Syphilis has reached its highest level ever recorded in Australia, with the increase almost exclusively among gay men.
Health experts are calling for an increased focus on syphilis after data showed 1765 people were diagnosed with the potentially deadly bacterial disease in Australia last year - a 34 per cent increase on the number documented in 2009.
The annual surveillance report on the nation's sexual health produced by the University of NSW's Kirby Institute said unprotected sex between men was the main driver of new diagnoses between 2009 and 2013.
Associate Professor David Wilson, one of the authors of the report that looked at viral hepatitis and sexually transmissible infections (STI) in Australia, said syphilis remains far less common in Australia than many other sexually transmitted diseases.
But there has been a rise in men catching the disease and this is due to the increase in condomless sex between men, he said.
Syphilis is increasing almost exclusively amongst gay men and men who have sex with men, he said.
What we have seen is there have been decreases in condom use in that population, that's likely to be one of the key reasons for that.
Professor John de Wit, director of UNSW's Centre for Social Research in Health, said people tend to think of syphilis as an old and rare disease, which is not helpful.
Indeed syphilis does have this image of being one of those classical venereal diseases from a bygone era and that is not very helpful, he said.
If syphilis is not diagnosed it can have a significant impact on people's health.
Symptoms of late stage syphilis include difficulty coordinating muscle movements, paralysis, numbness, blindness, and dementia.
In the late stages of syphilis, the disease damages the internal organs and can result in death.
Other statistics include the finding that the number of people dying from liver disease related to hepatitis C, which is transmitted through blood to blood contact, has more than doubled in a decade.
Over 10,000 people are diagnosed with the virus that causes inflammation of the liver each year.
Around 630 Australians died from hepatitis C-related liver failure and liver cancer in 2013.
Hepatitis C is a very serious health issue that is very much in need of more public and policy attention, said Prof de Wit.
The report, released on Thursday as part of the 9th Australasian Viral Hepatitis Conference in Alice Springs, also showed gonorrhoea rates have increased .
In 2013, there were 14,947 new diagnoses of the STI, commonly called the 'clap', up 81 per cent in the past five years.
However, in good news, the surveillance report said chlamydia rates have slightly declined for the first time in recent history, although it remains the most common STI.
Last year, there were 82,537 new cases of the infection, which can cause permanent damage to a woman's reproductive system.
Cases of genital warts among women have also dropped dramatically due to the introduction of the Human Papillomavirus (HPV) vaccination program in 2007, according to the report.