The 49ers announced on Monday they’ve placed standout linebacker Fred Warner on the reserve/COVID-19 list. He’s one of just five NFL players currently on the list.

Warner joins Richie James Jr. and Jeff Wilson Jr. as the three 49ers players who have found themselves on the list since training camp started. Both James — who is injured — and Wilson have since been activated.

The designation means Warner either tested positive for COVID-19 or was exposed to someone who had the virus. Warner will be required to isolate at home, and can return when he is “medically cleared,” whenever that may be.

The 49ers’ regular season opener vs. the Cardinals is scheduled for two weeks from now, which is around how long it takes for someone who has contracted the virus to no longer be contagious.