The polio virus has been detected in Melbourne's sewerage system, prompting health authorities to issue a warning about the importance of vaccinations.

The childhood disease once killed or paralysed thousands of young people each year, but a global effort to eradicate the virus has all but wiped it out.

Polio virus has been detected at the Western Treatment Plant in Werribee. Credit:Jason South

On Friday, Victoria's acting chief health officer Dr Brett Sutton announced polio had been detected in tiny concentrations as part of routine testing of pre-treated sewerage at the Western Treatment Plant in Melbourne.

However he said the discovery did not necessarily mean someone had polio.