Doctors have been notified after an outbreak of syphilis in several remote communities in Central Australia and the Northern Territory.

The Northern Territory's Centre for Disease Control sent a memo to remote clinics on January 21 saying there had been 75 infectious syphilis cases in the past year.

This is well above the 2013 figure of 44 cases, and the 30 recorded in 2012.

The memo asked doctors to offer syphilis testing to all sexually active people aged under 35.

"Health services are asked to be aware that a significant increase in the number of infectious syphilis cases has been identified in several remote communities in the Alice Springs, Katherine and Barkly regions, with linked cases occurring in Alice Springs and Katherine towns," it said.

"Contact tracing is being conducted intensively at present, so more cases are expected," it said.

Centre spokesman Dr Matthew Thalanany said young people from the ages of 13 to 19 were most at risk.

Syphilis is a sexually transmitted infection that is highly contagious in its early stages, but sufferers may not know they have it until months after infection.

If left untreated syphilis can be deadly and outbreaks have been associated with an increased incidence of in-utero death.

Syphilis has historically been higher among young people in remote Aboriginal communities but had been thought to be on the decline.

In 2013 though an outbreak occurred in part of Queensland, sparking calls for condoms to be more widely available.

"It is an illness which affect many parts of the body and body systems and although the principal mode is sexual contact it can also pass from a mother to a foetus," Dr Thalanany said.

"As a consequence of that, the baby could be lost or if the baby is born, (they) could be infected with congenital syphilis ... we really wouldn't want any baby born with a disease of this nature, when it can be treated or prevented," he said.

The centre said it was working to contain the outbreak by offering testing to patients and tracing sexual contact.