Already, the outbreak has placed significant strain on the stores of masks, medicine, and medical equipment. The stockpile has been called on to help with efforts to repatriate and quarantine Americans flown back from China and Japan, but has come under fire for a perceived shortage of masks — and for allowing millions of masks already in its stock to pass their expiration dates.

In an interview, the stockpile’s acting director Steven Adams reiterated that the SNS stocks roughly 13 million N95 masks — though health secretary Alex Azar has told lawmakers that as many as 5 million may be expired.

Adams said the federal government updated guidelines on March 1 clarifying that many older masks were still usable. All supplies in the current SNS store, a spokeswoman said, are in good working order. Adams also emphasized that the federal government had recently ordered 500 million more masks.