This case series shows how COVID-19 can spread and be contained in close environments.

Researchers conducted a retrospective review of COVID-19 cases in Swiss Armed Forces recruits in the early weeks of the pandemic. Both PCR and serological testing were performed.

A first case was likely infected while skiing off base. He became symptomatic 4 days later, tested positive by PCR, was put into isolation, and was asymptomatic after 48 hours. All close contacts int he past two days were quarantined, involving 55 of the 140 recruits in the company. Seven out of nine recruits in one quarantine room became mildly symptomatic, and one of them became positive by PCR. After a week, both cases still tested positive by PCE, even though they had been completely asymptomatic for over four days. Serological testing was positive for both patients, and negative for everyone else.