A fourth case of meningitis has been confirmed in the north.
The new patient is a parent of a scout who was at 23rd World Scout Jamboree in Japan, which has been at the centre of the outbreak.
The adult has been admitted to hospital and is receiving treatment.
However Health Protection Scotland (HPS) said the parent is not related to any of the previous three cases diagnosed last week.
A small number of household contacts have been offered antibiotics and vaccination as a precautionary measure.
One confirmed case of meningococcal disease and two suspected cases have also emerged in Sweden. The affected people are also understood to be scouts at the Asian event.
HPS is now trying to ascertain any links between the scouts in the two countries.
Last week Inverness teenager Brodie McMaster spent two days in hospital after falling ill with meningitis.
He was part of a 40-strong group of children and adults from the north and north-east who went to Japan for the 12-day event.
They flew back to Scotland on August 8 and Brodie and another boy were diagnosed on Tuesday.
A third Highland case was confirmed on Thursday.
HPS said it is in contact with colleagues in Japan, the World Health Organisation and the European Centre for Disease Prevention and Control and is unaware of any other cases associated with the jamboree apart from Scotland and Sweden.
Dr Jim McMenamin, consultant epidemiologist and chairman of the incident team said: “This patient is a close contact of a scout who recently attended the jamboree. They followed the advice given and when they began to feel unwell, contacted medical services and were rapidly assessed and received prompt antibiotic treatment. This treatment continues in hospital.
“The early alert to the international medical agencies and the scouting movement is ensuring that there is rapid identification of any suspect cases, as has been seen in Sweden.”