Gay men are being urged to get vaccinated against meningococcal disease after a sudden outbreak in Melbourne.

Meningococcal disease: There are five main strains of meningococcal disease: A, C, W, Y and B

There are five main strains of meningococcal disease: A, C, W, Y and B The disease is uncommon but serious

The disease is uncommon but serious Meningococcal bacteria is passed on through regular close, prolonged or intimate contact with infected secretions from the back of the nose and throat

Meningococcal bacteria is passed on through regular close, prolonged or intimate contact with infected secretions from the back of the nose and throat The bacteria can develop into invasive meningococcal disease

The bacteria can develop into invasive meningococcal disease Symptoms include fever, headache, loss of appetite, nausea, neck stiffness, discomfort when looking at bright lights Source: Better Health Victoria

Health authorities are offering a free vaccine from next week after eight men were struck down with the disease's C-strain since May.

Victoria's deputy chief health officer, Brett Sutton, said almost all the patients identified as gay or bisexual.

"Eight doesn't sound like a big number, but if this were to affect the whole of Melbourne at the same rate as it's affected men who have sex with men, we'd be talking about a couple of hundred cases over a few months," he said.

"My message to this group in the community is simple: If you are vaccinated, you protect yourself and others around you by reducing the spread of the disease."

Meningococcal disease is uncommon but it can be deadly.

Authorities think the bacteria was transmitted through kissing. ( Supplied: Healthdirect.gov.au )

Ten per cent of cases are fatal within 24 to 48 hours of diagnosis.

The bacteria lives in the throat and nose and is passed on through close and prolonged contact.

"That includes intimate kissing and we think that's what's driving transmission in this outbreak," Dr Sutton said.

Patients in the high-risk group who come down with a high fever, headache and light sensitivity should see their doctor or go to hospital.

Men can get the vaccine from their local GP from Monday, December 11.