The employee may have been infected during a visit to Snackbaren 1985 this weekend.
General manager David Koht-Nordbye says that the test result for the other three will not be available until Sunday or Monday, and that the bathroom is therefore closed until Tuesday.
– We are very sorry that such an incident affects us, says Koht-Nordbye NRK.
A total of 14 people have been infected in an outbreak in Indre Østfold that became known on Wednesday.
The outbreak is related to travel in green countries and to the nightlife in Askim.
Koht-Nordbye confirms that the infection at Østfoldbadet can be linked to the outbreak in the municipality.