People holidaying on the Victoria/NSW border have an extra reason to avoid "public enemy number one" - mosquitoes, which may be carrying a serious virus.
Heavy rain in both Victoria and NSW has led to a significant increase in the number of the bugs around, with some mosquito-borne viruses detected.
Victorian health authorities on Friday warned residents and visitors along the Murray River in the state's north to take extra measures to avoid mosquito bites.
A NSW Health warning issued this week applies across the state, with autumn the peak time for mosquito-borne viral infections.
Victoria's deputy chief health officer Dr Michael Ackland said the Murray Valley Encephalitis (MVE) virus has been detected in sentinel chicken flocks - used to test for mosquito-borne viruses - in Deniliquin near the Victorian border.
A similar disease, Kunjin virus, has been detected in a flock in another NSW Riverina town, Leeton.
NSW Health says the state's monitoring program has also picked up Ross River virus and Barmah Forest virus in mosquitoes in many parts of the state including Sydney.
NSW Health director of communicable diseases Dr Vicky Sheppeard said the next few weeks will be ideal breeding conditions for mosquitoes carrying the Ross River and Barmah Forest viruses, and possibly even the more serious viruses such as Kunjin and MVE.
She said the number of cases of people having mosquito-borne infections have not been very high so far this year, with 116 Ross River cases and 59 of Barmah Forest virus.
"Case numbers usually rise in the autumn months, particularly with the kind of weather conditions we have seen this year," she said.
"There is no specific treatment for these viruses. The best way to avoid infection is to avoid being bitten by mosquitoes."
Dr Ackland said no viruses had been detected in nine Victorian flocks this summer but testing continued.
