A rampant summer of Ross River fever is set to extend into autumn, with high tides and predicted warm weather expected to cause a fresh outbreak of the mosquito-borne virus in time for the Easter holidays.

The virus has infected NSW residents at a rate seven times higher than last year, with 539 notifications in the year to date, compared with 79 this time last year.

NSW Health issued its second alert of the year on Wednesday warning people to take extra precautions to avoid becoming infected.

Director of Communicable Diseases Dr Vicky Sheppeard said the next few weeks, when many people would be spending the Easter break outdoors, were ideal breeding conditions for mosquitoes.

"Autumn is the peak time of the year for these insects to carry such infections so it is also when there is the highest number of mosquito-borne viral infections," she said.