Health authorities are warning visitors to the Surf Coast, Geelong and Bellarine Peninsula to protect themselves against mosquito-born diseases.
It comes after Ross River virus was detected in mosquitoes in Anglesea.
With a stretch of days over 30 degrees on the horizon, thousands of people are expected to flock to the beach.
People along the coast are being warned to avoid mosquito bites by using repellents with DEET or picaridin on all exposed skin, wearing long, loose-fitting clothing while outside, and ensuring accommodation is properly fitted with mosquito nets and screens.
The warning is against both Ross River virus and Barmah Forest virus.
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Joint pain and stiffness, headache, fever, rash and fatigue are among the symptoms of both viruses.
Doctors are being advised to consider the possibility of mosquito-borne disease in patients with relevant symptoms, especially after travel to rural or regional Victoria.
There is a risk of Ross River virus infection in all parts of Victoria where there are mosquitoes.
However, health advice said the risk was greatest in rural and regional areas. Infection in outer metropolitan areas appeared to be rare.
Health authorities warned of the risk of Ross River virus in the state's south-west in December, after the virus was detected in mosquitoes in urban Mildura.
The warning was expanded to Geelong, the Surf Coast and Bellarine Peninsula just before Christmas, after mosquitoes in Anglesea were found to be carrying Ross River virus.