Last Sunday news began to surface about dozens of passengers and about 15 crew members falling ill while on the Baltic cruise ship Silja Symphony.
Since then, the Estonia-based firm Tallink Silja managed to track down the source of the illnesses on the ship. According to tests by the National Institute for Health and Welfare, THL, the culprit turned out to be what they expected: norovirus.
Despite finding the source – and scrubbing down the ship's surfaces with disinfectants – passenger illnesses continue, according to Tallink Silja's communications chief, Marika Nöjd.
"New cases keep popping up regularly," Nöjd said. "Last (Wednesday) night was quiet but this morning we learned that four crew members and one passenger had become sick."
Nöjd said that a total of 150 people have been affected so far.
"We hope the epidemic will subside soon," she said.
Typical symptoms of norovirus infection include nausea, stomach pain, vomiting and diarrhoea.
THL confirms norovirus
THL, which on Thursday confirmed that the illness outbreak was due to norovirus, said it has yet to find the exact source of the virus.
Meanwhile the cleaning and disinfection of the ship continues, and the ferry has temporarily closed the children's play area and staff gym.
Silja's passenger terminals in Helsinki and Stockholm, Sweden are also being thoroughly cleaned, the company said.
The passenger and car ferry Silja Symphony cruises between Helsinki, Mariehamn, Åland and Stockholm.