According to Aftonbladet, he remained absent on Wednesday afternoon and stayed at the team hotel, with mild symptoms reported and no specifics disclosed.
The left-back had only just returned after five weeks out with a hamstring injury suffered in April’s FA Cup semi-final defeat to Chelsea at Wembley.
He is head coach Graham Potter’s preferred option at left wing-back and started both World Cup qualifying play-off games.
Sweden open against Tunisia in Guadalupe, Mexico on June 15, then face the Netherlands in Houston, Texas five days later, before meeting Ao Tanaka’s Japan in Arlington on June 26.