Another case of measles has been diagnosed in Victoria, this time for a person who spent several hours at Melbourne airport.

Health authorities say the illness was acquired overseas and the affected person was in transit through Melbourne Airport for several hours on Tuesday, March 19.

Victoria's chief health officer, Dr Brett Sutton, said the case is unrelated to any of the eight previous measles cases notified to the health department this year.

In the most recent case, the affected person travelled on flight JQ517 from Sydney to Melbourne and was at Melbourne Airport terminals two and four from 3.30pm until 7pm.

The person also boarded flight VA99 from Melbourne to Christchurch between 6.35pm and 11.35pm.

Dr Sutton said anyone who is unvaccinated is at highest risk of contracting measles.

"People need to have received two doses of measles-containing vaccine to be fully protected. Many adults have only received one vaccine against measles and therefore most cases are in this age group," he said.

Most people born before 1966 will have been exposed to measles in childhood and will therefore be protected.

However, adults born in or after 1966 may be susceptible, especially if overseas travel is planned, and should go to their doctor for a free vaccination.

"There is a lot of measles circulating in our region currently, including much of south east and southern Asia. All travellers need to be aware of this risk," Dr Sutton said.