The pandemic is bearing down on military readiness. And with predictions that the outbreak could last for months, concerns are growing inside the Pentagon and Congress that the virus could seriously erode the military’s preparedness to fight.

The Army’s top officer on Thursday said that while he does not yet see any major impact on his forces’ ability to carry out their mission, the service needs to start planning for the longer-term implications. A top Air Force general predicted the outbreak will have serious consequences for readiness the longer it goes on. And the Pentagon is now concerned enough that it’s withholding information about which fighting units are most affected out of fear of alerting potential adversaries to weak spots.

The biggest worry is the spread of the virus itself, which on Friday hit sailors on a second aircraft carrier as the Pentagon reported military coronavirus cases among troops topped 300 — raising new questions about whether some of the military’s frontline units might not be fully prepared to respond to an attack or could be sidelined altogether.