Cases of the potentially fatal disease syphilis have almost doubled in the North West in two years, figures show.
Health experts are continuing to promote the safe sex message
The Health Protection Agency (HPA) is contacting doctors and dentists to ask them to look out for early symptoms of the sexually transmitted infection.
Syphilis was almost eradicated in the UK, but cases are now rising rapidly.
In the North West, half of the 499 reported cases in 2005 were at three Manchester clinics. Preston, Blackpool and Southport also had large numbers.
Figures from the HPA North West show that in 2003, 261 cases were reported, rising to 244 in 2004 and almost 500 last year. The majority of those diagnosed were gay men.
SYPHILIS CASES IN THE NORTH WEST IN 2005
Merseyside and Cheshire 68
Cumbria and Lancashire 104
Greater Manchester 327
There were only 333 diagnosed cases of syphilis in the whole of the UK in 2000. The figure rose to 2,807 in 2005.
Dr Lorraine Lighton, the HPA regional sexual health lead, said: "We saw a surge in syphilis across the country last year, largely driven by outbreaks in Manchester and London.
"In response, we at HPA North West are strengthening our surveillance and we are reminding doctors and dentists across the region of the symptoms to look out for.
"Syphilis was so rare when most practising doctors were at medical school that it is not likely to be the first thing to spring to mind when a GP is confronted with a patient who has early symptoms, which might be no more than a skin rash initially."
Many of those diagnosed with the disease also had another STI and 138 were HIV positive.
"Many people with syphilis will have no obvious symptoms, so this is a particular challenge for health services," Dr Lighton said.
Initial symptoms include genital sores. If the infection is not treated, a rash may appear, with flu-like symptoms.
Once the sores and rash have cleared up, there may be no symptoms for many years.
Latent syphilis can develop about 10 years after first infection, causing serious damage to the heart, brain, eyes, internal organs and nervous system and can be fatal.
Dr Lighton said: "When you add gonorrhoea and chlamydia to the mix of diseases, we have a major problem on our hands.
"We can only keep reminding people about the risks of unprotected sex and that they can protect themselves against sexually transmitted infections by using condoms."