases since January 1.
It follows floods across the state's north and west in 2016 and a subsequent boom in mosquito numbers.
More than 120 cases have been recorded in Melbourne.
Mosquito breeding sites are being treated in 18 local government areas in an attempt to control the population.
People with Ross River virus usually have a rash and enlarged lymph nodes soon after being bitten and can suffer arthritis for up to a year.
The mosquito-borne disease commonly affects people in the northern states and outbreaks of this magnitude in Victoria have been recorded only three other times since 1993.
The most recent outbreak occurred in 2011 when 1306 people tested positive, though only 103 cases had been recorded by mid-February.
Queensland often has more than 2000 cases each year with more than 6000 infected in 2015, when the state's southeast flooded.
People experiencing symptoms of the virus should seek immediate medical attention from their GP or local hospital.
TIPS FOR PROTECTING YOURSELF FROM MOSQUITOES
* Check insect screens on doors and windows for tears or gaps.
* Wear long, light-coloured, loose-fitting clothing and apply a repellent containing picaridin or DEET to areas of exposed skin.
* Empty water from containers, old tyres, unused fish ponds and pot plant holders at least once a week.
Source: Victorian Health Department
© AAP 2017